Spring Integration provides an http namespace and the corresponding schema definition. To include it in your configuration, simply provide the following namespace declaration in your application context configuration file:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:int="http://www.springframework.org/schema/integration"
  xmlns:int-http="http://www.springframework.org/schema/integration/http"
  xsi:schemaLocation="
    http://www.springframework.org/schema/beans
    https://www.springframework.org/schema/beans/spring-beans.xsd
    http://www.springframework.org/schema/integration
    https://www.springframework.org/schema/integration/spring-integration.xsd
    http://www.springframework.org/schema/integration/http
    https://www.springframework.org/schema/integration/http/spring-integration-http.xsd">
    ...
</beans>

The XML Namespace provides two components for handling HTTP Inbound requests. In order to process requests without returning a dedicated response, use the inbound-channel-adapter:

<int-http:inbound-channel-adapter id="httpChannelAdapter" channel="requests"
    supported-methods="PUT, DELETE"/>

To process requests that do expect a response, use an inbound-gateway:

<int-http:inbound-gateway id="inboundGateway"
    request-channel="requests"
    reply-channel="responses"/>

	Note
	Spring Integration 3.0 is improving the REST support by introducing the IntegrationRequestMappingHandlerMapping. The implementation relies on the enhanced REST support provided by Spring Framework 3.1 or higher.

The parsing of the HTTP Inbound Gateway or the HTTP Inbound Channel Adapter registers an integrationRequestMappingHandlerMapping bean of type IntegrationRequestMappingHandlerMapping, in case there is none registered, yet. This particular implementation of the HandlerMapping delegates its logic to the RequestMappingInfoHandlerMapping. The implementation provides similar functionality as the one provided by the org.springframework.web.bind.annotation.RequestMapping annotation in Spring MVC.

	Note
	For more information, please see Mapping Requests With @RequestMapping.

For this purpose, Spring Integration 3.0 introduces the <request-mapping> sub-element. This optional sub-element can be added to the <http:inbound-channel-adapter> and the <http:inbound-gateway>. It works in conjunction with the path and supported-methods attributes:

<inbound-gateway id="inboundController"
    request-channel="requests"
    reply-channel="responses"
    path="/foo/{fooId}"
    supported-methods="GET"
    view-name="foo"
    error-code="oops">
   <request-mapping headers="User-Agent"
     params="myParam=myValue"
     consumes="application/json"
     produces="!text/plain"/>
</inbound-gateway>

Based on this configuration, the namespace parser creates an instance of the IntegrationRequestMappingHandlerMapping (if none exists, yet), a HttpRequestHandlingController bean and associated with it an instance of RequestMapping, which in turn, is converted to the Spring MVC RequestMappingInfo.

The <request-mapping> sub-element provides the following attributes:

With the path and supported-methods attributes of the <http:inbound-channel-adapter> or the <http:inbound-gateway>, <request-mapping> attributes translate directly into the respective options provided by the org.springframework.web.bind.annotation.RequestMapping annotation in Spring MVC.

The <request-mapping> sub-element allows you to configure several Spring Integration HTTP Inbound Endpoints to the same path (or even the same supported-methods) and to provide different downstream message flows based on incoming HTTP requests.

Alternatively, you can also declare just one HTTP Inbound Endpoint and apply routing and filtering logic within the Spring Integration flow to achieve the same result. This allows you to get the Message into the flow as early as possibly, e.g.:

<int-http:inbound-gateway request-channel="httpMethodRouter"
    supported-methods="GET,DELETE"
    path="/process/{entId}"
    payload-expression="#pathVariables.entId"/>

<int:router input-channel="httpMethodRouter" expression="headers.http_requestMethod">
    <int:mapping value="GET" channel="in1"/>
    <int:mapping value="DELETE" channel="in2"/>
</int:router>

<int:service-activator input-channel="in1" ref="service" method="getEntity"/>

<int:service-activator input-channel="in2" ref="service" method="delete"/>

For more information regarding Handler Mappings, please see: Handler Mappings.

Starting with version 4.2 the <http:inbound-channel-adapter> and <http:inbound-gateway> can be configured with a <cross-origin> sub-element. It represents the same options as Spring MVC’s @CrossOrigin for @Controller methods and allows the configuration of Cross-origin resource sharing (CORS) for Spring Integration HTTP endpoints:

The CORS Java Configuration is represented by the org.springframework.integration.http.inbound.CrossOrigin class, instances of which can be injected to the HttpRequestHandlingEndpointSupport beans.

