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Spring @RequestMapping

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http://www.baeldung.com/spring-requestmapping


1. Overview

In this article, we’ll focus on one of the main annotations in Spring MVC –@RequestMapping.

Simply put, the annotation is used to map web requests to Spring Controller methods.

2. @RequestMapping Basics

Let’s start with a simple example – mapping an HTTP request to a method using some basic criteria.

2.1. @RequestMapping – by Path

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@RequestMapping(value = "/ex/foos", method = RequestMethod.GET)
@ResponseBody
publicString getFoosBySimplePath() {
    return"Get some Foos";
}

To test out this mapping with a simple curl command, run:

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curl -i http://localhost:8080/spring-rest/ex/foos

2.2. @RequestMapping – the HTTP Method

The HTTP method parameter has no default – so if we don’t specify a value, it’s going to map to any HTTP request.

Here’s a simple example, similar to the previous one – but this time mapped to an HTTP POST request:

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@RequestMapping(value = "/ex/foos", method = POST)
@ResponseBody
publicString postFoos() {
    return"Post some Foos";
}

To test the POST via a curl command:

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curl -i -X POST http://localhost:8080/spring-rest/ex/foos

3. RequestMapping and HTTP Headers

3.1. @RequestMapping with the headers Attribute

The mapping can be narrowed even further by specifying a header for the request:

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@RequestMapping(value = "/ex/foos", headers = "key=val", method = GET)
@ResponseBody
publicString getFoosWithHeader() {
    return"Get some Foos with Header";
}

And even multiple headers via the header attribute of @RequestMapping:

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@RequestMapping(
  value = "/ex/foos",
  headers = { "key1=val1","key2=val2"}, method = GET)
@ResponseBody
publicString getFoosWithHeaders() {
    return"Get some Foos with Header";
}

To test the operation, we’re going to use the curl header support:

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curl -i -H "key:val"http://localhost:8080/spring-rest/ex/foos

Note that for the curl syntax for separating the header key and the header value is a colon, same as in the HTTP spec, while in Spring the equals sign is used.

3.2. @RequestMapping Consumes and Produces

Mapping media types produced by a controller method is worth special attention – we can map a request based on its Accept header via the@RequestMapping headers attribute introduced above:

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@RequestMapping(
  value = "/ex/foos",
  method = GET,
  headers = "Accept=application/json")
@ResponseBody
publicString getFoosAsJsonFromBrowser() {
    return"Get some Foos with Header Old";
}

The matching for this way of defining the Accept header is flexible – it uses contains instead of equals, so a request such as the following would still map correctly:

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curl -H "Accept:application/json,text/html"
  http://localhost:8080/spring-rest/ex/foos

Starting with Spring 3.1, the @RequestMapping annotation now has the producesand the consumes attributes, specifically for this purpose:

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@RequestMapping(
  value = "/ex/foos",
  method = RequestMethod.GET,
  produces = "application/json"
)
@ResponseBody
publicString getFoosAsJsonFromREST() {
    return"Get some Foos with Header New";
}

Also, the old type of mapping with the headers attribute will automatically be converted to the new produces mechanism starting with Spring 3.1, so the results will be identical.

This is consumed via curl in the same way:

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curl -H "Accept:application/json"
  http://localhost:8080/spring-rest/ex/foos

Additionally, produces support multiple values as well:

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@RequestMapping(
  value = "/ex/foos",
  method = GET,
  produces = { "application/json","application/xml"}
)

Keep in mind that these – the old way and the new way of specifying the acceptheader – are basically the same mapping, so Spring won’t allow them together – having both these methods active would result in:

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Caused by: java.lang.IllegalStateException: Ambiguous mapping found.
Cannot map 'fooController'bean method
java.lang.String
org.baeldung.spring.web.controller
  .FooController.getFoosAsJsonFromREST()
to
{ [/ex/foos],
  methods=[GET],params=[],headers=[],
  consumes=[],produces=[application/json],custom=[]
}:
There is already 'fooController'bean method
java.lang.String
org.baeldung.spring.web.controller
  .FooController.getFoosAsJsonFromBrowser()
mapped.

A final note on the new produces and consumes mechanism – these behave differently from most other annotations: when specified at the type level, the method level annotations do not complement but override the type level information.

