1. 簡介
在本快速教程中，我們提供 Spring @RequestBody 和 @ResponseBody 註解的簡潔概述。
2.
簡單來説，@RequestBody 註解將 HttpRequest 的請求體映射到傳輸或域對象，從而自動反序列化傳入的 HttpRequest 請求體到 Java 對象。
首先，讓我們來看一個 Spring 控制器方法:
@PostMapping("/request")
public ResponseEntity postController(
@RequestBody LoginForm loginForm) {
exampleService.fakeAuthenticate(loginForm);
return ResponseEntity.ok(HttpStatus.OK);
}Spring 自動將 JSON 反序列化為 Java 類型，假設指定了適當的類型。
默認情況下，帶有 @RequestBody 註解的類型必須與來自客户端控制器的 JSON 對應的類型:
public class LoginForm {
private String username;
private String password;
// ...
}在這裏，我們使用的一個對象來表示 HttpRequest 請求體映射到我們的 LoginForm 對象。
讓我們使用 CURL 測試它:
curl -i \
-H "Accept: application/json" \
-H "Content-Type:application/json" \
-X POST --data
'{"username": "johnny", "password": "password"}' "https://localhost:8080/spring-boot-rest/post/request"這就是 Spring REST API 和使用 @RequestBody 註解的 Angular 客户端所需要的全部內容。
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:
public class ResponseTransfer {
private String text;
// standard getters/setters
}Next, the associated controller can be implemented:
@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:
{"text":"Thanks For Posting!!!"}Remember, we don’t need to annotate the -annotated controllers with the @ResponseBody annotation
3.1. Setting the Content Type
When we use the @ResponseBody annotation, we’re still able to explicitly set the content type that our method returns.
For that, we can use the @RequestMapping‘s produces attribute. Note that annotations like @PostMapping, @GetMapping, etc. define aliases for that parameter.
Let’s now add a new endpoint that sends a JSON response:
@PostMapping(value = "/content", produces = MediaType.APPLICATION_JSON_VALUE)
@ResponseBody
public ResponseTransfer postResponseJsonContent(
@RequestBody LoginForm loginForm) {
return new ResponseTransfer("JSON Content!");
}In the example, we used the MediaType.APPLICATION_JSON_VALUE constant. Alternatively, we can use application/json directly.
Next, let’s implement a new method, mapped to the same /content path, but returning XML content instead:
@PostMapping(value = "/content", produces = MediaType.APPLICATION_XML_VALUE)
@ResponseBody
public ResponseTransfer postResponseXmlContent(
@RequestBody LoginForm loginForm) {
return new ResponseTransfer("XML Content!");
}Now, depending on the value of an Accept parameter sent in the request’s header, we’ll get different responses.
Let’s see this in action:
curl -i \
-H "Accept: application/json" \
-H "Content-Type:application/json" \
-X POST --data
'{"username": "johnny", "password": "password"}' "https://localhost:8080/spring-boot-rest/post/content"The CURL command returns a JSON response:
HTTP/1.1 200
Content-Type: application/json
Transfer-Encoding: chunked
Date: Thu, 20 Feb 2020 19:43:06 GMT
{"text":"JSON Content!"}Now, let’s change the Accept parameter:
curl -i \
-H "Accept: application/xml" \
-H "Content-Type:application/json" \
-X POST --data
'{"username": "johnny", "password": "password"}' "https://localhost:8080/spring-boot-rest/post/content"As anticipated, we get an XML content this time:
HTTP/1.1 200
Content-Type: application/xml
Transfer-Encoding: chunked
Date: Thu, 20 Feb 2020 19:43:19 GMT
<ResponseTransfer><text>XML Content!</text></ResponseTransfer>4. 結論
我們為 Spring 應用構建了一個簡單的 Angular 客户端，演示瞭如何使用 @RequestBody 和 @ResponseBody 註解。
此外，我們還展示瞭如何設置內容類型，使用 @ResponseBody。
