Rest映射原理

• 查看WebMvcAutoConfiguration，默认配置了OrderedHiddenHttpMethodFilter

@Configuration(proxyBeanMethods = false)
@ConditionalOnWebApplication(type = Type.SERVLET)
@ConditionalOnClass({ Servlet.class, DispatcherServlet.class, WebMvcConfigurer.class })
@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE + 10)
@AutoConfigureAfter({ DispatcherServletAutoConfiguration.class, TaskExecutionAutoConfiguration.class,
    ValidationAutoConfiguration.class })
public class WebMvcAutoConfiguration {

  public static final String DEFAULT_PREFIX = "";

  public static final String DEFAULT_SUFFIX = "";

  private static final String[] SERVLET_LOCATIONS = { "/" };

  @Bean
// 如果没有自定义的组件，则使用默认的组件
  @ConditionalOnMissingBean(HiddenHttpMethodFilter.class)
// 表示该配置需要开启，才能使用rest风格的请求
  @ConditionalOnProperty(prefix = "spring.mvc.hiddenmethod.filter", name = "enabled", matchIfMissing = false)
  public OrderedHiddenHttpMethodFilter hiddenHttpMethodFilter() {
    return new OrderedHiddenHttpMethodFilter();
  }

• 查看OrderedHiddenHttpMethodFilter

public class OrderedHiddenHttpMethodFilter extends HiddenHttpMethodFilter implements OrderedFilter {
    public static final int DEFAULT_ORDER = -10000;
    private int order = -10000;

    public OrderedHiddenHttpMethodFilter() {
    }

    public int getOrder() {
        return this.order;
    }

    public void setOrder(int order) {
        this.order = order;
    }
}

• 查看HiddenHttpMethodFilter，表示我们需要带1个隐藏的参数项_method

public class HiddenHttpMethodFilter extends OncePerRequestFilter {
    private static final List<String> ALLOWED_METHODS;
    public static final String DEFAULT_METHOD_PARAM = "_method";
    private String methodParam = "_method";

    public HiddenHttpMethodFilter() {
    }

    public void setMethodParam(String methodParam) {
        Assert.hasText(methodParam, "'methodParam' must not be empty");
        this.methodParam = methodParam;
    }

• Rest原理（表单提交要使用REST的时候）

● 表单提交会带上_method=PUT
● 请求过来被HiddenHttpMethodFilter拦截
  ○ 请求是否正常，并且是POST
    ■ 获取到_method的值。
    ■ 兼容以下请求；PUT.DELETE.PATCH
    ■ 原生request（post），包装模式requesWrapper重写了getMethod方法，返回的是传入的值。
    ■ 过滤器链放行的时候用wrapper。以后的方法调用getMethod是调用requesWrapper的。

• 测试

# 前端
测试REST风格；
<form action="/user" method="get">
    <input value="REST-GET 提交" type="submit"/>
</form>
<form action="/user" method="post">
    <input value="REST-POST 提交" type="submit"/>
</form>
<form action="/user" method="post">
    <input name="_method" type="hidden" value="delete"/>
    <input value="REST-DELETE 提交" type="submit"/>
</form>
<form action="/user" method="post">
    <input name="_method" type="hidden" value="PUT"/>
    <input value="REST-PUT 提交" type="submit"/>
</form>

# 后端
@RestController
public class HelloController {

    @RequestMapping(value = "/user",method = RequestMethod.GET)
    public String getUser(){
        return "GET-张三";
    }

    @RequestMapping(value = "/user",method = RequestMethod.POST)
    public String saveUser(){
        return "POST-张三";
    }


    @RequestMapping(value = "/user",method = RequestMethod.PUT)
    public String putUser(){
        return "PUT-张三";
    }

    @RequestMapping(value = "/user",method = RequestMethod.DELETE)
    public String deleteUser(){
        return "DELETE-张三";
    }

}

# yml
spring:
  mvc:
    hiddenmethod:
      filter:
        enabled: true   #开启页面表单的Rest功能

• 其他写法

@RestController
public class HelloController {

    @GetMapping("/user")
    public String getUser(){
        return "GET-张三";
    }

    @PostMapping("/user")
    public String saveUser(){
        return "POST-张三";
    }

    @PutMapping("/user")
    public String putUser(){
        return "PUT-张三";
    }

    @DeleteMapping("/user")
    public String deleteUser(){
        return "DELETE-张三";
    }

}

• 自定义filter：作用是将_mothod改为自定义字符

# 后端webConfig中配置：
    @Bean
    public HiddenHttpMethodFilter hiddenHttpMethodFilter(){
        HiddenHttpMethodFilter methodFilter = new HiddenHttpMethodFilter();
        methodFilter.setMethodParam("_m");
        return methodFilter;
    }

# 前端表单中：
<form action="/user" method="post">
    <input name="_m" type="hidden" value="delete"/>
    <input value="REST-DELETE 提交" type="submit"/>
</form>

# 手动开启HiddenHttpMethodFilter，yml中配置

# 后端控制器：
    @RequestMapping(value = "/user",method = RequestMethod.DELETE)
    public String deleteUser(){
        return "DELETE-张三";
    }