3.0.8
This project provides an API Gateway built on top of the Spring Ecosystem, including: Spring 5, Spring Boot 2 and Project Reactor. Spring Cloud Gateway aims to provide a simple, yet effective way to route to APIs and provide cross cutting concerns to them such as: security, monitoring/metrics, and resiliency.
1. How to Include Spring Cloud Gateway
To include Spring Cloud Gateway in your project, use the starter with a group ID of org.springframework.cloud
and an artifact ID of spring-cloud-starter-gateway
.
See the Spring Cloud Project page for details on setting up your build system with the current Spring Cloud Release Train.
If you include the starter, but you do not want the gateway to be enabled, set spring.cloud.gateway.enabled=false
.
Spring Cloud Gateway is built on Spring Boot 2.x, Spring WebFlux, and Project Reactor. As a consequence, many of the familiar synchronous libraries (Spring Data and Spring Security, for example) and patterns you know may not apply when you use Spring Cloud Gateway. If you are unfamiliar with these projects, we suggest you begin by reading their documentation to familiarize yourself with some of the new concepts before working with Spring Cloud Gateway. |
Spring Cloud Gateway requires the Netty runtime provided by Spring Boot and Spring Webflux. It does not work in a traditional Servlet Container or when built as a WAR. |
2. Glossary
-
Route: The basic building block of the gateway. It is defined by an ID, a destination URI, a collection of predicates, and a collection of filters. A route is matched if the aggregate predicate is true.
-
Predicate: This is a Java 8 Function Predicate. The input type is a Spring Framework
ServerWebExchange
. This lets you match on anything from the HTTP request, such as headers or parameters. -
Filter: These are instances of
GatewayFilter
that have been constructed with a specific factory. Here, you can modify requests and responses before or after sending the downstream request.
3. How It Works
The following diagram provides a high-level overview of how Spring Cloud Gateway works:
![Spring Cloud Gateway Diagram](./images/spring_cloud_gateway_diagram.png)
Clients make requests to Spring Cloud Gateway. If the Gateway Handler Mapping determines that a request matches a route, it is sent to the Gateway Web Handler. This handler runs the request through a filter chain that is specific to the request. The reason the filters are divided by the dotted line is that filters can run logic both before and after the proxy request is sent. All “pre” filter logic is executed. Then the proxy request is made. After the proxy request is made, the “post” filter logic is run.
URIs defined in routes without a port get default port values of 80 and 443 for the HTTP and HTTPS URIs, respectively. |
4. Configuring Route Predicate Factories and Gateway Filter Factories
There are two ways to configure predicates and filters: shortcuts and fully expanded arguments. Most examples below use the shortcut way.
The name and argument names will be listed as code
in the first sentance or two of the each section. The arguments are typically listed in the order that would be needed for the shortcut configuration.
4.1. Shortcut Configuration
Shortcut configuration is recognized by the filter name, followed by an equals sign (=
), followed by argument values separated by commas (,
).
spring:
cloud:
gateway:
routes:
- id: after_route
uri: https://example.org
predicates:
- Cookie=mycookie,mycookievalue
The previous sample defines the Cookie
Route Predicate Factory with two arguments, the cookie name, mycookie
and the value to match mycookievalue
.
4.2. Fully Expanded Arguments
Fully expanded arguments appear more like standard yaml configuration with name/value pairs. Typically, there will be a name
key and an args
key. The args
key is a map of key value pairs to configure the predicate or filter.
spring:
cloud:
gateway:
routes:
- id: after_route
uri: https://example.org
predicates:
- name: Cookie
args:
name: mycookie
regexp: mycookievalue
This is the full configuration of the shortcut configuration of the Cookie
predicate shown above.
5. Route Predicate Factories
Spring Cloud Gateway matches routes as part of the Spring WebFlux HandlerMapping
infrastructure.
Spring Cloud Gateway includes many built-in route predicate factories.
All of these predicates match on different attributes of the HTTP request.
You can combine multiple route predicate factories with logical and
statements.
5.1. The After Route Predicate Factory
The After
route predicate factory takes one parameter, a datetime
(which is a java ZonedDateTime
).
This predicate matches requests that happen after the specified datetime.
The following example configures an after route predicate:
spring:
cloud:
gateway:
routes:
- id: after_route
uri: https://example.org
predicates:
- After=2017-01-20T17:42:47.789-07:00[America/Denver]
This route matches any request made after Jan 20, 2017 17:42 Mountain Time (Denver).
5.2. The Before Route Predicate Factory
The Before
route predicate factory takes one parameter, a datetime
(which is a java ZonedDateTime
).
This predicate matches requests that happen before the specified datetime
.
The following example configures a before route predicate:
spring:
cloud:
gateway:
routes:
- id: before_route
uri: https://example.org
predicates:
- Before=2017-01-20T17:42:47.789-07:00[America/Denver]
This route matches any request made before Jan 20, 2017 17:42 Mountain Time (Denver).
5.3. The Between Route Predicate Factory
The Between
route predicate factory takes two parameters, datetime1
and datetime2
which are java ZonedDateTime
objects.
This predicate matches requests that happen after datetime1
and before datetime2
.
The datetime2
parameter must be after datetime1
.
The following example configures a between route predicate:
spring:
cloud:
gateway:
routes:
- id: between_route
uri: https://example.org
predicates:
- Between=2017-01-20T17:42:47.789-07:00[America/Denver], 2017-01-21T17:42:47.789-07:00[America/Denver]
This route matches any request made after Jan 20, 2017 17:42 Mountain Time (Denver) and before Jan 21, 2017 17:42 Mountain Time (Denver). This could be useful for maintenance windows.
5.4. The Cookie Route Predicate Factory
The Cookie
route predicate factory takes two parameters, the cookie name
and a regexp
(which is a Java regular expression).
This predicate matches cookies that have the given name and whose values match the regular expression.
The following example configures a cookie route predicate factory:
spring:
cloud:
gateway:
routes:
- id: cookie_route
uri: https://example.org
predicates:
- Cookie=chocolate, ch.p
This route matches requests that have a cookie named chocolate
whose value matches the ch.p
regular expression.
5.5. The Header Route Predicate Factory
The Header
route predicate factory takes two parameters, the header
and a regexp
(which is a Java regular expression).
This predicate matches with a header that has the given name whose value matches the regular expression.
The following example configures a header route predicate:
spring:
cloud:
gateway:
routes:
- id: header_route
uri: https://example.org
predicates:
- Header=X-Request-Id, \d+
This route matches if the request has a header named X-Request-Id
whose value matches the \d+
regular expression (that is, it has a value of one or more digits).
5.6. The Host Route Predicate Factory
The Host
route predicate factory takes one parameter: a list of host name patterns
.
The pattern is an Ant-style pattern with .
as the separator.
This predicates matches the Host
header that matches the pattern.
The following example configures a host route predicate:
spring:
cloud:
gateway:
routes:
- id: host_route
uri: https://example.org
predicates:
- Host=**.somehost.org,**.anotherhost.org
URI template variables (such as {sub}.myhost.org
) are supported as well.
This route matches if the request has a Host
header with a value of www.somehost.org
or beta.somehost.org
or www.anotherhost.org
.
This predicate extracts the URI template variables (such as sub
, defined in the preceding example) as a map of names and values and places it in the ServerWebExchange.getAttributes()
with a key defined in ServerWebExchangeUtils.URI_TEMPLATE_VARIABLES_ATTRIBUTE
.
Those values are then available for use by GatewayFilter
factories
5.7. The Method Route Predicate Factory
The Method
Route Predicate Factory takes a methods
argument which is one or more parameters: the HTTP methods to match.
The following example configures a method route predicate:
spring:
cloud:
gateway:
routes:
- id: method_route
uri: https://example.org
predicates:
- Method=GET,POST
This route matches if the request method was a GET
or a POST
.
5.8. The Path Route Predicate Factory
The Path
Route Predicate Factory takes two parameters: a list of Spring PathMatcher
patterns
and an optional flag called matchTrailingSlash
(defaults to true
).
The following example configures a path route predicate:
spring:
cloud:
gateway:
routes:
- id: path_route
uri: https://example.org
predicates:
- Path=/red/{segment},/blue/{segment}
This route matches if the request path was, for example: /red/1
or /red/1/
or /red/blue
or /blue/green
.
If matchTrailingSlash
is set to false
, then request path /red/1/
will not be matched.
This predicate extracts the URI template variables (such as segment
, defined in the preceding example) as a map of names and values and places it in the ServerWebExchange.getAttributes()
with a key defined in ServerWebExchangeUtils.URI_TEMPLATE_VARIABLES_ATTRIBUTE
.
Those values are then available for use by GatewayFilter
factories
A utility method (called get
) is available to make access to these variables easier.
The following example shows how to use the get
method:
Map<String, String> uriVariables = ServerWebExchangeUtils.getPathPredicateVariables(exchange);
String segment = uriVariables.get("segment");
5.9. The Query Route Predicate Factory
The Query
route predicate factory takes two parameters: a required param
and an optional regexp
(which is a Java regular expression).
The following example configures a query route predicate:
spring:
cloud:
gateway:
routes:
- id: query_route
uri: https://example.org
predicates:
- Query=green
The preceding route matches if the request contained a green
query parameter.
spring:
cloud:
gateway:
routes:
- id: query_route
uri: https://example.org
predicates:
- Query=red, gree.
The preceding route matches if the request contained a red
query parameter whose value matched the gree.
regexp, so green
and greet
would match.
5.10. The RemoteAddr Route Predicate Factory
The RemoteAddr
route predicate factory takes a list (min size 1) of sources
, which are CIDR-notation (IPv4 or IPv6) strings, such as 192.168.0.1/16
(where 192.168.0.1
is an IP address and 16
is a subnet mask).
