SpringMVC HiddenHttpMethodFilter的使用

HTTP协议里面，四个表示操作方式的动词：GET、POST、PUT、DELETE，它们分别对应四种基本的操作，

GET用来获取资源，POST用来新建资源，PUT用来更新资源，DELETE用来删除资源。

GET /order/1 HTTP/1.1：得到id=1的order

DELETE /order/1 HTTP/1.1：删除id=1的order

PUT /order/1 HTTP/1.1：更新id=1的order

POST /order HTTP/1.1：新增order   

浏览器的form表单只支持GET和POST请求，而DELETE和PUT请求并不支持。为解决这个题，Spring3.0添加了一个 HiddenHttpMethodFilter 过滤器，可以将带有_method参数的http post请求转换为put或delete请求。从而解决问题。

需要在web.xml文件中配置一个HiddenHttpMethodFilter：

public class HiddenHttpMethodFilter extends OncePerRequestFilter {
public static final String DEFAULT_METHOD_PARAM = "_method";
private String methodParam = DEFAULT_METHOD_PARAM;
public void setMethodParam(String methodParam) {
Assert.hasText(methodParam, "'methodParam' must not be empty");
this.methodParam = methodParam;
}
@Override
protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
throws ServletException, IOException {
HttpServletRequest requestToUse = request;
if ("POST".equals(request.getMethod()) && request.getAttribute(WebUtils.ERROR_EXCEPTION_ATTRIBUTE) == null) {
String paramValue = request.getParameter(this.methodParam);
if (StringUtils.hasLength(paramValue)) {
requestToUse = new HttpMethodRequestWrapper(request, paramValue);
}
}
filterChain.doFilter(requestToUse, response);
}
private static class HttpMethodRequestWrapper extends HttpServletRequestWrapper {
private final String method;
public HttpMethodRequestWrapper(HttpServletRequest request, String method) {
super(request);
this.method = method.toUpperCase(Locale.ENGLISH);
}
@Override
public String getMethod() {
return this.method;
}
}
}

我们可以看到：HttpMethodRequestWrapper即为请求与请求类型的封装。

<filter>
<filter-name>HiddenHttpMethodFilter</filter-name>
<filter-class>org.springframework.web.filter.HiddenHttpMethodFilter</filter-class>
</filter>

<filter-mapping>
<filter-name>HiddenHttpMethodFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

在使用时，需要发送post请求时携带一个 name="_method" 的隐藏域，其值可以为GET/POST/DELETE/PUT。

<form action="test9" method="post">
<input type="hidden" name="_method" value="GET"/>
<input type="submit" value="GET"/>
</form>
<form action="test10" method="post">
<input type="hidden" name="_method" value="POST"/>
<input type="submit" value="POST"/>
</form>
<form action="test11" method="post">
<input type="hidden" name="_method" value="DELETE"/>
<input type="submit" value="DELETE"/>
</form>
<form action="test12" method="post">
<input type="hidden" name="_method" value="PUT"/>
<input type="submit" value="PUT"/>
</form>

在RequestMapping注解中配置method属性值：

public enum RequestMethod {

GET, HEAD, POST, PUT, PATCH, DELETE, OPTIONS, TRACE

}

@RequestMapping(value = "/test9", method = RequestMethod.GET)
@ResponseBody
public String test9() {
return "GET";
}
@RequestMapping(value = "/test10", method = RequestMethod.POST)
@ResponseBody
public String test10() {

return "POST";
}
@RequestMapping(value = "/test11", method = RequestMethod.DELETE)
@ResponseBody
public String test11() {

return "DELETE";
}
@RequestMapping(value = "/test12", method = RequestMethod.PUT)
@ResponseBody
public String test12() {

return "PUT";
}

当然_method属性也是可以自定义的：

<init-param>
<param-name>methodParam</param-name>
<param-value>_xiya</param-value>
</init-param>