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

适用于标准 Spring MVC 控制器方法。然而

@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。所以

@RequestMapping(method = { RequestMethod.HEAD })

确实可以完成这项工作！

---

如果你真的想用

@HeadMapping

，你可以自己创建：

import org.springframework.core.annotation.AliasFor;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import java.lang.annotation.*;

@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 W3 标准 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，但不应该返回 Body。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，如本 post

中所述