Mapping Requests

See equivalent in the Servlet stack

This section discusses request mapping for annotated controllers.

@RequestMapping

See equivalent in the Servlet stack

The @RequestMapping annotation is used to map requests to controllers methods. It has various attributes to match by URL, HTTP method, request parameters, headers, and media types. You can use it at the class level to express shared mappings or at the method level to narrow down to a specific endpoint mapping.

There are also HTTP method specific shortcut variants of @RequestMapping:

  • @GetMapping

  • @PostMapping

  • @PutMapping

  • @DeleteMapping

  • @PatchMapping

The preceding annotations are Custom Annotations that are provided because, arguably, most controller methods should be mapped to a specific HTTP method versus using @RequestMapping, which, by default, matches to all HTTP methods. At the same time, a @RequestMapping is still needed at the class level to express shared mappings.

@RequestMapping cannot be used in conjunction with other @RequestMapping annotations that are declared on the same element (class, interface, or method). If multiple @RequestMapping annotations are detected on the same element, a warning will be logged, and only the first mapping will be used. This also applies to composed @RequestMapping annotations such as @GetMapping, @PostMapping, etc.

The following example uses type and method level mappings:

  • Java

  • Kotlin

@RestController
@RequestMapping("/persons")
class PersonController {

	@GetMapping("/{id}")
	public Person getPerson(@PathVariable Long id) {
		// ...
	}

	@PostMapping
	@ResponseStatus(HttpStatus.CREATED)
	public void add(@RequestBody Person person) {
		// ...
	}
}
@RestController
@RequestMapping("/persons")
class PersonController {

	@GetMapping("/{id}")
	fun getPerson(@PathVariable id: Long): Person {
		// ...
	}

	@PostMapping
	@ResponseStatus(HttpStatus.CREATED)
	fun add(@RequestBody person: Person) {
		// ...
	}
}

URI Patterns

See equivalent in the Servlet stack

You can map requests by using glob patterns and wildcards:

Pattern Description Example

?

Matches one character

"/pages/t?st.html" matches "/pages/test.html" and "/pages/t3st.html"

*

Matches zero or more characters within a path segment

"/resources/*.png" matches "/resources/file.png"

"/projects/*/versions" matches "/projects/spring/versions" but does not match "/projects/spring/boot/versions"

**

Matches zero or more path segments until the end of the path

"/resources/**" matches "/resources/file.png" and "/resources/images/file.png"

"/resources/**/file.png" is invalid as ** is only allowed at the end of the path.

{name}

Matches a path segment and captures it as a variable named "name"

"/projects/{project}/versions" matches "/projects/spring/versions" and captures project=spring

{name:[a-z]}+

Matches the regexp "[a-z]"+ as a path variable named "name"

"/projects/{project:[a-z]}/versions"` matches `"/projects/spring/versions"` but not `"/projects/spring1/versions"+

{*path}

Matches zero or more path segments until the end of the path and captures it as a variable named "path"

"/resources/{*file}" matches "/resources/images/file.png" and captures file=/images/file.png

Captured URI variables can be accessed with @PathVariable, as the following example shows:

  • Java

  • Kotlin

@GetMapping("/owners/{ownerId}/pets/{petId}")
public Pet findPet(@PathVariable Long ownerId, @PathVariable Long petId) {
	// ...
}
@GetMapping("/owners/{ownerId}/pets/{petId}")
fun findPet(@PathVariable ownerId: Long, @PathVariable petId: Long): Pet {
	// ...
}

You can declare URI variables at the class and method levels, as the following example shows:

  • Java

  • Kotlin

@Controller
@RequestMapping("/owners/{ownerId}") (1)
public class OwnerController {

	@GetMapping("/pets/{petId}") (2)
	public Pet findPet(@PathVariable Long ownerId, @PathVariable Long petId) {
		// ...
	}
}
1 Class-level URI mapping.
2 Method-level URI mapping. 
@Controller
@RequestMapping("/owners/{ownerId}") (1)
class OwnerController {

	@GetMapping("/pets/{petId}") (2)
	fun findPet(@PathVariable ownerId: Long, @PathVariable petId: Long): Pet {
		// ...
	}
}
1 Class-level URI mapping.
2 Method-level URI mapping.

URI variables are automatically converted to the appropriate type or a TypeMismatchException is raised. Simple types (int, long, Date, and so on) are supported by default and you can register support for any other data type. See Type Conversion and DataBinder.

URI variables can be named explicitly (for example, @PathVariable("customId")), but you can leave that detail out if the names are the same and you compile your code with the -parameters compiler flag.

The syntax {*varName} declares a URI variable that matches zero or more remaining path segments. For example /resources/{*path} matches all files under /resources/, and the "path" variable captures the complete path under /resources.

