Servlet 采用 forward 时,页面出现汉字乱码问题

经常有人问到，在servlet里面forward到一个页面之后，浏览器总是汉字的乱码。经调试发现，是由于在servlet里面不能正确调用 response.getWriter()方法造成的。

servlet 如下，如果去掉注释，则会出现乱码

package test;

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.RequestDispatcher;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class TestServlet extends HttpServlet {

@Override

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

// PrintWriter out = response.getWriter();

RequestDispatcher requestDispatcher = request.getRequestDispatcher( " /test/test2.jsp " );

requestDispatcher.forward(request, response);

}

曾经尝试增加如下语句，问题依然存在

package test;

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.RequestDispatcher;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class TestServlet extends HttpServlet {

@Override

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

PrintWriter out = response.getWriter();

response.setCharacterEncoding( " UTF-8 " );

response.setContentType( " text/html;charset=UTF-8 " );

RequestDispatcher requestDispatcher = request.getRequestDispatcher( " /test/test2.jsp " );

requestDispatcher.forward(request, response);

}

去掉后，就可以正常显示汉字了，

再次测试，发现是语句的顺序有问题，需要调整为如下的代码即可

package test;

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.RequestDispatcher;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class TestServlet extends HttpServlet {

@Override

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

response.setCharacterEncoding( " UTF-8 " ); // 先指定输出流的编码

PrintWriter out = response.getWriter(); // 再拿到输出对象

response.setContentType( " text/html;charset=UTF-8 " );

RequestDispatcher requestDispatcher = request.getRequestDispatcher( " /test/test2.jsp " );

requestDispatcher.forward(request, response);

}

看来，response.getWriter() 在内部的实现上，影响了输出流的编码集。必须先指定编码集，再调用Writer才可以。

附test2.jsp的代码

<% @ page language = " java " contentType = " text/html; charset=UTF-8 " pageEncoding = " UTF-8 " %>

< pre > 中文

<%= " 中文2 " %>

</ pre >

web.xml, 未使用任何过滤器

<? xml version="1.0" encoding="UTF-8" ?>

< web-app id ="WebApp_ID" version ="2.4" xmlns ="http://java.sun.com/xml/ns/j2ee"

xmlns:xsi ="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation ="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" >

< display-name > www.java2000.net </ display-name >

< welcome-file-list >

< welcome-file > index.html </ welcome-file >

< welcome-file > index.htm </ welcome-file >

< welcome-file > index.jsp </ welcome-file >

< welcome-file > default.html </ welcome-file >

< welcome-file > default.htm </ welcome-file >

< welcome-file > default.jsp </ welcome-file >

</ welcome-file-list >

</ web-app >

Servlet 采用 forward 时,页面出现汉字乱码问题的分析

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