为什么 @HeadMapping 在 Spring MVC 中不可用？

Question

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

Answer 1

你总是可以回到@RequestMapping. 该注解支持所有类型的 HTTP 方法。@RequestMapping(method = { RequestMethod.HEAD })工作也是如此！

如果你确实想使用@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 {};
}

Answer 2

根据HEAD 请求的W3 标准

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.

它是一种类似于GET但不应该返回 Body 的请求方法。因此，您的GET方法也将有效地处理该HEAD方法，但不返回响应正文。

因此，理想情况下，您可以使用它@GetMapping来处理HEAD请求方法，并且可以避免Filter将响应返回给调用客户端，如本文所述