The following example configures a RemoteAddr route predicate:
spring:
cloud:
gateway:
routes:
- id: remoteaddr_route
uri: https://example.org
predicates:
- RemoteAddr=192.168.1.1/24
This route matches if the remote address of the request was, for example, 192.168.1.10
.
5.11. The Weight Route Predicate Factory
The Weight
route predicate factory takes two arguments: group
and weight
(an int). The weights are calculated per group.
The following example configures a weight route predicate:
spring:
cloud:
gateway:
routes:
- id: weight_high
uri: https://weighthigh.org
predicates:
- Weight=group1, 8
- id: weight_low
uri: https://weightlow.org
predicates:
- Weight=group1, 2
This route would forward ~80% of traffic to weighthigh.org and ~20% of traffic to weighlow.org
5.11.1. Modifying the Way Remote Addresses Are Resolved
By default, the RemoteAddr route predicate factory uses the remote address from the incoming request. This may not match the actual client IP address if Spring Cloud Gateway sits behind a proxy layer.
You can customize the way that the remote address is resolved by setting a custom RemoteAddressResolver
.
Spring Cloud Gateway comes with one non-default remote address resolver that is based off of the X-Forwarded-For header, XForwardedRemoteAddressResolver
.
XForwardedRemoteAddressResolver
has two static constructor methods, which take different approaches to security:
-
XForwardedRemoteAddressResolver::trustAll
returns aRemoteAddressResolver
that always takes the first IP address found in theX-Forwarded-For
header. This approach is vulnerable to spoofing, as a malicious client could set an initial value for theX-Forwarded-For
, which would be accepted by the resolver. -
XForwardedRemoteAddressResolver::maxTrustedIndex
takes an index that correlates to the number of trusted infrastructure running in front of Spring Cloud Gateway. If Spring Cloud Gateway is, for example only accessible through HAProxy, then a value of 1 should be used. If two hops of trusted infrastructure are required before Spring Cloud Gateway is accessible, then a value of 2 should be used.
Consider the following header value:
X-Forwarded-For: 0.0.0.1, 0.0.0.2, 0.0.0.3
The following maxTrustedIndex
values yield the following remote addresses:
maxTrustedIndex |
result |
---|---|
[ |
(invalid, |
1 |
0.0.0.3 |
2 |
0.0.0.2 |
3 |
0.0.0.1 |
[4, |
0.0.0.1 |
The following example shows how to achieve the same configuration with Java:
RemoteAddressResolver resolver = XForwardedRemoteAddressResolver
.maxTrustedIndex(1);
...
.route("direct-route",
r -> r.remoteAddr("10.1.1.1", "10.10.1.1/24")
.uri("https://downstream1")
.route("proxied-route",
r -> r.remoteAddr(resolver, "10.10.1.1", "10.10.1.1/24")
.uri("https://downstream2")
)
6. GatewayFilter
Factories
Route filters allow the modification of the incoming HTTP request or outgoing HTTP response in some manner. Route filters are scoped to a particular route. Spring Cloud Gateway includes many built-in GatewayFilter Factories.
For more detailed examples of how to use any of the following filters, take a look at the unit tests. |
6.1. The AddRequestHeader
GatewayFilter
Factory
The AddRequestHeader
GatewayFilter
factory takes a name
and value
parameter.
The following example configures an AddRequestHeader
GatewayFilter
:
spring:
cloud:
gateway:
routes:
- id: add_request_header_route
uri: https://example.org
filters:
- AddRequestHeader=X-Request-red, blue
This listing adds X-Request-red:blue
header to the downstream request’s headers for all matching requests.
AddRequestHeader
is aware of the URI variables used to match a path or host.
URI variables may be used in the value and are expanded at runtime.
The following example configures an AddRequestHeader
GatewayFilter
that uses a variable:
spring:
cloud:
gateway:
routes:
- id: add_request_header_route
uri: https://example.org
predicates:
- Path=/red/{segment}
filters:
- AddRequestHeader=X-Request-Red, Blue-{segment}
6.2. The AddRequestParameter
GatewayFilter
Factory
The AddRequestParameter
GatewayFilter
Factory takes a name
and value
parameter.
The following example configures an AddRequestParameter
GatewayFilter
:
spring:
cloud:
gateway:
routes:
- id: add_request_parameter_route
uri: https://example.org
filters:
- AddRequestParameter=red, blue
This will add red=blue
to the downstream request’s query string for all matching requests.
AddRequestParameter
is aware of the URI variables used to match a path or host.
URI variables may be used in the value and are expanded at runtime.
The following example configures an AddRequestParameter
GatewayFilter
that uses a variable:
spring:
cloud:
gateway:
routes:
- id: add_request_parameter_route
uri: https://example.org
predicates:
- Host: {segment}.myhost.org
filters:
- AddRequestParameter=foo, bar-{segment}
6.3. The AddResponseHeader
GatewayFilter
Factory
The AddResponseHeader
GatewayFilter
Factory takes a name
and value
parameter.
The following example configures an AddResponseHeader
GatewayFilter
:
spring:
cloud:
gateway:
routes:
- id: add_response_header_route
uri: https://example.org
filters:
- AddResponseHeader=X-Response-Red, Blue
This adds X-Response-Foo:Bar
header to the downstream response’s headers for all matching requests.
AddResponseHeader
is aware of URI variables used to match a path or host.
URI variables may be used in the value and are expanded at runtime.
The following example configures an AddResponseHeader
GatewayFilter
that uses a variable:
spring:
cloud:
gateway:
routes:
- id: add_response_header_route
uri: https://example.org
predicates:
- Host: {segment}.myhost.org
filters:
- AddResponseHeader=foo, bar-{segment}
6.4. The DedupeResponseHeader
GatewayFilter
Factory
The DedupeResponseHeader GatewayFilter factory takes a name
parameter and an optional strategy
parameter. name
can contain a space-separated list of header names.
The following example configures a DedupeResponseHeader
GatewayFilter
:
spring:
cloud:
gateway:
routes:
- id: dedupe_response_header_route
uri: https://example.org
filters:
- DedupeResponseHeader=Access-Control-Allow-Credentials Access-Control-Allow-Origin
This removes duplicate values of Access-Control-Allow-Credentials
and Access-Control-Allow-Origin
response headers in cases when both the gateway CORS logic and the downstream logic add them.
The DedupeResponseHeader
filter also accepts an optional strategy
parameter.
The accepted values are RETAIN_FIRST
(default), RETAIN_LAST
, and RETAIN_UNIQUE
.
6.5. Spring Cloud CircuitBreaker GatewayFilter Factory
The Spring Cloud CircuitBreaker GatewayFilter factory uses the Spring Cloud CircuitBreaker APIs to wrap Gateway routes in a circuit breaker. Spring Cloud CircuitBreaker supports multiple libraries that can be used with Spring Cloud Gateway. Spring Cloud supports Resilience4J out of the box.
To enable the Spring Cloud CircuitBreaker filter, you need to place spring-cloud-starter-circuitbreaker-reactor-resilience4j
on the classpath.
The following example configures a Spring Cloud CircuitBreaker GatewayFilter
:
spring:
cloud:
gateway:
routes:
- id: circuitbreaker_route
uri: https://example.org
filters:
- CircuitBreaker=myCircuitBreaker
To configure the circuit breaker, see the configuration for the underlying circuit breaker implementation you are using.
The Spring Cloud CircuitBreaker filter can also accept an optional fallbackUri
parameter.
Currently, only forward:
schemed URIs are supported.
If the fallback is called, the request is forwarded to the controller matched by the URI.
The following example configures such a fallback:
spring:
cloud:
gateway:
routes:
- id: circuitbreaker_route
uri: lb://backing-service:8088
predicates:
- Path=/consumingServiceEndpoint
filters:
- name: CircuitBreaker
args:
name: myCircuitBreaker
fallbackUri: forward:/inCaseOfFailureUseThis
- RewritePath=/consumingServiceEndpoint, /backingServiceEndpoint
The following listing does the same thing in Java:
@Bean
public RouteLocator routes(RouteLocatorBuilder builder) {
return builder.routes()
.route("circuitbreaker_route", r -> r.path("/consumingServiceEndpoint")
.filters(f -> f.circuitBreaker(c -> c.name("myCircuitBreaker").fallbackUri("forward:/inCaseOfFailureUseThis"))
.rewritePath("/consumingServiceEndpoint", "/backingServiceEndpoint")).uri("lb://backing-service:8088")
.build();
}
This example forwards to the /inCaseofFailureUseThis
URI when the circuit breaker fallback is called.
Note that this example also demonstrates the (optional) Spring Cloud LoadBalancer load-balancing (defined by the lb
prefix on the destination URI).
The primary scenario is to use the fallbackUri
to define an internal controller or handler within the gateway application.
However, you can also reroute the request to a controller or handler in an external application, as follows:
spring:
cloud:
gateway:
routes:
- id: ingredients
uri: lb://ingredients
predicates:
- Path=//ingredients/**
filters:
- name: CircuitBreaker
args:
name: fetchIngredients
fallbackUri: forward:/fallback
- id: ingredients-fallback
uri: http://localhost:9994
predicates:
- Path=/fallback
In this example, there is no fallback
endpoint or handler in the gateway application.
However, there is one in another application, registered under localhost:9994
.
In case of the request being forwarded to fallback, the Spring Cloud CircuitBreaker Gateway filter also provides the Throwable
that has caused it.
It is added to the ServerWebExchange
as the ServerWebExchangeUtils.CIRCUITBREAKER_EXECUTION_EXCEPTION_ATTR
attribute that can be used when handling the fallback within the gateway application.
For the external controller/handler scenario, headers can be added with exception details. You can find more information on doing so in the FallbackHeaders GatewayFilter Factory section.
