字符编码理解
来源：互联网 发布：游戏编程招聘 编辑：程序博客网 时间：2024/05/18 03:04
public static void main(String[] args) throws UnsupportedEncodingException {String str1 = "中";/* 1、String str = "中"; str1存入字符串池中，java的编码UNICODE编码形式存储/U4e2d * 2、byte[] bGBK = str.getBytes("GBK"); 读出字符串str1(/U4e2d),并按照GBK编码，返回GBK编码下"中"字对应的字节数组。bGBK={d6,d0}; * 3、byte[] bUTF8 = str.getBytes("UTF-8"); 得到"中"字在UTF-8编码下的数组 bUTF8={e4,b8,ad}; * 4、String strGBK = new String(bGBK,"GBK"); 将bGBK按照"GBK"解码，得到d6d0在"GBK"编码下的字---"中"; * * 5、String strUTF8 = new String(bUTF8,"UTF-8"); 将bUTF8按照"UTF-8"解码，得到e4b8ad对应的"UTF-8"编码下的字---"中"; * * 6、乱码String strError = new String(bGBK,"UTF-8"); 将bGBK--d6d0按UTF-8解码，得到UTF-8编码下的d6d0对应的字，不一定是一个字了，可能两个，可能是"?"(无法识别时为"?") * 7、web会出现乱码，是因为网络上以字节数组传递数据，容器接收到请求后，会根据其默认的字符编码将byte[]转换成字符串，就可能出现6中所提到的现象。再转回去就可以了，String strRight = new String(strError.getBytes("容器默认编码")，"请求中的字符编码"); */byte[] b = str1.getBytes("GBK");for (int i = 0; i < b.length; i++) {System.out.println(">>>>" + Integer.toHexString(b[i] & 0xff));// 得到str1对应的GBK编码数组。}byte[] b1 = str1.getBytes("UTF-8");for (int i = 0; i < b1.length; i++) {System.out.println("<<<<" + Integer.toHexString(b1[i] & 0xff));// 得到str1对应的UTF-8编码数组。}String str2 = new String(str1.getBytes("GBK"), "UTF-8");System.out.println(str1);System.out.println(str2);}<%@ 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">
<form action="Web2Servlet" method="get"><input type="text" name="username" value="中国" /><input type="submit" value="提交"></form>
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {String str = request.getParameter("username");System.out.println("str= "+str);byte[] b2 = str.getBytes("UNICODE");byte[] b3 = new byte[3];b3[0] = b2[3];b3[1] = b2[5];b3[2] = b2[7];for(int i=0;i<b3.length;i++)System.out.println("b3["+i+"]="+Integer.toHexString(b3[i]&0xff));String test = new String(b3,"UTF-8");System.out.println("test: "+test);for(int i=0;i<b2.length;i++)System.out.println("b2["+i+"]="+Integer.toHexString(b2[i]&0xff));} tomcat未指定URIEncoding=utf-8时，tomcat将get提交按UNICODE进行编码。打印结果：str= ??????b3[0]=e4b3[1]=b8b3[2]=adtest: 中b2[0]=feb2[1]=ffb2[2]=0b2[3]=e4b2[4]=0b2[5]=b8b2[6]=0b2[7]=adb2[8]=0b2[9]=e5b2[10]=0b2[11]=9bb2[12]=0b2[13]=bdps:在eclipse下，直接new server更改URIEncoding的时候，需要在eclipse的server工程中修改。<%@ 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">
<form action="Web2Servlet" method="post"><input type="text" name="username" value="中国" /><input type="submit" value="提交"></form>
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {request.setCharacterEncoding("UTF-8");System.out.println("this is post method");String str = request.getParameter("username");System.out.println("str= "+str);}如果指定request.setCharacterEncoding("UTF-8");则正常显示。所以一般处理乱码，使用过滤器。如果不指定request.setCharacterEncoding("UTF-8");那么显示时和get方法提交是一样的，也就是tomcat使用了UNICODE对字节流进行编码。ps:过滤器和request.setCharacterEncoding("UTF-8");只对消息体有作用，对消息头无效。
