Java

理解一下@RestControlle的作用

理解一下@RestControlle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=@Controller+@ResponseBody，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:

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{"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