6.5.1. Tripping The Circuit Breaker On Status Codes
In some cases you might want to trip a circuit breaker based on the status code
returned from the route it wraps. The circuit breaker config object takes a list of
status codes that if returned will cause the the circuit breaker to be tripped. When setting the
status codes you want to trip the circuit breaker you can either use a integer with the status code
value or the String representation of the HttpStatus
enumeration.
spring:
cloud:
gateway:
routes:
- id: circuitbreaker_route
uri: lb://backing-service:8088
predicates:
- Path=/consumingServiceEndpoint
filters:
- name: CircuitBreaker
args:
name: myCircuitBreaker
fallbackUri: forward:/inCaseOfFailureUseThis
statusCodes:
- 500
- "NOT_FOUND"
@Bean
public RouteLocator routes(RouteLocatorBuilder builder) {
return builder.routes()
.route("circuitbreaker_route", r -> r.path("/consumingServiceEndpoint")
.filters(f -> f.circuitBreaker(c -> c.name("myCircuitBreaker").fallbackUri("forward:/inCaseOfFailureUseThis").addStatusCode("INTERNAL_SERVER_ERROR"))
.rewritePath("/consumingServiceEndpoint", "/backingServiceEndpoint")).uri("lb://backing-service:8088")
.build();
}
6.6. The FallbackHeaders
GatewayFilter
Factory
The FallbackHeaders
factory lets you add Spring Cloud CircuitBreaker execution exception details in the headers of a request forwarded to a fallbackUri
in an external application, as in the following scenario:
spring:
cloud:
gateway:
routes:
- id: ingredients
uri: lb://ingredients
predicates:
- Path=//ingredients/**
filters:
- name: CircuitBreaker
args:
name: fetchIngredients
fallbackUri: forward:/fallback
- id: ingredients-fallback
uri: http://localhost:9994
predicates:
- Path=/fallback
filters:
- name: FallbackHeaders
args:
executionExceptionTypeHeaderName: Test-Header
In this example, after an execution exception occurs while running the circuit breaker, the request is forwarded to the fallback
endpoint or handler in an application running on localhost:9994
.
The headers with the exception type, message and (if available) root cause exception type and message are added to that request by the FallbackHeaders
filter.
You can overwrite the names of the headers in the configuration by setting the values of the following arguments (shown with their default values):
-
executionExceptionTypeHeaderName
("Execution-Exception-Type"
) -
executionExceptionMessageHeaderName
("Execution-Exception-Message"
) -
rootCauseExceptionTypeHeaderName
("Root-Cause-Exception-Type"
) -
rootCauseExceptionMessageHeaderName
("Root-Cause-Exception-Message"
)
For more information on circuit breakers and the gateway see the Spring Cloud CircuitBreaker Factory section.
6.7. The MapRequestHeader
GatewayFilter
Factory
The MapRequestHeader
GatewayFilter
factory takes fromHeader
and toHeader
parameters.
It creates a new named header (toHeader
), and the value is extracted out of an existing named header (fromHeader
) from the incoming http request.
If the input header does not exist, the filter has no impact.
If the new named header already exists, its values are augmented with the new values.
The following example configures a MapRequestHeader
:
spring:
cloud:
gateway:
routes:
- id: map_request_header_route
uri: https://example.org
filters:
- MapRequestHeader=Blue, X-Request-Red
This adds X-Request-Red:<values>
header to the downstream request with updated values from the incoming HTTP request’s Blue
header.
6.8. The PrefixPath
GatewayFilter
Factory
The PrefixPath
GatewayFilter
factory takes a single prefix
parameter.
The following example configures a PrefixPath
GatewayFilter
:
spring:
cloud:
gateway:
routes:
- id: prefixpath_route
uri: https://example.org
filters:
- PrefixPath=/mypath
This will prefix /mypath
to the path of all matching requests.
So a request to /hello
would be sent to /mypath/hello
.
6.9. The PreserveHostHeader
GatewayFilter
Factory
The PreserveHostHeader
GatewayFilter
factory has no parameters.
This filter sets a request attribute that the routing filter inspects to determine if the original host header should be sent, rather than the host header determined by the HTTP client.
The following example configures a PreserveHostHeader
GatewayFilter
:
spring:
cloud:
gateway:
routes:
- id: preserve_host_route
uri: https://example.org
filters:
- PreserveHostHeader
6.10. The RequestRateLimiter
GatewayFilter
Factory
The RequestRateLimiter
GatewayFilter
factory uses a RateLimiter
implementation to determine if the current request is allowed to proceed. If it is not, a status of HTTP 429 - Too Many Requests
(by default) is returned.
This filter takes an optional keyResolver
parameter and parameters specific to the rate limiter (described later in this section).
keyResolver
is a bean that implements the KeyResolver
interface.
In configuration, reference the bean by name using SpEL.
#{@myKeyResolver}
is a SpEL expression that references a bean named myKeyResolver
.
The following listing shows the KeyResolver
interface:
public interface KeyResolver {
Mono<String> resolve(ServerWebExchange exchange);
}
The KeyResolver
interface lets pluggable strategies derive the key for limiting requests.
In future milestone releases, there will be some KeyResolver
implementations.
The default implementation of KeyResolver
is the PrincipalNameKeyResolver
, which retrieves the Principal
from the ServerWebExchange
and calls Principal.getName()
.
By default, if the KeyResolver
does not find a key, requests are denied.
You can adjust this behavior by setting the spring.cloud.gateway.filter.request-rate-limiter.deny-empty-key
(true
or false
) and spring.cloud.gateway.filter.request-rate-limiter.empty-key-status-code
properties.
The Example 31. application.properties
# INVALID SHORTCUT CONFIGURATION spring.cloud.gateway.routes[0].filters[0]=RequestRateLimiter=2, 2, #{@userkeyresolver} |
6.10.1. The Redis RateLimiter
The Redis implementation is based off of work done at Stripe.
It requires the use of the spring-boot-starter-data-redis-reactive
Spring Boot starter.
The algorithm used is the Token Bucket Algorithm.
The redis-rate-limiter.replenishRate
property is how many requests per second you want a user to be allowed to do, without any dropped requests.
This is the rate at which the token bucket is filled.
The redis-rate-limiter.burstCapacity
property is the maximum number of requests a user is allowed to do in a single second.
This is the number of tokens the token bucket can hold.
Setting this value to zero blocks all requests.
The redis-rate-limiter.requestedTokens
property is how many tokens a request costs.
This is the number of tokens taken from the bucket for each request and defaults to 1
.
A steady rate is accomplished by setting the same value in replenishRate
and burstCapacity
.
Temporary bursts can be allowed by setting burstCapacity
higher than replenishRate
.
In this case, the rate limiter needs to be allowed some time between bursts (according to replenishRate
), as two consecutive bursts will result in dropped requests (HTTP 429 - Too Many Requests
).
The following listing configures a redis-rate-limiter
:
Rate limits bellow 1 request/s
are accomplished by setting replenishRate
to the wanted number of requests, requestedTokens
to the timespan in seconds and burstCapacity
to the product of replenishRate
and requestedTokens
, e.g. setting replenishRate=1
, requestedTokens=60
and burstCapacity=60
will result in a limit of 1 request/min
.
spring:
cloud:
gateway:
routes:
- id: requestratelimiter_route
uri: https://example.org
filters:
- name: RequestRateLimiter
args:
redis-rate-limiter.replenishRate: 10
redis-rate-limiter.burstCapacity: 20
redis-rate-limiter.requestedTokens: 1
The following example configures a KeyResolver in Java:
@Bean
KeyResolver userKeyResolver() {
return exchange -> Mono.just(exchange.getRequest().getQueryParams().getFirst("user"));
}
This defines a request rate limit of 10 per user. A burst of 20 is allowed, but, in the next second, only 10 requests are available.
The KeyResolver
is a simple one that gets the user
request parameter (note that this is not recommended for production).
You can also define a rate limiter as a bean that implements the RateLimiter
interface.
In configuration, you can reference the bean by name using SpEL.
#{@myRateLimiter}
is a SpEL expression that references a bean with named myRateLimiter
.
The following listing defines a rate limiter that uses the KeyResolver
defined in the previous listing:
spring:
cloud:
gateway:
routes:
- id: requestratelimiter_route
uri: https://example.org
filters:
- name: RequestRateLimiter
args:
rate-limiter: "#{@myRateLimiter}"
key-resolver: "#{@userKeyResolver}"
6.11. The RedirectTo
GatewayFilter
Factory
The RedirectTo
GatewayFilter
factory takes two parameters, status
and url
.
The status
parameter should be a 300 series redirect HTTP code, such as 301.
The url
parameter should be a valid URL.
This is the value of the Location
header.
For relative redirects, you should use uri: no://op
as the uri of your route definition.
The following listing configures a RedirectTo
GatewayFilter
:
spring:
cloud:
gateway:
routes:
- id: prefixpath_route
uri: https://example.org
filters:
- RedirectTo=302, https://acme.org
This will send a status 302 with a Location:https://acme.org
header to perform a redirect.
6.12. The RemoveRequestHeader
GatewayFilter Factory
The RemoveRequestHeader
GatewayFilter
factory takes a name
parameter.
It is the name of the header to be removed.
The following listing configures a RemoveRequestHeader
GatewayFilter
:
spring:
cloud:
gateway:
routes:
- id: removerequestheader_route
uri: https://example.org
filters:
- RemoveRequestHeader=X-Request-Foo
This removes the X-Request-Foo
header before it is sent downstream.
6.13. RemoveResponseHeader
GatewayFilter
Factory
The RemoveResponseHeader
GatewayFilter
factory takes a name
parameter.
It is the name of the header to be removed.