The syntax {varName:regex} declares a URI variable with a regular expression that has the syntax: {varName:regex}. For example, given a URL of /spring-web-3.0.5.jar, the following method extracts the name, version, and file extension:

  • Java

  • Kotlin

@GetMapping("/{name:[a-z-]+}-{version:\\d\\.\\d\\.\\d}{ext:\\.[a-z]+}")
public void handle(@PathVariable String version, @PathVariable String ext) {
	// ...
}
@GetMapping("/{name:[a-z-]+}-{version:\\d\\.\\d\\.\\d}{ext:\\.[a-z]+}")
fun handle(@PathVariable version: String, @PathVariable ext: String) {
	// ...
}

URI path patterns can also have embedded ${…​} placeholders that are resolved on startup through PropertySourcesPlaceholderConfigurer against local, system, environment, and other property sources. You can use this to, for example, parameterize a base URL based on some external configuration.

Spring WebFlux uses PathPattern and the PathPatternParser for URI path matching support. Both classes are located in spring-web and are expressly designed for use with HTTP URL paths in web applications where a large number of URI path patterns are matched at runtime.

Spring WebFlux does not support suffix pattern matching — unlike Spring MVC, where a mapping such as /person also matches to /person.*. For URL-based content negotiation, if needed, we recommend using a query parameter, which is simpler, more explicit, and less vulnerable to URL path based exploits.

Pattern Comparison

See equivalent in the Servlet stack

When multiple patterns match a URL, they must be compared to find the best match. This is done with PathPattern.SPECIFICITY_COMPARATOR, which looks for patterns that are more specific.

For every pattern, a score is computed, based on the number of URI variables and wildcards, where a URI variable scores lower than a wildcard. A pattern with a lower total score wins. If two patterns have the same score, the longer is chosen.

Catch-all patterns (for example, **, {*varName}) are excluded from the scoring and are always sorted last instead. If two patterns are both catch-all, the longer is chosen.

Consumable Media Types

See equivalent in the Servlet stack

You can narrow the request mapping based on the Content-Type of the request, as the following example shows:

  • Java

  • Kotlin

@PostMapping(path = "/pets", consumes = "application/json")
public void addPet(@RequestBody Pet pet) {
	// ...
}
@PostMapping("/pets", consumes = ["application/json"])
fun addPet(@RequestBody pet: Pet) {
	// ...
}

The consumes attribute also supports negation expressions — for example, !text/plain means any content type other than text/plain.

You can declare a shared consumes attribute at the class level. Unlike most other request mapping attributes, however, when used at the class level, a method-level consumes attribute overrides rather than extends the class-level declaration.

MediaType provides constants for commonly used media types — for example, APPLICATION_JSON_VALUE and APPLICATION_XML_VALUE.

Producible Media Types

See equivalent in the Servlet stack

You can narrow the request mapping based on the Accept request header and the list of content types that a controller method produces, as the following example shows:

  • Java

  • Kotlin

@GetMapping(path = "/pets/{petId}", produces = "application/json")
@ResponseBody
public Pet getPet(@PathVariable String petId) {
	// ...
}
@GetMapping("/pets/{petId}", produces = ["application/json"])
@ResponseBody
fun getPet(@PathVariable petId: String): Pet {
	// ...
}

The media type can specify a character set. Negated expressions are supported — for example, !text/plain means any content type other than text/plain.

You can declare a shared produces attribute at the class level. Unlike most other request mapping attributes, however, when used at the class level, a method-level produces attribute overrides rather than extend the class level declaration.

MediaType provides constants for commonly used media types — for example, APPLICATION_JSON_VALUE, APPLICATION_XML_VALUE.

Parameters and Headers

See equivalent in the Servlet stack

You can narrow request mappings based on query parameter conditions. You can test for the presence of a query parameter (myParam), for its absence (!myParam), or for a specific value (myParam=myValue). The following examples tests for a parameter with a value:

  • Java

  • Kotlin

@GetMapping(path = "/pets/{petId}", params = "myParam=myValue") (1)
public void findPet(@PathVariable String petId) {
	// ...
}
1 Check that myParam equals myValue. 
@GetMapping("/pets/{petId}", params = ["myParam=myValue"]) (1)
fun findPet(@PathVariable petId: String) {
	// ...
}
1 Check that myParam equals myValue.

You can also use the same with request header conditions, as the following example shows:

  • Java

  • Kotlin

@GetMapping(path = "/pets/{petId}", headers = "myHeader=myValue") (1)
public void findPet(@PathVariable String petId) {
	// ...
}
1 Check that myHeader equals myValue. 
@GetMapping("/pets/{petId}", headers = ["myHeader=myValue"]) (1)
fun findPet(@PathVariable petId: String) {
	// ...
}
1 Check that myHeader equals myValue.

HTTP HEAD, OPTIONS

See equivalent in the Servlet stack

@GetMapping and @RequestMapping(method=HttpMethod.GET) support HTTP HEAD transparently for request mapping purposes. Controller methods need not change. A response wrapper, applied in the HttpHandler server adapter, ensures a Content-Length header is set to the number of bytes written without actually writing to the response.

By default, HTTP OPTIONS is handled by setting the Allow response header to the list of HTTP methods listed in all @RequestMapping methods with matching URL patterns.

