@RestController的作用

原文：

文章收藏于IT老兵博客。

正文

理解一下@RestControlle的作用。

This code uses Spring 4’s new 

@RestController

 annotation, which marks the class as a controller where every method returns a domain object instead of a view. It’s shorthand for 

@Controller

 and 

@ResponseBody

 rolled together.

上文摘自官网。

由上面可见，@RestController[email protected][email protected]，下一步，理解@Controller。

Classic controllers can be annotated with the @Controller annotation. This is simply a specialization of the @Component class and allows implementation classes to be autodetected through the classpath scanning.

@Controller is typically used in combination with a @RequestMapping annotation used on request handling methods.

摘自这里，可以看出以下几点：

1. @Controller 是一种特殊化的@Component 类。
2. @Controller 习惯于和@RequestMapping绑定来使用，后者是用来指定路由映射的。

下一步，理解

@ResponseBody。

The request handling method is annotated with @ResponseBody. This annotation enables automatic serialization of the return object into the HttpResponse.

摘自同样的地方，这里可以看出：

1. @ResponseBody 是用来把返回对象自动序列化成HttpResponse的。

再参考这里：

3. @ResponseBody

The @ResponseBody annotation tells a controller that the object returned is automatically serialized into JSON and passed back into the HttpResponse object.

Suppose we have a custom Response object:

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public class ResponseTransfer { private String text; // standard getters/setters }

Next, the associated controller can be implemented:

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@Controller @RequestMapping ( "/post" ) public class ExamplePostController { @Autowired ExampleService exampleService; @PostMapping ( "/response" ) @ResponseBody public ResponseTransfer postResponseController( @RequestBody LoginForm loginForm) { return new ResponseTransfer( "Thanks For Posting!!!" ); } }

In the developer console of our browser or using a tool like Postman, we can see the following response:

1	{"text":"Thanks For Posting!!!"}

Remember, we don’t need to annotate the @RestController-annotated controllers with the @ResponseBody annotation since it’s done by default here.

从上面可以看出：

1. @ResponseBody告诉控制器返回对象会被自动序列化成JSON，并且传回HttpResponse这个对象。

再补充一下@RequestBody：

Simply put, the @RequestBody annotation maps the HttpRequest body to a transfer or domain object, enabling automatic deserialization of the inbound HttpRequest body onto a Java object.

First, let’s have a look at a Spring controller method:

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@PostMapping ( "/request" ) public ResponseEntity postController( @RequestBody LoginForm loginForm) { exampleService.fakeAuthenticate(loginForm); return ResponseEntity.ok(HttpStatus.OK); }

Spring automatically deserializes the JSON into a Java type assuming an appropriate one is specified. By default, the type we annotate with the @RequestBody annotation must correspond to the JSON sent from our client-side controller:

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public class LoginForm { private String username; private String password; // ... }

Here, the object we use to represent the HttpRequest body maps to our LoginForm object.

Let’s test this using CURL:

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curl -i \ -H "Accept: application/json" \ -H "Content-Type:application/json" \ -X POST --data '{"username": "johnny", "password": "password"}' "https://localhost:8080/.../request"

This is all that is needed for a Spring REST API and an Angular client using the @RequestBody annotation!

@RequestBody把HttpRequest body映射成一个 transfer or domain object（DTO或者DO），把一个入境（inbound）的HttpRequest的body反序列化成一个Java对象。

参考

https://spring.io/guides/gs/rest-service/

https://www.baeldung.com/spring-controller-vs-restcontroller

https://www.baeldung.com/spring-request-response-body