The following listing configures a RemoveResponseHeader
GatewayFilter
:
spring:
cloud:
gateway:
routes:
- id: removeresponseheader_route
uri: https://example.org
filters:
- RemoveResponseHeader=X-Response-Foo
This will remove the X-Response-Foo
header from the response before it is returned to the gateway client.
To remove any kind of sensitive header, you should configure this filter for any routes for which you may want to do so.
In addition, you can configure this filter once by using spring.cloud.gateway.default-filters
and have it applied to all routes.
6.14. The RemoveRequestParameter
GatewayFilter
Factory
The RemoveRequestParameter
GatewayFilter
factory takes a name
parameter.
It is the name of the query parameter to be removed.
The following example configures a RemoveRequestParameter
GatewayFilter
:
spring:
cloud:
gateway:
routes:
- id: removerequestparameter_route
uri: https://example.org
filters:
- RemoveRequestParameter=red
This will remove the red
parameter before it is sent downstream.
6.15. The RewritePath
GatewayFilter
Factory
The RewritePath
GatewayFilter
factory takes a path regexp
parameter and a replacement
parameter.
This uses Java regular expressions for a flexible way to rewrite the request path.
The following listing configures a RewritePath
GatewayFilter
:
spring:
cloud:
gateway:
routes:
- id: rewritepath_route
uri: https://example.org
predicates:
- Path=/red/**
filters:
- RewritePath=/red/?(?<segment>.*), /$\{segment}
For a request path of /red/blue
, this sets the path to /blue
before making the downstream request. Note that the $
should be replaced with $\
because of the YAML specification.
6.16. RewriteLocationResponseHeader
GatewayFilter
Factory
The RewriteLocationResponseHeader
GatewayFilter
factory modifies the value of the Location
response header, usually to get rid of backend-specific details.
It takes stripVersionMode
, locationHeaderName
, hostValue
, and protocolsRegex
parameters.
The following listing configures a RewriteLocationResponseHeader
GatewayFilter
:
spring:
cloud:
gateway:
routes:
- id: rewritelocationresponseheader_route
uri: http://example.org
filters:
- RewriteLocationResponseHeader=AS_IN_REQUEST, Location, ,
For example, for a request of POST api.example.com/some/object/name
, the Location
response header value of object-service.prod.example.net/v2/some/object/id
is rewritten as api.example.com/some/object/id
.
The stripVersionMode
parameter has the following possible values: NEVER_STRIP
, AS_IN_REQUEST
(default), and ALWAYS_STRIP
.
-
NEVER_STRIP
: The version is not stripped, even if the original request path contains no version. -
AS_IN_REQUEST
The version is stripped only if the original request path contains no version. -
ALWAYS_STRIP
The version is always stripped, even if the original request path contains version.
The hostValue
parameter, if provided, is used to replace the host:port
portion of the response Location
header.
If it is not provided, the value of the Host
request header is used.
The protocolsRegex
parameter must be a valid regex String
, against which the protocol name is matched.
If it is not matched, the filter does nothing.
The default is http|https|ftp|ftps
.
6.17. The RewriteResponseHeader
GatewayFilter
Factory
The RewriteResponseHeader
GatewayFilter
factory takes name
, regexp
, and replacement
parameters.
It uses Java regular expressions for a flexible way to rewrite the response header value.
The following example configures a RewriteResponseHeader
GatewayFilter
:
spring:
cloud:
gateway:
routes:
- id: rewriteresponseheader_route
uri: https://example.org
filters:
- RewriteResponseHeader=X-Response-Red, , password=[^&]+, password=***
For a header value of /42?user=ford&password=omg!what&flag=true
, it is set to /42?user=ford&password=***&flag=true
after making the downstream request.
You must use $\
to mean $
because of the YAML specification.
6.18. The SaveSession
GatewayFilter
Factory
The SaveSession
GatewayFilter
factory forces a WebSession::save
operation before forwarding the call downstream.
This is of particular use when using something like Spring Session with a lazy data store and you need to ensure the session state has been saved before making the forwarded call.
The following example configures a SaveSession
GatewayFilter
:
spring:
cloud:
gateway:
routes:
- id: save_session
uri: https://example.org
predicates:
- Path=/foo/**
filters:
- SaveSession
If you integrate Spring Security with Spring Session and want to ensure security details have been forwarded to the remote process, this is critical.
6.19. The SecureHeaders
GatewayFilter
Factory
The SecureHeaders
GatewayFilter
factory adds a number of headers to the response, per the recommendation made in this blog post.
The following headers (shown with their default values) are added:
-
X-Xss-Protection:1 (mode=block
) -
Strict-Transport-Security (max-age=631138519
) -
X-Frame-Options (DENY)
-
X-Content-Type-Options (nosniff)
-
Referrer-Policy (no-referrer)
-
Content-Security-Policy (default-src 'self' https:; font-src 'self' https: data:; img-src 'self' https: data:; object-src 'none'; script-src https:; style-src 'self' https: 'unsafe-inline)'
-
X-Download-Options (noopen)
-
X-Permitted-Cross-Domain-Policies (none)
To change the default values, set the appropriate property in the spring.cloud.gateway.filter.secure-headers
namespace.
The following properties are available:
-
xss-protection-header
-
strict-transport-security
-
x-frame-options
-
x-content-type-options
-
referrer-policy
-
content-security-policy
-
x-download-options
-
x-permitted-cross-domain-policies
To disable the default values set the spring.cloud.gateway.filter.secure-headers.disable
property with comma-separated values.
The following example shows how to do so:
spring.cloud.gateway.filter.secure-headers.disable=x-frame-options,strict-transport-security
The lowercase full name of the secure header needs to be used to disable it.. |
6.20. The SetPath
GatewayFilter
Factory
The SetPath
GatewayFilter
factory takes a path template
parameter.
It offers a simple way to manipulate the request path by allowing templated segments of the path.
This uses the URI templates from Spring Framework.
Multiple matching segments are allowed.
The following example configures a SetPath
GatewayFilter
:
spring:
cloud:
gateway:
routes:
- id: setpath_route
uri: https://example.org
predicates:
- Path=/red/{segment}
filters:
- SetPath=/{segment}
For a request path of /red/blue
, this sets the path to /blue
before making the downstream request.
6.21. The SetRequestHeader
GatewayFilter
Factory
The SetRequestHeader
GatewayFilter
factory takes name
and value
parameters.
The following listing configures a SetRequestHeader
GatewayFilter
:
spring:
cloud:
gateway:
routes:
- id: setrequestheader_route
uri: https://example.org
filters:
- SetRequestHeader=X-Request-Red, Blue
This GatewayFilter
replaces (rather than adding) all headers with the given name.
So, if the downstream server responded with a X-Request-Red:1234
, this would be replaced with X-Request-Red:Blue
, which is what the downstream service would receive.
SetRequestHeader
is aware of URI variables used to match a path or host.
URI variables may be used in the value and are expanded at runtime.
The following example configures an SetRequestHeader
GatewayFilter
that uses a variable:
spring:
cloud:
gateway:
routes:
- id: setrequestheader_route
uri: https://example.org
predicates:
- Host: {segment}.myhost.org
filters:
- SetRequestHeader=foo, bar-{segment}
6.22. The SetResponseHeader
GatewayFilter
Factory
The SetResponseHeader
GatewayFilter
factory takes name
and value
parameters.
The following listing configures a SetResponseHeader
GatewayFilter
:
spring:
cloud:
gateway:
routes:
- id: setresponseheader_route
uri: https://example.org
filters:
- SetResponseHeader=X-Response-Red, Blue
This GatewayFilter replaces (rather than adding) all headers with the given name.
So, if the downstream server responded with a X-Response-Red:1234
, this is replaced with X-Response-Red:Blue
, which is what the gateway client would receive.
SetResponseHeader
is aware of URI variables used to match a path or host.
URI variables may be used in the value and will be expanded at runtime.
The following example configures an SetResponseHeader
GatewayFilter
that uses a variable:
spring:
cloud:
gateway:
routes:
- id: setresponseheader_route
uri: https://example.org
predicates:
- Host: {segment}.myhost.org
filters:
- SetResponseHeader=foo, bar-{segment}
6.23. The SetStatus
GatewayFilter
Factory
The SetStatus
GatewayFilter
factory takes a single parameter, status
.
It must be a valid Spring HttpStatus
.
It may be the integer value 404
or the string representation of the enumeration: NOT_FOUND
.
The following listing configures a SetStatus
GatewayFilter
:
spring:
cloud:
gateway:
routes:
- id: setstatusstring_route
uri: https://example.org
filters:
- SetStatus=BAD_REQUEST
- id: setstatusint_route
uri: https://example.org
filters:
- SetStatus=401
In either case, the HTTP status of the response is set to 401.
You can configure the SetStatus
GatewayFilter
to return the original HTTP status code from the proxied request in a header in the response.
The header is added to the response if configured with the following property:
spring:
cloud:
gateway:
set-status:
original-status-header-name: original-http-status
6.24. The StripPrefix
GatewayFilter
Factory
The StripPrefix
GatewayFilter
factory takes one parameter, parts
.
The parts
parameter indicates the number of parts in the path to strip from the request before sending it downstream.
The following listing configures a StripPrefix
GatewayFilter
:
spring:
cloud:
gateway:
routes:
- id: nameRoot
uri: https://nameservice
predicates:
- Path=/name/**
filters:
- StripPrefix=2
When a request is made through the gateway to /name/blue/red
, the request made to nameservice
looks like nameservice/red
.
