reponse_request中文乱码问题

中文乱码问题

1. 出现乱码的原因

1) 在计算机中数据以二进制的形式进行存储的, 数据的传输也是通二进制的形式

2）需要存字符，会出现字符与字节之间的转换 (输入字符 读到的字符)

3) 字符和字节之间如何实现转换？ 都是通过查码表

4) 字符到字节是编码，字节到字符是解码， 编码和解码用到了不同码表就会出现乱码问题

我们把字符到字节称为编码，字节到字符称为解码

即字符--->编码--->字节--->解码--->字符

如下例子解码编码一致

public class Demo01 {
    public static void main(String[] args) throws UnsupportedEncodingException {
        //字符--->编码--->字节--->解码--->字符
        String str = "中国";
        System.out.println(str);
        //编码
        byte[] bytes=str.getBytes();
        //解码
        String result=new String(bytes);
        String result1=new String(bytes,"utf-8");
        System.out.println(result);
        System.out.println(result1);
        
        
    }
}

2. 出现乱码的情况，编码错和解码错

1):解码错，

解码错 ，用错误的码表编码再用正确的码表解码可以解决

package com.bjsxt.web;

import java.io.UnsupportedEncodingException;

public class Demo02 {
    public static void main(String[] args) throws UnsupportedEncodingException {
        //字符--->编码--->字节--->解码--->字符
        String str = "中国";
        System.out.println(str);
        //编码
        byte[] bytes=str.getBytes("utf-8");
        //解码错
        String result=new String(bytes,"gbk");
        // 遇到乱码    解码错   用错误的码表编码   再用正确的码表解码
        result=new String(result.getBytes("gbk"),"utf-8");
        System.out.println(result);
            
    }
}

2)：编码错

编码错无药可救

package com.bjsxt.web;

import java.io.UnsupportedEncodingException;

public class Demo03 {
    /**
     * 编码错   无药可救
     */
    public static void main(String[] args) throws UnsupportedEncodingException {
        String data = "你好";

        // 编码
        byte[] bytes = data.getBytes("iso8859-1");

        for (byte b : bytes) {
            System.out.println(b);
        }

        // 解码
        String result = new String(bytes, "utf-8");

        System.out.println(result);
    }
}

3.Response对象乱码问题

1). response getOutputStream 只需要指定浏览器的解码方式(response.setHeader("content-type", "text/html;charset=utf-8")),即通知浏览器使用 utf-8编码(实际上是通知解码方式)

 

 

package com.bjsxt.web;

import java.io.IOException;
import java.io.OutputStream;

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

public class ResponseDemo02 extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String str = "中国";
        // 指定浏览器的解码方式
        // 通知浏览器 使用 utf-8 编码
        response.setHeader("content-type", "text/html;charset=utf-8");
        //获得输出流
        OutputStream out = response.getOutputStream();
        //编码   发送响应体
        out.write(str.getBytes("utf-8"));
    }

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

}

 

2). response getWriter方法获得字符流，用于向浏览器输出字符数据

需要指定response编码方式(response.setCharacterEncoding("utf-8"))，又需要指定浏览器解码方式(response.setHeader("content-type", "text/html;charset=utf-8")),由于这两个太常用了,于是tomcat把他们封装了成response.setContentType("text/html;charset=utf-8");

 

 

package com.bjsxt.web;

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 ResponseDemo03 extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        
        String data = "你好";
        
        // 指定response的编码
        //response.setCharacterEncoding("utf-8");
        
        // 指定浏览器的解码方式
        // 通知浏览器 使用 utf-8 编码
        // response.setHeader("content-type", "text/html;charset=utf-8");
        
        
        // 解决response 乱码  必须要位于第一次 调用  getWriter 之前
        response.setContentType("text/html;charset=utf-8");
        
        PrintWriter out = response.getWriter();        // new PrintWriter(outputstream, "utf-8")
            
        out.print("abcd");
        
        
        //此处需先编码
        out.print(data);
        
        //response.getOutputStream().write("abcd".getBytes("gbk"));
        
    }

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

        doGet(request, response);
    }

}

3.Request对象请求参数乱码问题

 request.setCharacterEncoding("utf-8");    // post方式一消息体发送 ,只对post方式有效 对消息头无效

package com.bjsxt.web;

import java.io.IOException;

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

public class RequestDemo04 extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //解码错
        
        
        //request以ios8859-1编码了
        String name = request.getParameter("name");
        //手动以ios8859-1解码
        byte[] bytes = name.getBytes("iso8859-1");
        //再以utf-8编码
        name = new String(bytes,"utf-8");
        System.out.println("name=" + name);

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //解码错
        
        
        // 设置request的编码
        // request.setCharacterEncoding("utf-8");    // post方式一消息体发送 ,只对post方式有效 对消息头无效

        // 获得请求参数
        request.setCharacterEncoding("utf-8");
        String name = request.getParameter("name");
        System.out.println("name=" + name);
    }

}