场景：过滤器中获取参数Token并添加到请求头（用户认证兼容老系统）
请求头和请求参数是不能直接修改，也没有提供修改的方法，但是可以在过滤器和拦截器中使用HttpServletRequestWrapper包装类达到修改的目的。

一、实现HttpServletRequestWrapper接口，下面直接使用匿名类

package com.xxxx.web.filter;

import org.apache.commons.lang3.StringUtils;

import javax.servlet.*;

import javax.servlet.annotation.WebFilter;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletRequestWrapper;

import java.io.IOException;

import java.util.Enumeration;

@WebFilter

public class AuthHeaderSettingFilter implements Filter{

    @Override

    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {

        HttpServletRequestWrapper requestWrapper = new HttpServletRequestWrapper((HttpServletRequest) request) {

            /**

             * 当调用request.getHeader("token")时，则获取请求参数中token值并当做Header的值返回

             * @param name

             * @return

             */

            @Override

            public String getHeader(String name) {

                // 先从原本的Request中获取头，如果为空且名字为token，则从参数中查找并返回

                String superHeader = super.getHeader(name);

                if("token".equals(name) && StringUtils.isEmpty(superHeader)){

                    String token = request.getParameter("token");

                    if (StringUtils.isNotEmpty(token)) {

                        return token ;

                    }

                }

                return superHeader;

            }

        };

        chain.doFilter(requestWrapper,response);

    }

    @Override

    public void destroy() {

    }

}

二、HttpServletRequestWrapper、ServletRequestWrapper和HttpServletRequest接口中的很多方法都可以重写

1. 要想增加一个请求参数可以在HttpServletRequestWrapper中重写getParameter(String name)

    @Override

    public String getParameter(String name) {

        if("newParam".equals(name)){

            return "这是我新增加的参数";

        }

        return super.getParameter(name);

    }

    @Override

    public Map<String, String[]> getParameterMap() {

        HashMap<String, String[]> newMap = new HashMap<>();

        newMap.putAll(super.getParameterMap());

        newMap.put("newParam",new String[]{"这是我新增加的参数"}) ;

        return Collections.unmodifiableMap(newMap);

    }

    @Override

    public String[] getParameterValues(String name) {

        if("newParam".equals(name)){

            return new String[]{"这是我新增加的参数"};

        }

        return super.getParameterValues(name);

    }

注意： getParameterMap()返回的时一个不可修改的map ,不能直接向里面put值， 所以在重写这个方法时要自己new 一个HashMap ，然后在新建的map中放值，最后返回时必须调用Collections.unmodifiableMap(Map<? extends K, ? extends V> m) 把map改成不可变的

1. 结构

    

   

   image.png

 

image.png

参考：

• Safely add / modify Servlet request parameter values -- 可能要代理才能访问

作者：else05
链接：https://www.jianshu.com/p/a8c9d45775ea
来源：简书
简书著作权归作者所有，任何形式的转载都请联系作者获得授权并注明出处。

package com.mobile.web.common;

import org.springframework.web.filter.OncePerRequestFilter;

import javax.servlet.FilterChain;

import javax.servlet.ServletException;

import javax.servlet.http.Cookie;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletRequestWrapper;

import javax.servlet.http.HttpServletResponse;

import java.io.IOException;

import java.util.*;

/**

 * 自定义的过滤器,

 * Created by Administrator on 2017/6/19 0019.

 */

public class ModifyParametersFilter extends OncePerRequestFilter {

    @Override

    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)

            throws ServletException, IOException {

        // 修改cookie

        ModifyHttpServletRequestWrapper mParametersWrapper = new ModifyHttpServletRequestWrapper(request);

        String token = request.getHeader("token");

        if (token != null && !"".equals(token)) {

            mParametersWrapper.putCookie("JSESSIONID", token);

        }

        // finish

        filterChain.doFilter(mParametersWrapper, response);

    }

    /**

     * 修改cookie信息

     */

    private class ModifyHttpServletRequestWrapper extends HttpServletRequestWrapper {

        private Map<String, String> mapCookies;

        ModifyHttpServletRequestWrapper(HttpServletRequest request) {

            super(request);

            this.mapCookies = new HashMap<>();

        }

        void putCookie(String name, String value) {

            this.mapCookies.put(name, value);

        }

        public Cookie[] getCookies() {

            HttpServletRequest request = (HttpServletRequest) getRequest();

            Cookie[] cookies = request.getCookies();

            if (mapCookies == null || mapCookies.isEmpty()) {

                return cookies;

            }

            if (cookies == null || cookies.length == 0) {

                List<Cookie> cookieList = new LinkedList<>();

                for (Map.Entry<String, String> entry : mapCookies.entrySet()) {

                    String key = entry.getKey();

                    if (key != null && !"".equals(key)) {

                        cookieList.add(new Cookie(key, entry.getValue()));

                    }

                }

                if (cookieList.isEmpty()) {

                    return cookies;

                }

                return cookieList.toArray(new Cookie[cookieList.size()]);

            } else {

                List<Cookie> cookieList = new ArrayList<>(Arrays.asList(cookies));

                for (Map.Entry<String, String> entry : mapCookies.entrySet()) {

                    String key = entry.getKey();

                    if (key != null && !"".equals(key)) {

                        for (int i = 0; i < cookieList.size(); i++) {

                            if(cookieList.get(i).getName().equals(key)){

                                cookieList.remove(i);

                            }

                        }

                        cookieList.add(new Cookie(key, entry.getValue()));

                    }

                }

                return cookieList.toArray(new Cookie[cookieList.size()]);

            }

        }

    }

}

    <filter>

        <filter-name>ModifyParametersFilter</filter-name>

        <filter-class>com.xiyinli.web.common.ModifyParametersFilter</filter-class>

    </filter>

    <filter-mapping>

        <filter-name>ModifyParametersFilter</filter-name>

        <url-pattern>/*</url-pattern>

        <!-- 直接从客户端过来的请求以及通过forward过来的请求都要经过该过滤器 -->

        <dispatcher>REQUEST</dispatcher>

        <dispatcher>FORWARD</dispatcher>

    </filter-mapping>