Starting with version 4.1 the <http:inbound-channel-adapter> can be configured with a status-code-expression to override the default 200 OK status. The expression must return an object which can be converted to an org.springframework.http.HttpStatus enum value. The evaluationContext has a BeanResolver but no variables, so the usage of this attribute is somewhat limited. An example might be to resolve, at runtime, some scoped Bean that returns a status code value but, most likely, it will be set to a fixed value such as status-code=expression="204" (No Content), or status-code-expression="T(org.springframework.http.HttpStatus).NO_CONTENT". By default, status-code-expression is null meaning that the normal 200 OK response status will be returned.

<http:inbound-channel-adapter id="inboundController"
       channel="requests" view-name="foo" error-code="oops"
       status-code-expression="T(org.springframework.http.HttpStatus).ACCEPTED">
   <request-mapping headers="BAR"/>
</http:inbound-channel-adapter>

The <http:inbound-gateway> resolves the status code from the http_statusCode header of the reply Message. Starting with version 4.2, the default response status code when no reply is received within the reply-timeout is 500 Internal Server Error. There are two ways to modify this behavior:

<int:chain input-channel="errors">
    <int:header-enricher>
        <int:header name="http_statusCode" value="504" />
    </int:header-enricher>
    <int:transformer expression="payload.failedMessage" />
</int:chain>

The payload of the ErrorMessage is a MessageTimeoutException; it must be transformed to something that can be converted by the gateway, such as a String; a good candidate is the exception’s message property, which is the value used when using the expression technique.

If the error flow times out after a main flow timeout, 500 Internal Server Error is returned, or the reply-timeout-status-code-expression is evaluated, if present.

	Note
	previously, the default status code for a timeout was 200 OK; to restore that behavior, set reply-timeout-status-code-expression="200".

By Using the path attribute in conjunction with the payload-expression attribute as well as the header sub-element, you have a high degree of flexibility for mapping inbound request data.

In the following example configuration, an Inbound Channel Adapter is configured to accept requests using the following URI: /first-name/{firstName}/last-name/{lastName}

Using the payload-expression attribute, the URI template variable {firstName} is mapped to be the Message payload, while the {lastName} URI template variable will map to the lname Message header.

<int-http:inbound-channel-adapter id="inboundAdapterWithExpressions"
    path="/first-name/{firstName}/last-name/{lastName}"
    channel="requests"
    payload-expression="#pathVariables.firstName">
    <int-http:header name="lname" expression="#pathVariables.lastName"/>
</int-http:inbound-channel-adapter>

For more information about URI template variables, please see the Spring Reference Manual: uri template patterns.

Since Spring Integration 3.0, in addition to the existing #pathVariables and #requestParams variables being available in payload and header expressions, other useful variables have been added.

The entire list of available expression variables:

Note, all these values (and others) can be accessed within expressions in the downstream message flow via the ThreadLocal org.springframework.web.context.request.RequestAttributes variable, if that message flow is single-threaded and lives within the request thread:

<int-:transformer
	expression="T(org.springframework.web.context.request.RequestContextHolder).
	              requestAttributes.request.queryString"/>

To configure the outbound gateway you can use the namespace support as well. The following code snippet shows the different configuration options for an outbound Http gateway. Most importantly, notice that the http-method and expected-response-type are provided. Those are two of the most commonly configured values. The default http-method is POST, and the default response type is null. With a null response type, the payload of the reply Message would contain the ResponseEntity as long as it’s http status is a success (non-successful status codes will throw Exceptions). If you are expecting a different type, such as a String, then provide that fully-qualified class name as shown below. See also the note about empty response bodies in Section 17.3, “Http Outbound Components”.

	Important
	Beginning with Spring Integration 2.1 the request-timeout attribute of the HTTP Outbound Gateway was renamed to reply-timeout to better reflect the intent.

<int-http:outbound-gateway id="example"
    request-channel="requests"
    url="http://localhost/test"
    http-method="POST"
    extract-request-payload="false"
    expected-response-type="java.lang.String"
    charset="UTF-8"
    request-factory="requestFactory"
    reply-timeout="1234"
    reply-channel="replies"/>

Important

Since Spring Integration 2.2, Java serialization over HTTP is no longer enabled by default. Previously, when setting the expected-response-type attribute to a Serializable object, the Accept header was not properly set up. Since Spring Integration 2.2, the SerializingHttpMessageConverter has now been updated to set the Accept header to application/x-java-serialized-object. However, because this could cause incompatibility with existing applications, it was decided to no longer automatically add this converter to the HTTP endpoints. If you wish to use Java serialization, you will need to add the SerializingHttpMessageConverter to the appropriate endpoints, using the message-converters attribute, when using XML configuration, or using the setMessageConverters() method. Alternatively, you may wish to consider using JSON instead which is enabled by simply having Jackson on the classpath.