6.25. The Retry GatewayFilter
Factory
The Retry
GatewayFilter
factory supports the following parameters:
-
retries
: The number of retries that should be attempted. -
statuses
: The HTTP status codes that should be retried, represented by usingorg.springframework.http.HttpStatus
. -
methods
: The HTTP methods that should be retried, represented by usingorg.springframework.http.HttpMethod
. -
series
: The series of status codes to be retried, represented by usingorg.springframework.http.HttpStatus.Series
. -
exceptions
: A list of thrown exceptions that should be retried. -
backoff
: The configured exponential backoff for the retries. Retries are performed after a backoff interval offirstBackoff * (factor ^ n)
, wheren
is the iteration. IfmaxBackoff
is configured, the maximum backoff applied is limited tomaxBackoff
. IfbasedOnPreviousValue
is true, the backoff is calculated byusingprevBackoff * factor
.
The following defaults are configured for Retry
filter, if enabled:
-
retries
: Three times -
series
: 5XX series -
methods
: GET method -
exceptions
:IOException
andTimeoutException
-
backoff
: disabled
The following listing configures a Retry GatewayFilter
:
spring:
cloud:
gateway:
routes:
- id: retry_test
uri: http://localhost:8080/flakey
predicates:
- Host=*.retry.com
filters:
- name: Retry
args:
retries: 3
statuses: BAD_GATEWAY
methods: GET,POST
backoff:
firstBackoff: 10ms
maxBackoff: 50ms
factor: 2
basedOnPreviousValue: false
When using the retry filter with a forward: prefixed URL, the target endpoint should be written carefully so that, in case of an error, it does not do anything that could result in a response being sent to the client and committed.
For example, if the target endpoint is an annotated controller, the target controller method should not return ResponseEntity with an error status code.
Instead, it should throw an Exception or signal an error (for example, through a Mono.error(ex) return value), which the retry filter can be configured to handle by retrying.
|
When using the retry filter with any HTTP method with a body, the body will be cached and the gateway will become memory constrained. The body is cached in a request attribute defined by ServerWebExchangeUtils.CACHED_REQUEST_BODY_ATTR . The type of the object is a org.springframework.core.io.buffer.DataBuffer .
|
A simplified "shortcut" notation can be added with a single status
and method
.
The following two examples are equivalent:
spring:
cloud:
gateway:
routes:
- id: retry_route
uri: https://example.org
filters:
- name: Retry
args:
retries: 3
statuses: INTERNAL_SERVER_ERROR
methods: GET
backoff:
firstBackoff: 10ms
maxBackoff: 50ms
factor: 2
basedOnPreviousValue: false
- id: retryshortcut_route
uri: https://example.org
filters:
- Retry=3,INTERNAL_SERVER_ERROR,GET,10ms,50ms,2,false
6.26. The RequestSize
GatewayFilter
Factory
When the request size is greater than the permissible limit, the RequestSize
GatewayFilter
factory can restrict a request from reaching the downstream service.
The filter takes a maxSize
parameter.
The maxSize is a `DataSize
type, so values can be defined as a number followed by an optional DataUnit
suffix such as 'KB' or 'MB'. The default is 'B' for bytes.
It is the permissible size limit of the request defined in bytes.
The following listing configures a RequestSize
GatewayFilter
:
spring:
cloud:
gateway:
routes:
- id: request_size_route
uri: http://localhost:8080/upload
predicates:
- Path=/upload
filters:
- name: RequestSize
args:
maxSize: 5000000
The RequestSize
GatewayFilter
factory sets the response status as 413 Payload Too Large
with an additional header errorMessage
when the request is rejected due to size. The following example shows such an errorMessage
:
errorMessage` : `Request size is larger than permissible limit. Request size is 6.0 MB where permissible limit is 5.0 MB
The default request size is set to five MB if not provided as a filter argument in the route definition. |
6.27. The SetRequestHostHeader
GatewayFilter
Factory
There are certain situation when the host header may need to be overridden. In this situation, the SetRequestHostHeader
GatewayFilter
factory can replace the existing host header with a specified vaue.
The filter takes a host
parameter.
The following listing configures a SetRequestHostHeader
GatewayFilter
:
spring:
cloud:
gateway:
routes:
- id: set_request_host_header_route
uri: http://localhost:8080/headers
predicates:
- Path=/headers
filters:
- name: SetRequestHostHeader
args:
host: example.org
The SetRequestHostHeader
GatewayFilter
factory replaces the value of the host header with example.org
.
6.28. Modify a Request Body GatewayFilter
Factory
You can use the ModifyRequestBody
filter filter to modify the request body before it is sent downstream by the gateway.
This filter can be configured only by using the Java DSL. |
The following listing shows how to modify a request body GatewayFilter
:
@Bean
public RouteLocator routes(RouteLocatorBuilder builder) {
return builder.routes()
.route("rewrite_request_obj", r -> r.host("*.rewriterequestobj.org")
.filters(f -> f.prefixPath("/httpbin")
.modifyRequestBody(String.class, Hello.class, MediaType.APPLICATION_JSON_VALUE,
(exchange, s) -> return Mono.just(new Hello(s.toUpperCase())))).uri(uri))
.build();
}
static class Hello {
String message;
public Hello() { }
public Hello(String message) {
this.message = message;
}
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
}
}
if the request has no body, the RewriteFilter will be passed null . Mono.empty() should be returned to assign a missing body in the request.
|
6.29. Modify a Response Body GatewayFilter
Factory
You can use the ModifyResponseBody
filter to modify the response body before it is sent back to the client.
This filter can be configured only by using the Java DSL. |
The following listing shows how to modify a response body GatewayFilter
:
@Bean
public RouteLocator routes(RouteLocatorBuilder builder) {
return builder.routes()
.route("rewrite_response_upper", r -> r.host("*.rewriteresponseupper.org")
.filters(f -> f.prefixPath("/httpbin")
.modifyResponseBody(String.class, String.class,
(exchange, s) -> Mono.just(s.toUpperCase()))).uri(uri))
.build();
}
if the response has no body, the RewriteFilter will be passed null . Mono.empty() should be returned to assign a missing body in the response.
|
6.30. Token Relay GatewayFilter
Factory
A Token Relay is where an OAuth2 consumer acts as a Client and forwards the incoming token to outgoing resource requests. The consumer can be a pure Client (like an SSO application) or a Resource Server.
Spring Cloud Gateway can forward OAuth2 access tokens downstream to the services
it is proxying. To add this functionlity to gateway you need to add the
TokenRelayGatewayFilterFactory
like this:
@Bean
public RouteLocator customRouteLocator(RouteLocatorBuilder builder) {
return builder.routes()
.route("resource", r -> r.path("/resource")
.filters(f -> f.tokenRelay())
.uri("http://localhost:9000"))
.build();
}
or this
spring:
cloud:
gateway:
routes:
- id: resource
uri: http://localhost:9000
predicates:
- Path=/resource
filters:
- TokenRelay=
and it will (in addition to logging the user in and grabbing a token)
pass the authentication token downstream to the services (in this case
/resource
).
To enable this for Spring Cloud Gateway add the following dependencies
-
org.springframework.boot:spring-boot-starter-oauth2-client
How does it work? The {githubmaster}/src/main/java/org/springframework/cloud/gateway/security/TokenRelayGatewayFilterFactory.java[filter] extracts an access token from the currently authenticated user, and puts it in a request header for the downstream requests.
For a full working sample see this project.
A TokenRelayGatewayFilterFactory bean will only be created if the proper spring.security.oauth2.client.* properties are set which will trigger creation of a ReactiveClientRegistrationRepository bean.
|
The default implementation of ReactiveOAuth2AuthorizedClientService used by TokenRelayGatewayFilterFactory
uses an in-memory data store. You will need to provide your own implementation ReactiveOAuth2AuthorizedClientService
if you need a more robust solution.
|
6.31. Default Filters
To add a filter and apply it to all routes, you can use spring.cloud.gateway.default-filters
.
This property takes a list of filters.
The following listing defines a set of default filters:
spring:
cloud:
gateway:
default-filters:
- AddResponseHeader=X-Response-Default-Red, Default-Blue
- PrefixPath=/httpbin
7. Global Filters
The GlobalFilter
interface has the same signature as GatewayFilter
.
These are special filters that are conditionally applied to all routes.
This interface and its usage are subject to change in future milestone releases. |
7.1. Combined Global Filter and GatewayFilter
Ordering
When a request matches a route, the filtering web handler adds all instances of GlobalFilter
and all route-specific instances of GatewayFilter
to a filter chain.
This combined filter chain is sorted by the org.springframework.core.Ordered
interface, which you can set by implementing the getOrder()
method.
As Spring Cloud Gateway distinguishes between “pre” and “post” phases for filter logic execution (see How it Works), the filter with the highest precedence is the first in the “pre”-phase and the last in the “post”-phase.
The following listing configures a filter chain:
@Bean
public GlobalFilter customFilter() {
return new CustomGlobalFilter();
}
public class CustomGlobalFilter implements GlobalFilter, Ordered {
@Override
public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
log.info("custom global filter");
return chain.filter(exchange);
}
@Override
public int getOrder() {
return -1;
}
}
7.2. Forward Routing Filter
The ForwardRoutingFilter
looks for a URI in the exchange attribute ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR
.
If the URL has a forward
scheme (such as forward:///localendpoint
), it uses the Spring DispatcherHandler
to handle the request.
The path part of the request URL is overridden with the path in the forward URL.
The unmodified original URL is appended to the list in the ServerWebExchangeUtils.GATEWAY_ORIGINAL_REQUEST_URL_ATTR
attribute.
7.3. The ReactiveLoadBalancerClientFilter
The ReactiveLoadBalancerClientFilter
looks for a URI in the exchange attribute named ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR
.
If the URL has a lb
scheme (such as lb://myservice
), it uses the Spring Cloud ReactorLoadBalancer
to resolve the name (myservice
in this example) to an actual host and port and replaces the URI in the same attribute.
The unmodified original URL is appended to the list in the ServerWebExchangeUtils.GATEWAY_ORIGINAL_REQUEST_URL_ATTR
attribute.