For a @RequestMapping without HTTP method declarations, the Allow header is set to GET,HEAD,POST,PUT,PATCH,DELETE,OPTIONS. Controller methods should always declare the supported HTTP methods (for example, by using the HTTP method specific variants — @GetMapping, @PostMapping, and others).

You can explicitly map a @RequestMapping method to HTTP HEAD and HTTP OPTIONS, but that is not necessary in the common case.

Custom Annotations

See equivalent in the Servlet stack

Spring WebFlux supports the use of composed annotations for request mapping. Those are annotations that are themselves meta-annotated with @RequestMapping and composed to redeclare a subset (or all) of the @RequestMapping attributes with a narrower, more specific purpose.

@GetMapping, @PostMapping, @PutMapping, @DeleteMapping, and @PatchMapping are examples of composed annotations. They are provided, because, arguably, most controller methods should be mapped to a specific HTTP method versus using @RequestMapping, which, by default, matches to all HTTP methods. If you need an example of how to implement a composed annotation, look at how those are declared.

@RequestMapping cannot be used in conjunction with other @RequestMapping annotations that are declared on the same element (class, interface, or method). If multiple @RequestMapping annotations are detected on the same element, a warning will be logged, and only the first mapping will be used. This also applies to composed @RequestMapping annotations such as @GetMapping, @PostMapping, etc.

Spring WebFlux also supports custom request mapping attributes with custom request matching logic. This is a more advanced option that requires sub-classing RequestMappingHandlerMapping and overriding the getCustomMethodCondition method, where you can check the custom attribute and return your own RequestCondition.

Explicit Registrations

See equivalent in the Servlet stack

You can programmatically register Handler methods, which can be used for dynamic registrations or for advanced cases, such as different instances of the same handler under different URLs. The following example shows how to do so:

  • Java

  • Kotlin

@Configuration
public class MyConfig {

	@Autowired
	public void setHandlerMapping(RequestMappingHandlerMapping mapping, UserHandler handler) (1)
			throws NoSuchMethodException {

		RequestMappingInfo info = RequestMappingInfo
				.paths("/user/{id}").methods(RequestMethod.GET).build(); (2)

		Method method = UserHandler.class.getMethod("getUser", Long.class); (3)

		mapping.registerMapping(info, handler, method); (4)
	}

}
1 Inject target handlers and the handler mapping for controllers.
2 Prepare the request mapping metadata.
3 Get the handler method.
4 Add the registration. 
@Configuration
class MyConfig {

	@Autowired
	fun setHandlerMapping(mapping: RequestMappingHandlerMapping, handler: UserHandler) { (1)

		val info = RequestMappingInfo.paths("/user/{id}").methods(RequestMethod.GET).build() (2)

		val method = UserHandler::class.java.getMethod("getUser", Long::class.java) (3)

		mapping.registerMapping(info, handler, method) (4)
	}
}
1 Inject target handlers and the handler mapping for controllers.
2 Prepare the request mapping metadata.
3 Get the handler method.
4 Add the registration.

@HttpExchange

See equivalent in the Servlet stack

While the main purpose of @HttpExchange is to abstract HTTP client code with a generated proxy, the HTTP Interface on which such annotations are placed is a contract neutral to client vs server use. In addition to simplifying client code, there are also cases where an HTTP Interface may be a convenient way for servers to expose their API for client access. This leads to increased coupling between client and server and is often not a good choice, especially for public API’s, but may be exactly the goal for an internal API. It is an approach commonly used in Spring Cloud, and it is why @HttpExchange is supported as an alternative to @RequestMapping for server side handling in controller classes.

For example:

  • Java

  • Kotlin

@HttpExchange("/persons")
interface PersonService {

	@GetExchange("/{id}")
	Person getPerson(@PathVariable Long id);

	@PostExchange
	void add(@RequestBody Person person);
}

@RestController
class PersonController implements PersonService {

	public Person getPerson(@PathVariable Long id) {
		// ...
	}

	@ResponseStatus(HttpStatus.CREATED)
	public void add(@RequestBody Person person) {
		// ...
	}
}
@HttpExchange("/persons")
interface PersonService {

	@GetExchange("/{id}")
	fun getPerson(@PathVariable id: Long): Person

	@PostExchange
	fun add(@RequestBody person: Person)
}

@RestController
class PersonController : PersonService {

	override fun getPerson(@PathVariable id: Long): Person {
		// ...
	}

	@ResponseStatus(HttpStatus.CREATED)
	override fun add(@RequestBody person: Person) {
		// ...
	}
}

@HttpExchange and @RequestMapping have differences. @RequestMapping can map to any number of requests by path patterns, HTTP methods, and more, while @HttpExchange declares a single endpoint with a concrete HTTP method, path, and content types.

For method parameters and returns values, generally, @HttpExchange supports a subset of the method parameters that @RequestMapping does. Notably, it excludes any server-side specific parameter types. For details, see the list for @HttpExchange and @RequestMapping.

@HttpExchange also supports a headers() parameter which accepts "name=value"-like pairs like in @RequestMapping(headers={}) on the client side. On the server side, this extends to the full syntax that @RequestMapping supports.