form表单put、delete形式提交解决

form表单只反对get和post的形式提交，而咱们应用restful格调必然要应用到@PUTmapping、@DELETEmapping等注解，那么在提交表单时的method=“put/delete”也要对应注解，上面来看看SpringMVC和SpringBoot的解决形式。

1、SpringMVC的解决

SpringMVC通过在web.xml中配置如下过滤器HiddenHttpMethodFilter解决；而后在页面上提交一个暗藏的input来实现；

1、配置HiddenHttpMethodFilter

<filter>        <filter-name>HttpMethodFilter</filter-name>        <filter-class>org.springframework.web.filter.HiddenHttpMethodFilter</filter-class>    </filter>    <filter-mapping>        <filter-name>HttpMethodFilter</filter-name>        <url-pattern>/*</url-pattern>    </filter-mapping>

2、表单解决

<form th:action="" method="post">    <!-- 发送put申请批改员工数据 1、SpringMVC中配置HiddenHttpMethodFilter； 2、页面创立一个Post表单； 3、创立一个暗藏的input项，name=_method，value就是咱们指定的申请形式； -->  <input type="hidden" name="_method" value="put" /> </form>
留神这里的name属性只能为_method,value为咱们想提交的形式；

2、SpringBoot的解决

SpringBoot曾经为咱们主动配置了HttpMethodFilter，SpringBoot2.2.0以上版本须要咱们手动开启配置；

1、开启配置

#开启hiddenmethod 过滤器spring.mvc.hiddenmethod.filter.enabled=true

2、表单解决
同上；

3、看看源码

Ctrl+N搜寻-WebMvcAutoConfiguration类
而后Ctrl+F搜寻-hiddenmethod
看看SpringBoot如何主动配置的
源码如下：
@Bean@ConditionalOnMissingBean(HiddenHttpMethodFilter.class)//意为当咱们配置文件中没找到这个前缀（prefix）为spring.mvc.hiddenmethod.filter的名为enabled的属性就不开启这项配置，即默认false；@ConditionalOnProperty(prefix = "spring.mvc.hiddenmethod.filter", name = "enabled", matchIfMissing = false)public OrderedHiddenHttpMethodFilter hiddenHttpMethodFilter() {   return new OrderedHiddenHttpMethodFilter();}
按住Ctrl并点击HiddenHttpMethodFilter.class，去看看过滤器的源码
public class HiddenHttpMethodFilter extends OncePerRequestFilter {    private static final List<String> ALLOWED_METHODS;//容许的办法    public static final String DEFAULT_METHOD_PARAM = "_method";    private String methodParam = "_method";//这就是name="_method"，也就是从页面拿到的参数    public HiddenHttpMethodFilter() {    }    public void setMethodParam(String methodParam) {        Assert.hasText(methodParam, "'methodParam' must not be empty");        this.methodParam = methodParam;    }    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {        HttpServletRequest requestToUse = request;        //这里if判断request是不是post，这也是为什么form必须为post的起因        if ("POST".equals(request.getMethod()) && request.getAttribute("javax.servlet.error.exception") == null) {                    //利用request.getParameter取到hidden的input传来的value；            String paramValue = request.getParameter(this.methodParam);                        //hasLength()判断paramValue不为空行将paramValue转为大写并赋值给method            if (StringUtils.hasLength(paramValue)) {            //这个method才是咱们真正想要的申请形式                String method = paramValue.toUpperCase(Locale.ENGLISH);                                //如果被容许的method中蕴含有咱们真正想要的申请形式                if (ALLOWED_METHODS.contains(method)) {                //就应用咱们心愿的申请形式，把不是咱们传的method过滤掉了                    requestToUse = new HiddenHttpMethodFilter.HttpMethodRequestWrapper(request, method);                }            }        }        filterChain.doFilter((ServletRequest)requestToUse, response);    }    //这里定义了3种容许的办法DELETE、PUT、PATCH    static {        ALLOWED_METHODS = Collections.unmodifiableList(Arrays.asList(HttpMethod.PUT.name(), HttpMethod.DELETE.name(), HttpMethod.PATCH.name()));    }        private static class HttpMethodRequestWrapper extends HttpServletRequestWrapper {        private final String method;        public HttpMethodRequestWrapper(HttpServletRequest request, String method) {            super(request);            this.method = method;        }        public String getMethod() {            return this.method;        }    }}