The filter also looks in the ServerWebExchangeUtils.GATEWAY_SCHEME_PREFIX_ATTR
attribute to see if it equals lb
.
If so, the same rules apply.
The following listing configures a ReactiveLoadBalancerClientFilter
:
spring:
cloud:
gateway:
routes:
- id: myRoute
uri: lb://service
predicates:
- Path=/service/**
By default, when a service instance cannot be found by the ReactorLoadBalancer , a 503 is returned.
You can configure the gateway to return a 404 by setting spring.cloud.gateway.loadbalancer.use404=true .
|
The isSecure value of the ServiceInstance returned from the ReactiveLoadBalancerClientFilter overrides
the scheme specified in the request made to the Gateway.
For example, if the request comes into the Gateway over HTTPS but the ServiceInstance indicates it is not secure, the downstream request is made over HTTP .
The opposite situation can also apply.
However, if GATEWAY_SCHEME_PREFIX_ATTR is specified for the route in the Gateway configuration, the prefix is stripped and the resulting scheme from the route URL overrides the ServiceInstance configuration.
|
Gateway supports all the LoadBalancer features. You can read more about them in the Spring Cloud Commons documentation. |
7.4. The Netty Routing Filter
The Netty routing filter runs if the URL located in the ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR
exchange attribute has a http
or https
scheme.
It uses the Netty HttpClient
to make the downstream proxy request.
The response is put in the ServerWebExchangeUtils.CLIENT_RESPONSE_ATTR
exchange attribute for use in a later filter.
(There is also an experimental WebClientHttpRoutingFilter
that performs the same function but does not require Netty.)
7.5. The Netty Write Response Filter
The NettyWriteResponseFilter
runs if there is a Netty HttpClientResponse
in the ServerWebExchangeUtils.CLIENT_RESPONSE_ATTR
exchange attribute.
It runs after all other filters have completed and writes the proxy response back to the gateway client response.
(There is also an experimental WebClientWriteResponseFilter
that performs the same function but does not require Netty.)
7.6. The RouteToRequestUrl
Filter
If there is a Route
object in the ServerWebExchangeUtils.GATEWAY_ROUTE_ATTR
exchange attribute, the RouteToRequestUrlFilter
runs.
It creates a new URI, based off of the request URI but updated with the URI attribute of the Route
object.
The new URI is placed in the ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR
exchange attribute`.
If the URI has a scheme prefix, such as lb:ws://serviceid
, the lb
scheme is stripped from the URI and placed in the ServerWebExchangeUtils.GATEWAY_SCHEME_PREFIX_ATTR
for use later in the filter chain.
7.7. The Websocket Routing Filter
If the URL located in the ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR
exchange attribute has a ws
or wss
scheme, the websocket routing filter runs. It uses the Spring WebSocket infrastructure to forward the websocket request downstream.
You can load-balance websockets by prefixing the URI with lb
, such as lb:ws://serviceid
.
If you use SockJS as a fallback over normal HTTP, you should configure a normal HTTP route as well as the websocket Route. |
The following listing configures a websocket routing filter:
spring:
cloud:
gateway:
routes:
# SockJS route
- id: websocket_sockjs_route
uri: http://localhost:3001
predicates:
- Path=/websocket/info/**
# Normal Websocket route
- id: websocket_route
uri: ws://localhost:3001
predicates:
- Path=/websocket/**
7.8. The Gateway Metrics Filter
To enable gateway metrics, add spring-boot-starter-actuator as a project dependency. Then, by default, the gateway metrics filter runs as long as the property spring.cloud.gateway.metrics.enabled
is not set to false
. This filter adds a timer metric named spring.cloud.gateway.requests
with the following tags:
-
routeId
: The route ID. -
routeUri
: The URI to which the API is routed. -
outcome
: The outcome, as classified by HttpStatus.Series. -
status
: The HTTP status of the request returned to the client. -
httpStatusCode
: The HTTP Status of the request returned to the client. -
httpMethod
: The HTTP method used for the request.
In addition, through the property spring.cloud.gateway.metrics.tags.path.enabled
(by default, set to false), you can activate an extra metric with the tag:
-
path
: Path of the request.
These metrics are then available to be scraped from /actuator/metrics/spring.cloud.gateway.requests
and can be easily integrated with Prometheus to create a Grafana dashboard.
To enable the prometheus endpoint, add micrometer-registry-prometheus as a project dependency.
|
7.9. Marking An Exchange As Routed
After the gateway has routed a ServerWebExchange
, it marks that exchange as “routed” by adding gatewayAlreadyRouted
to the exchange attributes. Once a request has been marked as routed, other routing filters will not route the request again,
essentially skipping the filter. There are convenience methods that you can use to mark an exchange as routed
or check if an exchange has already been routed.
-
ServerWebExchangeUtils.isAlreadyRouted
takes aServerWebExchange
object and checks if it has been “routed”. -
ServerWebExchangeUtils.setAlreadyRouted
takes aServerWebExchange
object and marks it as “routed”.
8. HttpHeadersFilters
HttpHeadersFilters are applied to requests before sending them downstream, such as in the NettyRoutingFilter
.
8.1. Forwarded Headers Filter
The Forwarded
Headers Filter creates a Forwarded
header to send to the downstream service. It adds the Host
header, scheme and port of the current request to any existing Forwarded
header.
8.2. RemoveHopByHop Headers Filter
The RemoveHopByHop
Headers Filter removes headers from forwarded requests. The default list of headers that is removed comes from the IETF.
-
Connection
-
Keep-Alive
-
Proxy-Authenticate
-
Proxy-Authorization
-
TE
-
Trailer
-
Transfer-Encoding
-
Upgrade
To change this, set the spring.cloud.gateway.filter.remove-hop-by-hop.headers
property to the list of header names to remove.
8.3. XForwarded Headers Filter
The XForwarded
Headers Filter creates various a X-Forwarded-*
headers to send to the downstream service. It users the Host
header, scheme, port and path of the current request to create the various headers.
Creating of individual headers can be controlled by the following boolean properties (defaults to true):
-
spring.cloud.gateway.x-forwarded.for-enabled
-
spring.cloud.gateway.x-forwarded.host-enabled
-
spring.cloud.gateway.x-forwarded.port-enabled
-
spring.cloud.gateway.x-forwarded.proto-enabled
-
spring.cloud.gateway.x-forwarded.prefix-enabled
Appending multiple headers can be controlled by the following boolean properties (defaults to true):
-
spring.cloud.gateway.x-forwarded.for-append
-
spring.cloud.gateway.x-forwarded.host-append
-
spring.cloud.gateway.x-forwarded.port-append
-
spring.cloud.gateway.x-forwarded.proto-append
-
spring.cloud.gateway.x-forwarded.prefix-append
9. TLS and SSL
The gateway can listen for requests on HTTPS by following the usual Spring server configuration. The following example shows how to do so:
server:
ssl:
enabled: true
key-alias: scg
key-store-password: scg1234
key-store: classpath:scg-keystore.p12
key-store-type: PKCS12
You can route gateway routes to both HTTP and HTTPS backends. If you are routing to an HTTPS backend, you can configure the gateway to trust all downstream certificates with the following configuration:
spring:
cloud:
gateway:
httpclient:
ssl:
useInsecureTrustManager: true
Using an insecure trust manager is not suitable for production. For a production deployment, you can configure the gateway with a set of known certificates that it can trust with the following configuration:
spring:
cloud:
gateway:
httpclient:
ssl:
trustedX509Certificates:
- cert1.pem
- cert2.pem
If the Spring Cloud Gateway is not provisioned with trusted certificates, the default trust store is used (which you can override by setting the javax.net.ssl.trustStore
system property).
9.1. TLS Handshake
The gateway maintains a client pool that it uses to route to backends. When communicating over HTTPS, the client initiates a TLS handshake. A number of timeouts are associated with this handshake. You can configure these timeouts can be configured (defaults shown) as follows:
spring:
cloud:
gateway:
httpclient:
ssl:
handshake-timeout-millis: 10000
close-notify-flush-timeout-millis: 3000
close-notify-read-timeout-millis: 0
10. Configuration
Configuration for Spring Cloud Gateway is driven by a collection of RouteDefinitionLocator
instances.
The following listing shows the definition of the RouteDefinitionLocator
interface:
public interface RouteDefinitionLocator {
Flux<RouteDefinition> getRouteDefinitions();
}
By default, a PropertiesRouteDefinitionLocator
loads properties by using Spring Boot’s @ConfigurationProperties
mechanism.
The earlier configuration examples all use a shortcut notation that uses positional arguments rather than named ones. The following two examples are equivalent:
spring:
cloud:
gateway:
routes:
- id: setstatus_route
uri: https://example.org
filters:
- name: SetStatus
args:
status: 401
- id: setstatusshortcut_route
uri: https://example.org
filters:
- SetStatus=401
For some usages of the gateway, properties are adequate, but some production use cases benefit from loading configuration from an external source, such as a database. Future milestone versions will have RouteDefinitionLocator
implementations based off of Spring Data Repositories, such as Redis, MongoDB, and Cassandra.
10.1. RouteDefinition Metrics
To enable RouteDefinition
metrics, add spring-boot-starter-actuator as a project dependency. Then, by default, the metrics will be available as long as the property spring.cloud.gateway.metrics.enabled
is set to true
. A gauge metric named spring.cloud.gateway.routes.count
will be added, whose value is the number of RouteDefinitions
. This metric will be available from /actuator/metrics/spring.cloud.gateway.routes.count
.
