过滤器demo-编码统一处理

package com.loaderman.demo.a_loginFilter;

import java.io.IOException;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 编码处理统一写到这里(servlet中不需要再处理编码)
 *
 */
public class EncodingFilter implements Filter {

    // 过滤器业务处理方法：处理的公用的业务逻辑操作
    @Override
    public void doFilter(ServletRequest req, ServletResponse res,
                         FilterChain chain) throws IOException, ServletException {

        // 转型
        final HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) res;

        // 一、处理公用业务
        request.setCharacterEncoding("UTF-8");                    // POST提交有效
        response.setContentType("text/html;charset=UTF-8");

        /*
         * 出现GET中文乱码，是因为在request.getParameter方法内部没有进行提交方式判断并处理。
         * String name = request.getParameter("userName");
         *
         * 解决：对指定接口的某一个方法进行功能扩展，可以使用代理!
         *      对request对象(目标对象)，创建代理对象！
         */
        HttpServletRequest proxy =  (HttpServletRequest) Proxy.newProxyInstance(
                request.getClass().getClassLoader(),         // 指定当前使用的累加载器
                new Class[]{HttpServletRequest.class},         // 对目标对象实现的接口类型
                new InvocationHandler() {                    // 事件处理器
                    @Override
                    public Object invoke(Object proxy, Method method, Object[] args)
                            throws Throwable {
                        // 定义方法返回值
                        Object returnValue = null;
                        // 获取方法名
                        String methodName = method.getName();
                        // 判断：对getParameter方法进行GET提交中文处理
                        if ("getParameter".equals(methodName)) {

                            // 获取请求数据值【 <input type="text" name="userName">】
                            String value = request.getParameter(args[0].toString());    // 调用目标对象的方法

                            // 获取提交方式
                            String methodSubmit = request.getMethod(); // 直接调用目标对象的方法

                            // 判断如果是GET提交，需要对数据进行处理  (POST提交已经处理过了)
                            if ("GET".equals(methodSubmit)) {
                                if (value != null && !"".equals(value.trim())){
                                    // 处理GET中文
                                    value = new String(value.getBytes("ISO8859-1"),"UTF-8");
                                }
                            }
                            return value;
                        }
                        else {
                            // 执行request对象的其他方法
                            returnValue = method.invoke(request, args);
                        }

                        return returnValue;
                    }
                });

        // 二、放行 (执行下一个过滤器或者servlet)
        chain.doFilter(proxy, response);        // 传入代理对象
    }

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void destroy() {

    }
}

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>My JSP 'index.jsp' starting page</title>
    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
  </head>
  
  <body>
      <form name="frmLogin" action="${pageContext.request.contextPath }/login" method="post">
         用户名: <input type="text" name="userName"><br/>
        <input type="submit" value="POST提交" >
      </form>
      <hr/>
      <form name="frmLogin" action="${pageContext.request.contextPath }/login" method="get">
         用户名: <input type="text" name="userName"><br/>
        <input type="submit" value="GET提交" >
      </form>
  </body>
</html>

   <!--1.  编码处理过滤器配置     -->
    <filter>
        <filter-name>encoding</filter-name>
        <filter-class>com.loaderman.demo.a_loginFilter.EncodingFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>encoding</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

package com.loaderman.demo.a_loginFilter;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class LoginServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        // 获取请求数据
        String name = request.getParameter("userName");
        System.out.println("用户：" + name);
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        this.doGet(request, response);
    }

}