Beginning with Spring Integration 2.2 you can also determine the HTTP Method dynamically using SpEL and the http-method-expression attribute. Note that this attribute is obviously murually exclusive with http-method You can also use expected-response-type-expression attribute instead of expected-response-type and provide any valid SpEL expression that determines the type of the response.

<int-http:outbound-gateway id="example"
    request-channel="requests"
    url="http://localhost/test"
    http-method-expression="headers.httpMethod"
    extract-request-payload="false"
    expected-response-type-expression="payload"
    charset="UTF-8"
    request-factory="requestFactory"
    reply-timeout="1234"
    reply-channel="replies"/>

If your outbound adapter is to be used in a unidirectional way, then you can use an outbound-channel-adapter instead. This means that a successful response will simply execute without sending any Messages to a reply channel. In the case of any non-successful response status code, it will throw an exception. The configuration looks very similar to the gateway:

<int-http:outbound-channel-adapter id="example"
    url="http://localhost/example"
    http-method="GET"
    channel="requests"
    charset="UTF-8"
    extract-payload="false"
    expected-response-type="java.lang.String"
    request-factory="someRequestFactory"
    order="3"
    auto-startup="false"/>

Note

To specify the URL; you can use either the url attribute or the url-expression attribute. The url is a simple string (with placedholders for URI variables, as described below); the url-expression is a SpEL expression, with the Message as the root object, enabling dynamic urls. The url resulting from the expression evaluation can still have placeholders for URI variables. In previous releases, some users used the place holders to replace the entire URL with a URI variable. Changes in Spring 3.1 can cause some issues with escaped characters, such as ?. For this reason, it is recommended that if you wish to generate the URL entirely at runtime, you use the url-expression attribute.

If your URL contains URI variables, you can map them using the uri-variable sub-element. This sub-element is available for the Http Outbound Gateway and the Http Outbound Channel Adapter.

<int-http:outbound-gateway id="trafficGateway"
    url="https://local.yahooapis.com/trafficData?appid=YdnDemo&amp;zip={zipCode}"
    request-channel="trafficChannel"
    http-method="GET"
    expected-response-type="java.lang.String">
    <int-http:uri-variable name="zipCode" expression="payload.getZip()"/>
</int-http:outbound-gateway>

The uri-variable sub-element defines two attributes: name and expression. The name attribute identifies the name of the URI variable, while the expression attribute is used to set the actual value. Using the expression attribute, you can leverage the full power of the Spring Expression Language (SpEL) which gives you full dynamic access to the message payload and the message headers. For example, in the above configuration the getZip() method will be invoked on the payload object of the Message and the result of that method will be used as the value for the URI variable named zipCode.

Since Spring Integration 3.0, HTTP Outbound Endpoints support the uri-variables-expression attribute to specify an Expression which should be evaluated, resulting in a Map for all URI variable placeholders within the URL template. It provides a mechanism whereby different variable expressions can be used, based on the outbound message. This attribute is mutually exclusive with the <uri-variable/> sub-element:

<int-http:outbound-gateway
     url="https://foo.host/{foo}/bars/{bar}"
     request-channel="trafficChannel"
     http-method="GET"
     uri-variables-expression="@uriVariablesBean.populate(payload)"
     expected-response-type="java.lang.String"/>

where uriVariablesBean might be:

public class UriVariablesBean {
	private static final ExpressionParser EXPRESSION_PARSER = new SpelExpressionParser();

	public Map<String, ?> populate(Object payload) {
		Map<String, Object> variables = new HashMap<String, Object>();
		if (payload instanceOf String.class)) {
			variables.put("foo", "foo"));
		}
		else {
			variables.put("foo", EXPRESSION_PARSER.parseExpression("headers.bar"));
		}
		return variables;
	}

}

	Note
	The uri-variables-expression must evaluate to a Map. The values of the Map must be instances of String or Expression. This Map is provided to an ExpressionEvalMap for further resolution of URI variable placeholders using those expressions in the context of the outbound Message.

