为什么 @HeadMapping 在 Spring MVC 中不可用？

Question

Spring 框架中包含以下注释：
@GetMapping、@PostMapping、@PutMapping、@DeleteMapping 和 @PatchMapping 用于标准 Spring MVC 控制器方法。但是@HeadMapping 不是。这有什么意义？

Answer 1

根据W3 Standard的HEAD请求

9.4 HEAD

The HEAD method is identical to GET except that the server MUST NOT return a 
message-body in the response. The metainformation contained in the HTTP 
headers in response to a HEAD request SHOULD be identical to the information 
sent in response to a GET request. This method can be used for obtaining 
metainformation about the entity implied by the request without transferring 
the entity-body itself. This method is often used for testing hypertext 
links for validity, accessibility, and recent modification.

它是一个类似于GET 的请求方法，但不应返回正文。因此，您的 GET 方法也将有效地处理 HEAD 方法，但不返回响应正文。

因此，理想情况下，您可以使用@GetMapping 来处理HEAD 请求方法，并且可以使用Filter 来避免将响应返回给调用客户端，正如post 中所讨论的那样

Answer 2

您总是可以退回到@RequestMapping。此注解支持所有类型的 HTTP 方法。所以@RequestMapping(method = { RequestMethod.HEAD }) 确实可以胜任！

---

如果你真的要使用@HeadMapping，你可以自己创建：

@target({ ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@RequestMapping(method = { RequestMethod.HEAD})
public @interface HeadMapping {
    @AliasFor(annotation = RequestMapping.class)
    String name() default "";

    @AliasFor(annotation = RequestMapping.class)
    String[] value() default {};

    @AliasFor(annotation = RequestMapping.class)
    String[] path() default {};

    @AliasFor(annotation = RequestMapping.class)
    String[] params() default {};

    @AliasFor(annotation = RequestMapping.class)
    String[] headers() default {};

    @AliasFor(annotation = RequestMapping.class)
    String[] consumes() default {};

    @AliasFor(annotation = RequestMapping.class)
    String[] produces() default {};
}