public class HiddenHttpMethodFilter extends OncePerRequestFilter {

    /** Default method parameter: {@code _method} */

    public static final String DEFAULT_METHOD_PARAM = "_method";

    private String methodParam = DEFAULT_METHOD_PARAM;

    /**

     * Set the parameter name to look for HTTP methods.

     * @see #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;

        //如果这是一个POST请求

        if ("POST".equals(request.getMethod()) && request.getAttribute(WebUtils.ERROR_EXCEPTION_ATTRIBUTE) == null) {

            //接着获取参数值比如：PUT、DELETE等

            String paramValue = request.getParameter(this.methodParam);

            //封装成的相应的请求

            if (StringUtils.hasLength(paramValue)) {

                requestToUse = new HttpMethodRequestWrapper(request, paramValue);

            }

        }

        //最后将请求发送给下一个filter

        filterChain.doFilter(requestToUse, response);

    }

    /**

     * Simple {@link HttpServletRequest} wrapper that returns the supplied method for

     * {@link HttpServletRequest#getMethod()}.

     */

    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;

        }

    }