11. Route Metadata Configuration
You can configure additional parameters for each route by using metadata, as follows:
spring:
cloud:
gateway:
routes:
- id: route_with_metadata
uri: https://example.org
metadata:
optionName: "OptionValue"
compositeObject:
name: "value"
iAmNumber: 1
You could acquire all metadata properties from an exchange, as follows:
Route route = exchange.getAttribute(GATEWAY_ROUTE_ATTR);
// get all metadata properties
route.getMetadata();
// get a single metadata property
route.getMetadata(someKey);
12. Http timeouts configuration
Http timeouts (response and connect) can be configured for all routes and overridden for each specific route.
12.1. Global timeouts
To configure Global http timeouts:
connect-timeout
must be specified in milliseconds.
response-timeout
must be specified as a java.time.Duration
spring:
cloud:
gateway:
httpclient:
connect-timeout: 1000
response-timeout: 5s
12.2. Per-route timeouts
To configure per-route timeouts:
connect-timeout
must be specified in milliseconds.
response-timeout
must be specified in milliseconds.
- id: per_route_timeouts
uri: https://example.org
predicates:
- name: Path
args:
pattern: /delay/{timeout}
metadata:
response-timeout: 200
connect-timeout: 200
import static org.springframework.cloud.gateway.support.RouteMetadataUtils.CONNECT_TIMEOUT_ATTR;
import static org.springframework.cloud.gateway.support.RouteMetadataUtils.RESPONSE_TIMEOUT_ATTR;
@Bean
public RouteLocator customRouteLocator(RouteLocatorBuilder routeBuilder){
return routeBuilder.routes()
.route("test1", r -> {
return r.host("*.somehost.org").and().path("/somepath")
.filters(f -> f.addRequestHeader("header1", "header-value-1"))
.uri("http://someuri")
.metadata(RESPONSE_TIMEOUT_ATTR, 200)
.metadata(CONNECT_TIMEOUT_ATTR, 200);
})
.build();
}
12.3. Fluent Java Routes API
To allow for simple configuration in Java, the RouteLocatorBuilder
bean includes a fluent API.
The following listing shows how it works:
// static imports from GatewayFilters and RoutePredicates
@Bean
public RouteLocator customRouteLocator(RouteLocatorBuilder builder, ThrottleGatewayFilterFactory throttle) {
return builder.routes()
.route(r -> r.host("**.abc.org").and().path("/image/png")
.filters(f ->
f.addResponseHeader("X-TestHeader", "foobar"))
.uri("http://httpbin.org:80")
)
.route(r -> r.path("/image/webp")
.filters(f ->
f.addResponseHeader("X-AnotherHeader", "baz"))
.uri("http://httpbin.org:80")
.metadata("key", "value")
)
.route(r -> r.order(-1)
.host("**.throttle.org").and().path("/get")
.filters(f -> f.filter(throttle.apply(1,
1,
10,
TimeUnit.SECONDS)))
.uri("http://httpbin.org:80")
.metadata("key", "value")
)
.build();
}
This style also allows for more custom predicate assertions.
The predicates defined by RouteDefinitionLocator
beans are combined using logical and
.
By using the fluent Java API, you can use the and()
, or()
, and negate()
operators on the Predicate
class.
12.4. The DiscoveryClient
Route Definition Locator
You can configure the gateway to create routes based on services registered with a DiscoveryClient
compatible service registry.
To enable this, set spring.cloud.gateway.discovery.locator.enabled=true
and make sure a DiscoveryClient
implementation (such as Netflix Eureka, Consul, or Zookeeper) is on the classpath and enabled.
12.4.1. Configuring Predicates and Filters For DiscoveryClient
Routes
By default, the gateway defines a single predicate and filter for routes created with a DiscoveryClient
.
The default predicate is a path predicate defined with the pattern /serviceId/**
, where serviceId
is
the ID of the service from the DiscoveryClient
.
The default filter is a rewrite path filter with the regex /serviceId/?(?<remaining>.*)
and the replacement /${remaining}
.
This strips the service ID from the path before the request is sent downstream.
If you want to customize the predicates or filters used by the DiscoveryClient
routes, set spring.cloud.gateway.discovery.locator.predicates[x]
and spring.cloud.gateway.discovery.locator.filters[y]
.
When doing so, you need to make sure to include the default predicate and filter shown earlier, if you want to retain that functionality.
The following example shows what this looks like:
spring.cloud.gateway.discovery.locator.predicates[0].name: Path spring.cloud.gateway.discovery.locator.predicates[0].args[pattern]: "'/'+serviceId+'/**'" spring.cloud.gateway.discovery.locator.predicates[1].name: Host spring.cloud.gateway.discovery.locator.predicates[1].args[pattern]: "'**.foo.com'" spring.cloud.gateway.discovery.locator.filters[0].name: CircuitBreaker spring.cloud.gateway.discovery.locator.filters[0].args[name]: serviceId spring.cloud.gateway.discovery.locator.filters[1].name: RewritePath spring.cloud.gateway.discovery.locator.filters[1].args[regexp]: "'/' + serviceId + '/?(?<remaining>.*)'" spring.cloud.gateway.discovery.locator.filters[1].args[replacement]: "'/${remaining}'"
13. Reactor Netty Access Logs
To enable Reactor Netty access logs, set -Dreactor.netty.http.server.accessLogEnabled=true
.
It must be a Java System Property, not a Spring Boot property. |
You can configure the logging system to have a separate access log file. The following example creates a Logback configuration:
<appender name="accessLog" class="ch.qos.logback.core.FileAppender">
<file>access_log.log</file>
<encoder>
<pattern>%msg%n</pattern>
</encoder>
</appender>
<appender name="async" class="ch.qos.logback.classic.AsyncAppender">
<appender-ref ref="accessLog" />
</appender>
<logger name="reactor.netty.http.server.AccessLog" level="INFO" additivity="false">
<appender-ref ref="async"/>
</logger>
14. CORS Configuration
You can configure the gateway to control CORS behavior. The “global” CORS configuration is a map of URL patterns to Spring Framework CorsConfiguration
.
The following example configures CORS:
spring:
cloud:
gateway:
globalcors:
cors-configurations:
'[/**]':
allowedOrigins: "https://docs.spring.io"
allowedMethods:
- GET
In the preceding example, CORS requests are allowed from requests that originate from docs.spring.io
for all GET requested paths.
To provide the same CORS configuration to requests that are not handled by some gateway route predicate, set the spring.cloud.gateway.globalcors.add-to-simple-url-handler-mapping
property to true
.
This is useful when you try to support CORS preflight requests and your route predicate does not evalute to true
because the HTTP method is options
.
15. Actuator API
The /gateway
actuator endpoint lets you monitor and interact with a Spring Cloud Gateway application.
To be remotely accessible, the endpoint has to be enabled and exposed over HTTP or JMX in the application properties.
The following listing shows how to do so:
management.endpoint.gateway.enabled=true # default value
management.endpoints.web.exposure.include=gateway
15.1. Verbose Actuator Format
A new, more verbose format has been added to Spring Cloud Gateway.
It adds more detail to each route, letting you view the predicates and filters associated with each route along with any configuration that is available.
The following example configures /actuator/gateway/routes
:
[
{
"predicate": "(Hosts: [**.addrequestheader.org] && Paths: [/headers], match trailing slash: true)",
"route_id": "add_request_header_test",
"filters": [
"[[AddResponseHeader X-Response-Default-Foo = 'Default-Bar'], order = 1]",
"[[AddRequestHeader X-Request-Foo = 'Bar'], order = 1]",
"[[PrefixPath prefix = '/httpbin'], order = 2]"
],
"uri": "lb://testservice",
"order": 0
}
]
This feature is enabled by default. To disable it, set the following property:
spring.cloud.gateway.actuator.verbose.enabled=false
This will default to true
in a future release.
15.2. Retrieving Route Filters
This section details how to retrieve route filters, including:
15.2.1. Global Filters
To retrieve the global filters applied to all routes, make a GET
request to /actuator/gateway/globalfilters
. The resulting response is similar to the following:
{ "org.springframework.cloud.gateway.filter.ReactiveLoadBalancerClientFilter@77856cc5": 10100, "org.springframework.cloud.gateway.filter.RouteToRequestUrlFilter@4f6fd101": 10000, "org.springframework.cloud.gateway.filter.NettyWriteResponseFilter@32d22650": -1, "org.springframework.cloud.gateway.filter.ForwardRoutingFilter@106459d9": 2147483647, "org.springframework.cloud.gateway.filter.NettyRoutingFilter@1fbd5e0": 2147483647, "org.springframework.cloud.gateway.filter.ForwardPathFilter@33a71d23": 0, "org.springframework.cloud.gateway.filter.AdaptCachedBodyGlobalFilter@135064ea": 2147483637, "org.springframework.cloud.gateway.filter.WebsocketRoutingFilter@23c05889": 2147483646 }
The response contains the details of the global filters that are in place.
For each global filter, there is a string representation of the filter object (for example, org.springframework.cloud.gateway.filter.ReactiveLoadBalancerClientFilter@77856cc5
) and the corresponding order in the filter chain.}
15.2.2. Route Filters
To retrieve the GatewayFilter
factories applied to routes, make a GET
request to /actuator/gateway/routefilters
.
The resulting response is similar to the following:
{ "[AddRequestHeaderGatewayFilterFactory@570ed9c configClass = AbstractNameValueGatewayFilterFactory.NameValueConfig]": null, "[SecureHeadersGatewayFilterFactory@fceab5d configClass = Object]": null, "[SaveSessionGatewayFilterFactory@4449b273 configClass = Object]": null }
The response contains the details of the GatewayFilter
factories applied to any particular route.
For each factory there is a string representation of the corresponding object (for example, [SecureHeadersGatewayFilterFactory@fceab5d configClass = Object]
).
Note that the null
value is due to an incomplete implementation of the endpoint controller, because it tries to set the order of the object in the filter chain, which does not apply to a GatewayFilter
factory object.
15.3. Refreshing the Route Cache
To clear the routes cache, make a POST
request to /actuator/gateway/refresh
.
