请求乱码、响应乱码的解决方案

请求乱码

客户端发送请求常用方式是GET、POST

GET请求

1. 使用代码转换的方式
2. 修改tomcat配置文件server.xml的方式

代码转换

url

http://localhost:8080/HelloServlet/h5?username=王学武

servlet类

public class HelloServlet5 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String username = req.getParameter("username");
        //get请求过来的数据，在url地址栏上就已经经过编码了，所以我们取到的就是乱码
        System.out.println("username===" + username);
        
        //tomcat收到了这批数据，getParameter 默认使用ISO-8859-1去解码
        //先让文字回到ISO-8859-1对应的字节数组 ， 然后再按utf-8组拼字符串
        username = new String(username.getBytes("ISO-8859-1"), "UTF-8");
        System.out.println("username===" + username);
    }

}

console输出

username===王学武
username===王学武　

修改tomcat配置文件

直接在tomcat里面做配置，在tomcat里面做设置处理 conf/server.xml 加上URIEncoding="utf-8"，以后get请求过来的数据永远都是用UTF-8编码

<Connector connectionTimeout="20000" port="8080" protocol="HTTP/1.1" redirectPort="8443" URIEncoding="utf-8"/>

servlet类

public class HelloServlet5 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String username = req.getParameter("username");
        System.out.println("username===" + username);
    }
}

console输出

username===王学武

POST请求

设置请求体里面的文字编码

request.setCharacterEncoding("UTF-8");

servlet类

public class HelloServlet5 extends HttpServlet {

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("utf-8");
        String name = req.getParameter("username");
        System.out.println("设置请求体编码后：name==="+name);
    }
    
}

console输出

设置请求体编码后：name===王五

如果在获取参数后设置req.setCharacterEncoding("utf-8");就不会起作用

public class HelloServlet5 extends HttpServlet {

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String name = req.getParameter("username");
        System.out.println("设置请求体编码前：name==="+name);
        System.out.println("-------------------------");
        
        req.setCharacterEncoding("utf-8");
        name = req.getParameter("username");
        System.out.println("设置请求体编码后：name==="+name);
    }
    
}

console输出

设置请求体编码前：name===王五
-------------------------
设置请求体编码后：name===王äº　

对GET方式不起作用

 url

http://localhost:8080/HelloServlet/h5?name=王学武

servlet类

public class HelloServlet5 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("utf-8");
        String name = req.getParameter("name");
        System.out.println("name==="+name);
    }
    
}

console输出

name===王学武　

响应乱码

响应输出有两种方式

1. 字符流
2. 字节流

public class HelloServlet5 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //以字符流的方式写数据
//        resp.getWriter().write("<h3>response...</h3><br/>");
//        resp.getWriter().write("<h3>response...</h3>");
//        resp.getWriter().flush();
        //以字节流的方式写数据
        resp.getOutputStream().write("response...".getBytes());
    }
    
}

注：getWriter()，outPutStream在进行文件写入操作只能用一个，否则会抛出java.lang.IllegalStateException: getWriter() has already been called for this response

 字符流输出乱码

public class HelloServlet5 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //以字符流的方式写数据
        PrintWriter out = resp.getWriter();
        //out.write("<h3>响应输出数据</h3><br/>");
        
        //1. 指定输出到客户端的时候，这些文字使用UTF-8编码
        resp.setCharacterEncoding("UTF-8");
        //2. 直接规定浏览器看这份数据的时候，使用什么编码来看。
        resp.setHeader("Content-Type", "text/html; charset=UTF-8");
        
        out.write("<h3>响应输出数据</h3>");
    }
    
}

原因：必须在resp.getWriter()之前设置字符编码操作

public class HelloServlet5 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        
        //1. 指定输出到客户端的时候，这些文字使用UTF-8编码
        resp.setCharacterEncoding("UTF-8");
        //2. 直接规定浏览器看这份数据的时候，使用什么编码来看。
        resp.setHeader("Content-Type", "text/html; charset=UTF-8");
        
        //以字符流的方式写数据
        PrintWriter out = resp.getWriter();
        out.write("<h3>响应输出数据</h3>");
    }
    
}

 修改servlet类的代码

public class HelloServlet5 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        
        //1. 指定输出到客户端的时候，这些文字使用UTF-8编码
        resp.setCharacterEncoding("UTF-8");
        //2. 直接规定浏览器看这份数据的时候，使用什么编码来看。
        resp.setHeader("Content-Type", "text/html; charset=UTF-8");
        
        //以字符流的方式写数据
        PrintWriter out = resp.getWriter();
        out.write("<h3>响应输出数据</h3>");
    }
    
}

字节流输出

public class HelloServlet5 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1. 指定浏览器看这份数据使用的码表
        resp.setHeader("Content-Type", "text/html;charset=UTF-8");
        
        //2. 指定输出的中文用的码表
        resp.getOutputStream().write("响应输出数据".getBytes("UTF-8"));
    }
}

其实，无论是字节流输出还是字符流输出，通用写法：

1. response.setContentType("text/html;charset=UTF-8")
2. 写输出数据即可