Improve Your Spring REST API, Part IV

Spring 4 is around the corner. Milestone releases has been available for a while, the first release candidate was released earlier today, and the final release is expected before the end of this year.

@RestController

One new feature that has been added is the @RestController annotation, which provide some syntactic sugar to your controller. Take a look at the following code snippet:

@RestController
class PersonController {

    @Autowired
    private PersonService personService;

    @RequestMapping(value = "/person/{id}",
            method = RequestMethod.GET,
            produces = MediaType.APPLICATION_JSON_VALUE)
    Person get(@PathVariable("id") String id) {
        return personService.find(id);
    }
}

Did you notice anything different? Ok, there is the new annotation on the class, an autowired dependency, a method that returns a domain object based on a path variable, so what? Look again, did you notice that the @ResponseBody annotation was missing from the method declaration? Despite that, the server will return a Person instance serialized to JSON in the response body. To make this possible, the @ResponseBody annotation has been promoted in Spring 4 to type level, which means it can be added to classes, interfaces and other annotations. Next, the new @RestController annotation is simply created by composing the @ResponseBody annotation with the existing @Controller annotation (copied from the source code):

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Controller
@ResponseBody
public @interface RestController {
}

Spring 4 RC1

To start using the @RestController annotation and explore other Spring 4 features today, you can add the Spring milestone repository to your list of Maven repositories:

 <repositories>
    <repository>
        <id>org.springframework.maven.milestone</id>
        <name>Spring Milestone Repository</name>
        <url>http://maven.springframework.org/milestone/</url>
    </repository>

    <!-- more repositories -->

</repositories>

and update your Spring dependencies to version 4.0.0.RC1, e.g.

<dependencies>
    <dependency>
        <groupid>org.springframework</groupid>
        <artifactid>spring-web</artifactid>
        <version>4.0.0.RC1</version>
    </dependency>

    <!-- more dependencies -->

</dependencies>