The request returns a 200 without a response body.
15.4. Retrieving the Routes Defined in the Gateway
To retrieve the routes defined in the gateway, make a GET
request to /actuator/gateway/routes
.
The resulting response is similar to the following:
[{ "route_id": "first_route", "route_object": { "predicate": "org.springframework.cloud.gateway.handler.predicate.PathRoutePredicateFactory$$Lambda$432/1736826640@1e9d7e7d", "filters": [ "OrderedGatewayFilter{delegate=org.springframework.cloud.gateway.filter.factory.PreserveHostHeaderGatewayFilterFactory$$Lambda$436/674480275@6631ef72, order=0}" ] }, "order": 0 }, { "route_id": "second_route", "route_object": { "predicate": "org.springframework.cloud.gateway.handler.predicate.PathRoutePredicateFactory$$Lambda$432/1736826640@cd8d298", "filters": [] }, "order": 0 }]
The response contains the details of all the routes defined in the gateway. The following table describes the structure of each element (each is a route) of the response:
Path | Type | Description |
---|---|---|
|
String |
The route ID. |
|
Object |
The route predicate. |
|
Array |
The |
|
Number |
The route order. |
15.5. Retrieving Information about a Particular Route
To retrieve information about a single route, make a GET
request to /actuator/gateway/routes/{id}
(for example, /actuator/gateway/routes/first_route
).
The resulting response is similar to the following:
{ "id": "first_route", "predicates": [{ "name": "Path", "args": {"_genkey_0":"/first"} }], "filters": [], "uri": "https://www.uri-destination.org", "order": 0 }]
The following table describes the structure of the response:
Path | Type | Description |
---|---|---|
|
String |
The route ID. |
|
Array |
The collection of route predicates. Each item defines the name and the arguments of a given predicate. |
|
Array |
The collection of filters applied to the route. |
|
String |
The destination URI of the route. |
|
Number |
The route order. |
15.6. Creating and Deleting a Particular Route
To create a route, make a POST
request to /gateway/routes/{id_route_to_create}
with a JSON body that specifies the fields of the route (see Retrieving Information about a Particular Route).
To delete a route, make a DELETE
request to /gateway/routes/{id_route_to_delete}
.
15.7. Recap: The List of All endpoints
The folloiwng table below summarizes the Spring Cloud Gateway actuator endpoints (note that each endpoint has /actuator/gateway
as the base-path):
ID | HTTP Method | Description |
---|---|---|
|
GET |
Displays the list of global filters applied to the routes. |
|
GET |
Displays the list of |
|
POST |
Clears the routes cache. |
|
GET |
Displays the list of routes defined in the gateway. |
|
GET |
Displays information about a particular route. |
|
POST |
Adds a new route to the gateway. |
|
DELETE |
Removes an existing route from the gateway. |
16. Troubleshooting
This section covers common problems that may arise when you use Spring Cloud Gateway.
16.1. Log Levels
The following loggers may contain valuable troubleshooting information at the DEBUG
and TRACE
levels:
-
org.springframework.cloud.gateway
-
org.springframework.http.server.reactive
-
org.springframework.web.reactive
-
org.springframework.boot.autoconfigure.web
-
reactor.netty
-
redisratelimiter
16.2. Wiretap
The Reactor Netty HttpClient
and HttpServer
can have wiretap enabled.
When combined with setting the reactor.netty
log level to DEBUG
or TRACE
, it enables the logging of information, such as headers and bodies sent and received across the wire.
To enable wiretap, set spring.cloud.gateway.httpserver.wiretap=true
or spring.cloud.gateway.httpclient.wiretap=true
for the HttpServer
and HttpClient
, respectively.
17. Developer Guide
These are basic guides to writing some custom components of the gateway.
17.1. Writing Custom Route Predicate Factories
In order to write a Route Predicate you will need to implement RoutePredicateFactory
. There is an abstract class called AbstractRoutePredicateFactory
which you can extend.
public class MyRoutePredicateFactory extends AbstractRoutePredicateFactory<HeaderRoutePredicateFactory.Config> {
public MyRoutePredicateFactory() {
super(Config.class);
}
@Override
public Predicate<ServerWebExchange> apply(Config config) {
// grab configuration from Config object
return exchange -> {
//grab the request
ServerHttpRequest request = exchange.getRequest();
//take information from the request to see if it
//matches configuration.
return matches(config, request);
};
}
public static class Config {
//Put the configuration properties for your filter here
}
}
17.2. Writing Custom GatewayFilter Factories
To write a GatewayFilter
, you must implement GatewayFilterFactory
.
You can extend an abstract class called AbstractGatewayFilterFactory
.
The following examples show how to do so:
public class PreGatewayFilterFactory extends AbstractGatewayFilterFactory<PreGatewayFilterFactory.Config> {
public PreGatewayFilterFactory() {
super(Config.class);
}
@Override
public GatewayFilter apply(Config config) {
// grab configuration from Config object
return (exchange, chain) -> {
//If you want to build a "pre" filter you need to manipulate the
//request before calling chain.filter
ServerHttpRequest.Builder builder = exchange.getRequest().mutate();
//use builder to manipulate the request
return chain.filter(exchange.mutate().request(builder.build()).build());
};
}
public static class Config {
//Put the configuration properties for your filter here
}
}
public class PostGatewayFilterFactory extends AbstractGatewayFilterFactory<PostGatewayFilterFactory.Config> {
public PostGatewayFilterFactory() {
super(Config.class);
}
@Override
public GatewayFilter apply(Config config) {
// grab configuration from Config object
return (exchange, chain) -> {
return chain.filter(exchange).then(Mono.fromRunnable(() -> {
ServerHttpResponse response = exchange.getResponse();
//Manipulate the response in some way
}));
};
}
public static class Config {
//Put the configuration properties for your filter here
}
}
17.2.1. Naming Custom Filters And References In Configuration
Custom filters class names should end in GatewayFilterFactory
.
For example, to reference a filter named Something
in configuration files, the filter
must be in a class named SomethingGatewayFilterFactory
.
It is possible to create a gateway filter named without the
GatewayFilterFactory suffix, such as class AnotherThing . This filter could be
referenced as AnotherThing in configuration files. This is not a supported naming
convention and this syntax may be removed in future releases. Please update the filter
name to be compliant.
|
17.3. Writing Custom Global Filters
To write a custom global filter, you must implement GlobalFilter
interface.
This applies the filter to all requests.
The following examples show how to set up global pre and post filters, respectively:
@Bean
public GlobalFilter customGlobalFilter() {
return (exchange, chain) -> exchange.getPrincipal()
.map(Principal::getName)
.defaultIfEmpty("Default User")
.map(userName -> {
//adds header to proxied request
exchange.getRequest().mutate().header("CUSTOM-REQUEST-HEADER", userName).build();
return exchange;
})
.flatMap(chain::filter);
}
@Bean
public GlobalFilter customGlobalPostFilter() {
return (exchange, chain) -> chain.filter(exchange)
.then(Mono.just(exchange))
.map(serverWebExchange -> {
//adds header to response
serverWebExchange.getResponse().getHeaders().set("CUSTOM-RESPONSE-HEADER",
HttpStatus.OK.equals(serverWebExchange.getResponse().getStatusCode()) ? "It worked": "It did not work");
return serverWebExchange;
})
.then();
}
18. Building a Simple Gateway by Using Spring MVC or Webflux
The following describes an alternative style gateway. None of the prior documentation applies to what follows. |
Spring Cloud Gateway provides a utility object called ProxyExchange
.
You can use it inside a regular Spring web handler as a method parameter.
It supports basic downstream HTTP exchanges through methods that mirror the HTTP verbs.
With MVC, it also supports forwarding to a local handler through the forward()
method.
To use the ProxyExchange
, include the right module in your classpath (either spring-cloud-gateway-mvc
or spring-cloud-gateway-webflux
).
The following MVC example proxies a request to /test
downstream to a remote server:
@RestController
@SpringBootApplication
public class GatewaySampleApplication {
@Value("${remote.home}")
private URI home;
@GetMapping("/test")
public ResponseEntity<?> proxy(ProxyExchange<byte[]> proxy) throws Exception {
return proxy.uri(home.toString() + "/image/png").get();
}
}
The following example does the same thing with Webflux:
@RestController
@SpringBootApplication
public class GatewaySampleApplication {
@Value("${remote.home}")
private URI home;
@GetMapping("/test")
public Mono<ResponseEntity<?>> proxy(ProxyExchange<byte[]> proxy) throws Exception {
return proxy.uri(home.toString() + "/image/png").get();
}
}
Convenience methods on the ProxyExchange
enable the handler method to discover and enhance the URI path of the incoming request.
For example, you might want to extract the trailing elements of a path to pass them downstream:
@GetMapping("/proxy/path/**")
public ResponseEntity<?> proxyPath(ProxyExchange<byte[]> proxy) throws Exception {
String path = proxy.path("/proxy/path/");
return proxy.uri(home.toString() + "/foos/" + path).get();
}
All the features of Spring MVC and Webflux are available to gateway handler methods.
As a result, you can inject request headers and query parameters, for instance, and you can constrain the incoming requests with declarations in the mapping annotation.
See the documentation for @RequestMapping
in Spring MVC for more details of those features.
You can add headers to the downstream response by using the header()
methods on ProxyExchange
.
You can also manipulate response headers (and anything else you like in the response) by adding a mapper to the get()
method (and other methods).
The mapper is a Function
that takes the incoming ResponseEntity
and converts it to an outgoing one.
First-class support is provided for “sensitive” headers (by default, cookie
and authorization
), which are not passed downstream, and for “proxy” (x-forwarded-*
) headers.
19. Configuration properties
To see the list of all Spring Cloud Gateway related configuration properties, see the appendix.