JAVA反射(四)之动态代理解决全局乱码问题

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乱码出现的原因

在我们向服务端到客户端,或者相反,传送或者接收数据时候,如果编码解码不一致,就会出现乱码现象;

常见的几种中文编码格式: GB2312,iso-8859-1,UTF-8,GBK

Tomcat 默认的编码格式为:iso-8859-1

解决思路

解决乱码有很多办法,比如修改tomcat中config下面的web.xml文件,或者直接在接收发送的servlet中指定编码(麻烦,不推荐,每个servlet都要写重复的代码).

我今天向大家介绍动态代理解决全局乱码:

思路:
1.实现与HttpServletRequest相同接口的代理对象
2.在程序运行过程中对getParameter(String name)方法进行修改前逻辑的增强.
3.返回一个增强的HttpServletRequest对象

代码实现

总体视图
这里写图片描述

package com.tangbaobao.code;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.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/***@author 唐学俊*@Version 2017年11月18日上午8:58:10*使用动态代理来解决全局乱码问题*/public class CodeFilter implements Filter {    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)            throws IOException, ServletException {        //增强request,response        HttpServletRequest req = (HttpServletRequest) request;        HttpServletResponse resp = (HttpServletResponse) response;        req  = EnhanceRequest(req);        //放行        chain.doFilter(req, response);    }    private HttpServletRequest EnhanceRequest(HttpServletRequest req) {        //获取Proxy代理对象        HttpServletRequest EnhanceReq = (HttpServletRequest) Proxy.newProxyInstance(                req.getClass().getClassLoader(),                req.getClass().getInterfaces(),                new InvocationHandler() {                    @Override                    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {                        //获取对象方法                        String name = method.getName();                        if(name.equals("getParameter")) {                            //获取乱码的字符串                            String invoke = (String) method.invoke(req, args);                            invoke = new String(invoke.getBytes("iso-8859-1"),"UTF-8");                            return invoke;                        }                        return method.invoke(req, args);                    }                }            );        return EnhanceReq;    }}

package com.tangbaobao.code;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/***@author 唐学俊*@version 2017年11月18日上午9:44:14*接收客户端传递过来的表单*/public class IndexServlet extends HttpServlet {    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        String username = request.getParameter("username");        System.out.println(username);    }    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        doGet(request, response);    }}

 <%--客户端提交表单数据 --%><%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Insert title here</title></head><body><form action="${pageContext.request.contextPath }/index" method = "post">    <input type ="text" name ="username">    <input type = "submit" value = "提交"></form></body></html>

总结

相对传统的增强方法,使用动态代理解决全局乱码很方便;在使用以上方法解决全局乱码,记得把Filter作用域配置 /*,并且jsp页面的编码格式和workspace的编码格式都修改与你的理想编码格式一致;

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

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