解决JSP&Servlet乱码问题

时间：2020-12-12 21:07:53

中文乱码


发生中文乱码的情况主要有三种:

1.表单form
(1)post
(2)get
2.超链接
< a href=”http://baidu.com?name=百度”>测试< /a>
3.sendRedirect()发生乱码
response.sendRedirect(“servlet地址?username=”君莫笑”“);

值得注意的是：乱码分为接收方和传送方。服务器(Tomcat)先接受，然后传送给浏览器

通过实例来解决：

简单的用户登录系统来完成。

先建一张表单，有用户名和密码。登陆后会把出现登陆成功字样，而且会显示登录名。
table.html 

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<h1>用户登录</h1>
<form action='/UserLoginOne/LoginClServlet' method='post'>
用户名:<input type='text' name='username'/> <br/>
密   码:<input type='password' name='password'/> <br/>
<input type='submit' value='登录'/> <br/>
</form>
</body>
</html>

密码验证：LoginClServlet.java 

public class LoginClServlet extends HttpServlet {

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    response.setContentType("text/html");


    PrintWriter out = response.getWriter();
    request.setCharacterEncoding("utf-8");
    //接受用户提交的用户名和密码
    String username = request.getParameter("username");
    String password = request.getParameter("password");
    //检验
    if("123".equals(password)){ 
        response.sendRedirect("/UserLoginOne/MainFrame?uname="+username);
    }else{
        response.sendRedirect("/UserLoginOne/table.html");
    }   
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    this.doGet(request, response);
}
}

显示页面：MainFrame.java

public class MainFrame extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    response.setContentType("text/html");
    request.setCharacterEncoding("utf-8");
    String name =request.getParameter("uname");
    PrintWriter out = response.getWriter();
    out.println("<h1>登录成功Welcome</h1>\n\n\n\n");
    out.println("username = "+name);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    this.doGet(request, response);
}

}

试验：
解决JSP&Servlet乱码问题
呵呵。。。不争气的东西登录二字就乱码了。。。不要慌 

response.setContentType("text/html");

原因主要是没有在这上面申明字符编码，先改为：

response.setContentType("text/html;charset=utf-8");
//把eclipse的编码改为utf-8,默认是GBK

成功了。。解决JSP&Servlet乱码问题
重点：不要把;写成，。本人就因为这个找了一晚上加一早上的错误。。。重新敲了一遍才发现。。*
不过用户名是中文时就乱码了。。。

1.表单——post

先不使用sendRedirect()方法，接收到数据后直接从服务器和浏览器打印
LoginClServlet.java 

public class LoginClServlet extends HttpServlet {

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    response.setContentType("text/html");


    PrintWriter out = response.getWriter();

    //接受用户提交的用户名和密码
    String username = request.getParameter("username");
    String password = request.getParameter("password");
    //检验
    if("123".equals(password)){ 
        System.out.println("username = "+username);
        out.println("username = "+username);
        //response.sendRedirect("/UserLoginOne/MainFrame?uname="+username);
    }else{
        response.sendRedirect("/UserLoginOne/table.html");
    }   
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    this.doGet(request, response);
}
}

结果解决JSP&Servlet乱码问题
LoginClServlet.java 改为：

public class LoginClServlet extends HttpServlet {

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    response.setContentType("text/html;charset=utf-8");

    PrintWriter out = response.getWriter();
    request.setCharacterEncoding("utf-8");
    //接受用户提交的用户名和密码
    String username = request.getParameter("username");
    String password = request.getParameter("password");
    //检验
    if("123".equals(password)){ 
        System.out.println("username = "+username);
        out.println("username = "+username);
        //response.sendRedirect("/UserLoginOne/MainFrame?uname="+username);
    }else{
        response.sendRedirect("/UserLoginOne/table.html");
    }   
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    this.doGet(request, response);
}
}

这样服务器和浏览器都默认以utf-8编码显示，结果：
解决JSP&Servlet乱码问题

2.表单——get

把table 改为
直接运行的话肯定还是乱码的

LoginClServlet.java

public class LoginClServlet extends HttpServlet {

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    response.setContentType("text/html;charset=utf-8");

    PrintWriter out = response.getWriter();
    //接受用户提交的用户名和密码
    String username = request.getParameter("username");
    String password = request.getParameter("password");
    //检验
    if("123".equals(password)){ 
    //服务器默认编码是"iso-8859-1"，这样就是把编码改为utf-8
        String uname = new String(username.getBytes("iso-8859-1"),"utf-8");
        System.out.println("username = "+uname);
        out.println("username = "+uname);
        //response.sendRedirect("/UserLoginOne/MainFrame?uname="+username);
    }else{
        response.sendRedirect("/UserLoginOne/table.html");
    }   
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    this.doGet(request, response);
}
}

结果解决JSP&Servlet乱码问题
当然自己干脆写个工具类
MyTools.java

package Tools;

public class MyTools {

public static String GetNewString(String str){
    String newstring ="";
    try{
        newstring = new String(str.getBytes("iso-8859-1"),"utf-8");

    }catch(Exception e){
        e.printStackTrace();
    }

    return newstring;

}
}

LoginClServlet.java

import Tools.MyTools;

public class LoginClServlet extends HttpServlet {

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    response.setContentType("text/html;charset=utf-8");

    PrintWriter out = response.getWriter();
    //接受用户提交的用户名和密码
    String username = request.getParameter("username");
    String password = request.getParameter("password");
    //检验
    if("123".equals(password)){ 
        String uname = MyTools.GetNewString(username);
        System.out.println("username = "+uname);
        out.println("username = "+uname);
        //response.sendRedirect("/UserLoginOne/MainFrame?uname="+username);
    }else{
        response.sendRedirect("/UserLoginOne/table.html");
    }   
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    this.doGet(request, response);
}
}

3.超链接

和get原理一样，直接用工具类就行了

4.sendRedirect()方法

根据table.html的传送方式看；我的是get.
LoginClServlet.java

public class LoginClServlet extends HttpServlet {

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    response.setContentType("text/html;charset=utf-8");

    PrintWriter out = response.getWriter();
    //接受用户提交的用户名和密码
    String username = request.getParameter("username");
    String password = request.getParameter("password");
    //检验
    if("123".equals(password)){ 
        response.sendRedirect("/UserLoginOne/MainFrame?uname="+username);
    }else{
        response.sendRedirect("/UserLoginOne/table.html");
    }   
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    this.doGet(request, response);
}
}

MainFrame.java

public class MainFrame extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    response.setContentType("text/html;charset=utf-8");

    PrintWriter out = response.getWriter();
    out.println("<h1>登录成功Welcome</h1>\n\n\n\n");
    String name =MyTools.GetNewString(request.getParameter("uname"));
    System.out.println("username 2= "+name);
    out.println("uname 1 = "+name);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    this.doGet(request, response);
}

结果：
解决JSP&Servlet乱码问题

乱码情况基本就这几种。

*补充：*
下载文件时，提示框可能是乱码：
解决方案： 

String temp = java.net.URLEncoder.encode("***(文件名)"，"utf-8");
response.setHeader("Content-Disposition","attachment;filename"+temp);

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