And of course, if you want to dig deeper into building a REST API with Spring –check out the new REST with Spring course.

4. RequestMapping with Path Variables

Parts of the mapping URI can be bound to variables via the @PathVariableannotation.

4.1. Single @PathVariable

A simple example with a single path variable:

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@RequestMapping(value = "/ex/foos/{id}", method = GET)
@ResponseBody
publicString getFoosBySimplePathWithPathVariable(
  @PathVariable("id")longid) {
    return"Get a specific Foo with id=" + id;
}

This can be tested with curl:

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curl http://localhost:8080/spring-rest/ex/foos/1

If the name of the method argument matches the name of the path variable exactly, then this can be simplified by using @PathVariable with no value:

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@RequestMapping(value = "/ex/foos/{id}", method = GET)
@ResponseBody
publicString getFoosBySimplePathWithPathVariable(
  @PathVariableString id) {
    return"Get a specific Foo with id=" + id;
}

Note that @PathVariable benefits from automatic type conversion, so we could have also declared the id as:

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@PathVariablelong id

4.2. Multiple @PathVariable

More complex URI may need to map multiple parts of the URI to multiple values:

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@RequestMapping(value = "/ex/foos/{fooid}/bar/{barid}", method = GET)
@ResponseBody
publicString getFoosBySimplePathWithPathVariables
  (@PathVariablelong fooid, @PathVariablelong barid) {
    return"Get a specific Bar with id=" + barid +
      " from a Foo with id=" + fooid;
}

This is easily tested with a curl in the same way:

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curl http://localhost:8080/spring-rest/ex/foos/1/bar/2

4.3. @PathVariable with RegEx

Regular expressions can also be used when mapping the @PathVariable; for example, we will restrict the mapping to only accept numerical values for the id:

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@RequestMapping(value = "/ex/bars/{numericId:[\\d]+}", method = GET)
@ResponseBody
publicString getBarsBySimplePathWithPathVariable(
  @PathVariable long numericId) {
    return"Get a specific Bar with id=" + numericId;
}

This will mean that the following URIs will match:

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http://localhost:8080/spring-rest/ex/bars/1

But this will not:

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http://localhost:8080/spring-rest/ex/bars/abc

Further reading:

Serve Static Resources with Spring

How to map and handle static resources with Spring MVC - use the simple configuration, then the 3.1 more flexible one and finally the new 4.1 resource resolvers.

Read more →

Getting Started with Forms in Spring MVC

Learn how to work with forms using Spring MVC - mapping a basic entity, submit, displaying errors.

Read more →

Http Message Converters with the Spring Framework

How to configure HttpMessageConverters for a REST API with Spring, and how to use these converters with the RestTemplate.

Read more →

5. RequestMapping with Request Parameters

@RequestMapping allows easy mapping of URL parameters with the@RequestParam annotation. 

We are now mapping a request to a URI such as:

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http://localhost:8080/spring-rest/ex/bars?id=100
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@RequestMapping(value = "/ex/bars", method = GET)
@ResponseBody
publicString getBarBySimplePathWithRequestParam(
  @RequestParam("id")longid) {
    return"Get a specific Bar with id=" + id;
}

We are then extracting the value of the id parameter using the@RequestParam(“id”) annotation in the controller method signature.

The send a request with the id parameter, we’ll use the parameter support incurl:

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curl -i -d id=100 http://localhost:8080/spring-rest/ex/bars

In this example, the parameter was bound directly without having been declared first.

For more advanced scenarios, @RequestMapping can optionally define the parameters – as yet another way of narrowing the request mapping:

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@RequestMapping(value = "/ex/bars", params = "id", method = GET)
@ResponseBody
publicString getBarBySimplePathWithExplicitRequestParam(
  @RequestParam("id")longid) {
    return"Get a specific Bar with id=" + id;
}

Even more flexible mappings are allowed – multiple params values can be set, and not all of them have to be used:

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@RequestMapping(
  value = "/ex/bars",
  params = { "id","second"},
  method = GET)
@ResponseBody
publicString getBarBySimplePathWithExplicitRequestParams(
  @RequestParam("id")longid) {
    return"Narrow Get a specific Bar with id=" + id;
}

And of course, a request to a URI such as:

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http://localhost:8080/spring-rest/ex/bars?id=100&second=something

Will always be mapped to the best match – which is the narrower match, which defines both the id and the second parameter.