IMPORTANT

Scenarios when we need to supply a dynamic set of URI variables on per message basis can be achieved with the custom url-expression and some utilities for building and encoding URL parameters:

url-expression="T(org.springframework.web.util.UriComponentsBuilder)
                           .fromHttpUrl('http://HOST:PORT/PATH')
                           .queryParams(payload)
                           .build()
                           .toUri()"

where queryParams() expects a MultiValueMap<String, String> as an argument, so a real set of URL query parameters can be build in advance, before performing request.

The whole queryString can also be presented as an uri variable:

<int-http:outbound-gateway id="proxyGateway" request-channel="testChannel"
              url="http://testServer/test?{queryString}">
    <int-http:uri-variable name="queryString" expression="'a=A&amp;b=B'"/>
</int-http:outbound-gateway>

In this case the URL encoding must be provided manually. For example the org.apache.http.client.utils.URLEncodedUtils#format() can be used for this purpose. A mentioned, manually built, MultiValueMap<String, String> can be converted to the the List<NameValuePair> format() method argument using this Java Streams snippet:

List<NameValuePair> nameValuePairs =
    params.entrySet()
            .stream()
            .flatMap(e -> e
                    .getValue()
                    .stream()
                    .map(v -> new BasicNameValuePair(e.getKey(), v)))
            .collect(Collectors.toList());

By default, the URL string is encoded (see UriComponentsBuilder) to the URI object before sending the request. In some scenarios with a non-standard URI (e.g. the RabbitMQ Rest API) it is undesirable to perform the encoding. The <http:outbound-gateway/> and <http:outbound-channel-adapter/> provide an encode-uri attribute. To disable encoding the URL, this attribute should be set to false (by default it is true). If you wish to partially encode some of the URL, this can be achieved using an expression within a <uri-variable/>:

<http:outbound-gateway url="http://somehost/%2f/fooApps?bar={param}" encode-uri="false">
          <http:uri-variable name="param"
            expression="T(org.apache.commons.httpclient.util.URIUtil)
                                             .encodeWithinQuery('Hello World!')"/>
</http:outbound-gateway>

This example demonstrates how simple it is to send a Multipart HTTP request via Spring’s RestTemplate and receive it with a Spring Integration HTTP Inbound Adapter. All we are doing is creating a MultiValueMap and populating it with multi-part data. The RestTemplate will take care of the rest (no pun intended) by converting it to a MultipartHttpServletRequest . This particular client will send a multipart HTTP Request which contains the name of the company as well as an image file with the company logo.

RestTemplate template = new RestTemplate();
String uri = "http://localhost:8080/multipart-http/inboundAdapter.htm";
Resource s2logo = 
   new ClassPathResource("org/springframework/samples/multipart/spring09_logo.png");
MultiValueMap map = new LinkedMultiValueMap();
map.add("company", "SpringSource");
map.add("company-logo", s2logo);
HttpHeaders headers = new HttpHeaders();
headers.setContentType(new MediaType("multipart", "form-data"));
HttpEntity request = new HttpEntity(map, headers);
ResponseEntity<?> httpResponse = template.exchange(uri, HttpMethod.POST, request, null);

That is all for the client.

On the server side we have the following configuration:

<int-http:inbound-channel-adapter id="httpInboundAdapter"
    channel="receiveChannel"
    path="/inboundAdapter.htm"
    supported-methods="GET, POST"/>

<int:channel id="receiveChannel"/>

<int:service-activator input-channel="receiveChannel">
    <bean class="org.springframework.integration.samples.multipart.MultipartReceiver"/>
</int:service-activator>

<bean id="multipartResolver"
    class="org.springframework.web.multipart.commons.CommonsMultipartResolver"/>

The httpInboundAdapter will receive the request, convert it to a Message with a payload that is a LinkedMultiValueMap. We then are parsing that in the multipartReceiver service-activator;

public void receive(LinkedMultiValueMap<String, Object> multipartRequest){
    System.out.println("### Successfully received multipart request ###");
    for (String elementName : multipartRequest.keySet()) {
        if (elementName.equals("company")){
            System.out.println("\t" + elementName + " - " +
                ((String[]) multipartRequest.getFirst("company"))[0]);
        }
        else if (elementName.equals("company-logo")){
            System.out.println("\t" + elementName + " - as UploadedMultipartFile: " +
                ((UploadedMultipartFile) multipartRequest
                    .getFirst("company-logo")).getOriginalFilename());
        }
    }
}

You should see the following output:

### Successfully received multipart request ###
   company - SpringSource
   company-logo - as UploadedMultipartFile: spring09_logo.png