spring 接收_header 作为get请求的httpheader

今天项目遇到一个问题，我们项目用户验证和权限验证的信息（licence）是在http头中设置的，百度了一下，只有ajax才能设置头信息，form表单是无法设置的，但是我突然想起springMVC关于form表单解决put、delete提交方式的问题，我灵机一动，于是模仿springMVC实现了设置自定义header的功能。  

起源

项目使用的是SSM框架，废话不多说，我们先看springMVC对于form表单提交put、delete请求问题的解决方案，springMVC是使用了一个过滤器，使之用用户只需在form表单增加一个隐藏域_method即可，比如下面这样：

<form id="fm" method="post" >
        <input type="hidden" name="_method" value="put"/>
        <input type="hidden" name="_header" value="${licence }"/>
        <div class="fitem">
            <label>uNum:</label>
            <input name="uNum" class="easyui-validatebox" required="true">
        </div>
        <div class="fitem">
            <label>uPass:</label>
            <input name="uPass" class="easyui-validatebox" required="true">
        </div>
        <div class="fitem">
            <label>uName:</label>
            <input name="uName" class="easyui-validatebox" required="true">
        </div>
        <div class="fitem">
            <label>csId:</label>
            <input name="csId" class="easyui-validatebox" required="true">
        </div>
        <div class="fitem">
            <label>uJob:</label>
            <input name="uJob" class="easyui-validatebox" required="true">
        </div>
        <div class="fitem">
            <label>uStartTime:</label>
            <input name="uStartTime" class="easyui-validatebox" required="true">
        </div>
        <div class="fitem">
            <label>rId:</label>
            <input name="rId" class="easyui-validatebox" required="true">
        </div>
        <div class="fitem">
            <label>uMail:</label>
            <input name="uMail" class="easyui-validatebox" validType="email" required="true">
        </div>
        <div class="fitem">
            <label>uState:</label>
            <input name="uState" class="easyui-validatebox" required="true">
        </div>
    </form>

_method里的值就是你要提交方式，具体情况大家自己百度我就细说了。

实现

springmvc在web.xml中配置是这样的

<filter>
        <filter-name>httpMethodFilter</filter-name>
        <filter-class>org.springframework.web.filter.HiddenHttpMethodFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>httpMethodFilter</filter-name>
        <servlet-name>SpringMVC</servlet-name>
    </filter-mapping>

然后我们来看springMVC的源码：

/*
 * Copyright 2002-2012 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.filter;

import java.io.IOException;
import java.util.Locale;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import javax.servlet.http.HttpServletResponse;

import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

/**
 * {@link javax.servlet.Filter} that converts posted method parameters into HTTP methods,
 * retrievable via {@link HttpServletRequest#getMethod()}. Since browsers currently only
 * support GET and POST, a common technique - used by the Prototype library, for instance -
 * is to use a normal POST with an additional hidden form field ({@code _method})
 * to pass the "real" HTTP method along. This filter reads that parameter and changes
 * the {@link HttpServletRequestWrapper#getMethod()} return value accordingly.
 *
 * <p>The name of the request parameter defaults to {@code _method}, but can be
 * adapted via the {@link #setMethodParam(String) methodParam} property.
 *
 * <p><b>NOTE: This filter needs to run after multipart processing in case of a multipart
 * POST request, due to its inherent need for checking a POST body parameter.</b>
 * So typically, put a Spring {@link org.springframework.web.multipart.support.MultipartFilter}
 * <i>before</i> this HiddenHttpMethodFilter in your {@code web.xml} filter chain.
 *
 * @author Arjen Poutsma
 * @since 3.0
 */
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 {

        String paramValue = request.getParameter(this.methodParam);
        if ("POST".equals(request.getMethod()) && StringUtils.hasLength(paramValue)) {
            String method = paramValue.toUpperCase(Locale.ENGLISH);
            HttpServletRequest wrapper = new HttpMethodRequestWrapper(request, method);
            filterChain.doFilter(wrapper, response);
        }
        else {
            filterChain.doFilter(request, 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;
        }

        @Override
        public String getMethod() {
            return this.method;
        }
    }

}

重点我们来看他写的HttpMethodRequestWrapper这个内部类，这个类继承HttpServletRequestWrapper，而HttpServletRequestWrapper我进去看了下都是调用更上层的方法自己并没有做什么事情，再往上我就没去看了。我理解的他的原理是：request在得到method时时使用getMethod方法的，所以他重写了getMethod方法，从而可以把_method的值当做method。

那么既然这样，我也可以把_header的值当做header啊，而request获取header的方法是public String getHeader(String name)，所以我就写了下面这样的过滤器：

package com.zs.tools;

import java.io.IOException;

import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.filter.HiddenHttpMethodFilter;


/**
 * 张顺，2017-2-28
 * 处理form表单头的过滤器，
 * 如果表单有_header字段，可以自动将该字段转为request的header头信息（增加一条头）
 * @author it023
 */
public class MyHiddenHttpMethodFilter extends HiddenHttpMethodFilter{


    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
            throws ServletException, IOException {
        String header=request.getParameter("_header");
        if (header!=null && !header.trim().equals("")) {
            HttpServletRequest wrapper = new HttpHeaderRequestWrapper(request,header);
            super.doFilterInternal(wrapper, response, filterChain);
        }else {
            super.doFilterInternal(request, response, filterChain);
        }
    }

    private static class HttpHeaderRequestWrapper extends HttpServletRequestWrapper{

        private final String header;

        public HttpHeaderRequestWrapper(HttpServletRequest request,String licence) {
            super(request);
            this.header=licence;
        }

        @Override
        public String getHeader(String name) {
            if (name!=null &&
                    name.equals("licence") &&
                    super.getHeader("licence")==null) {
                return header;
            }else {
                return super.getHeader(name);
            }
        }

    }


}

然后，在web.xml中配置一下,我是放在HiddenHttpMethodFilter前面的。

<filter>
        <filter-name>httpHeaderFilter</filter-name>
        <filter-class>com.zs.tools.MyHiddenHttpMethodFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>httpHeaderFilter</filter-name>
        <servlet-name>SpringMVC</servlet-name>
    </filter-mapping>

结果

结果很成功，具体的代码我不想贴了，请看日志，这一条表示获取到http头的licence（不要在意licence为什么这么简单，那是因为这是测试数据）。

转自http://blog.csdn.net/fe123rarwa14235pp/article/details/58607296