6. RequestMapping Corner Cases

6.1. @RequestMapping – multiple paths mapped to the same controller method

Although a single @RequestMapping path value is usually used for a single controller method, this is just good practice, not a hard and fast rule – there are some cases where mapping multiple requests to the same method may be necessary. For that case, the value attribute of @RequestMapping does accept multiple mappings, not just a single one:

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@RequestMapping(
  value = { "/ex/advanced/bars","/ex/advanced/foos"},
  method = GET)
@ResponseBody
publicString getFoosOrBarsByPath() {
    return"Advanced - Get some Foos or Bars";
}

Now, both of these curl commands should hit the same method:

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curl -i http://localhost:8080/spring-rest/ex/advanced/foos
curl -i http://localhost:8080/spring-rest/ex/advanced/bars

6.2. @RequestMapping – multiple HTTP request methods to the same controller method

Multiple requests using different HTTP verbs can be mapped to the same controller method:

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@RequestMapping(
  value = "/ex/foos/multiple",
  method = { RequestMethod.PUT, RequestMethod.POST }
)
@ResponseBody
publicString putAndPostFoos() {
    return"Advanced - PUT and POST within single method";
}

With curl, both of these will now hit the same method:

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curl -i -X POST http://localhost:8080/spring-rest/ex/foos/multiple
curl -i -X PUT http://localhost:8080/spring-rest/ex/foos/multiple

6.3. @RequestMapping – a fallback for all requests

To implement a simple fallback for all requests using a particular HTTP method – for example, for a GET:

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@RequestMapping(value = "*", method = RequestMethod.GET)
@ResponseBody
publicString getFallback() {
    return"Fallback for GET Requests";
}

Or even for all requests:

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@RequestMapping(
  value = "*",
  method = { RequestMethod.GET, RequestMethod.POST ... })
@ResponseBody
publicString allFallback() {
    return"Fallback for All Requests";
}

7. New Request Mapping Shortcuts

Spring Framework 4.3 introduced a few new HTTP mapping annotations, all based on @RequestMapping:

  • @GetMapping
  • @PostMapping
  • @PutMapping
  • @DeleteMapping
  • @PatchMapping

These new annotations can improve the readability and reduce the verbosity of the code. Let us look at these new annotations in action by creating a RESTful API that supports CRUD operations:

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@GetMapping("/{id}")
publicResponseEntity<?> getBazz(@PathVariableString id){
    returnnew ResponseEntity<>(newBazz(id, "Bazz"+id), HttpStatus.OK);
}
 
@PostMapping
publicResponseEntity<?> newBazz(@RequestParam("name") String name){
    returnnew ResponseEntity<>(newBazz("5", name), HttpStatus.OK);
}
 
@PutMapping("/{id}")
publicResponseEntity<?> updateBazz(
  @PathVariableString id,
  @RequestParam("name") String name) {
    returnnew ResponseEntity<>(newBazz(id, name), HttpStatus.OK);
}
 
@DeleteMapping("/{id}")
publicResponseEntity<?> deleteBazz(@PathVariableString id){
    returnnew ResponseEntity<>(newBazz(id), HttpStatus.OK);
}

A deep dive into these can be found here.

8. Spring Configuration

The Spring MVC Configuration is simple enough – considering that ourFooController is defined in the following package:

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packageorg.baeldung.spring.web.controller;
 
@Controller
publicclass FooController { ... }

We simply need a @Configuration class to enable the full MVC support and configure classpath scanning for the controller:

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@Configuration
@EnableWebMvc
@ComponentScan({"org.baeldung.spring.web.controller"})
publicclass MvcConfig {
    //
}

9. Conclusion

This article focus on the @RequestMapping annotation in Spring – discussing a simple use case, the mapping of HTTP headers, binding parts of the URI with@PathVariable and working with URI parameters and the @RequestParamannotation.

If you’d like to learn how to use another core annotation in Spring MVC, you can explore the @ModelAttribute annotation here.

The full code from the article is available on Github. This is a Maven project, so it should be easy to import and run as it is.

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