請求亂碼、響應亂碼的解決方案

請求亂碼

客戶端發送請求常用方式是GET、POST

GET請求

1. 使用代碼轉換的方式
2. 修改tomcat配置文件server.xml的方式

代碼轉換

url

http://localhost:8080/HelloServlet/h5?username=王學武

servlet類

public class HelloServlet5 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String username = req.getParameter("username");
        //get請求過來的數據，在url地址欄上就已經經過編碼了，所以我們取到的就是亂碼
        System.out.println("username===" + username);
        
        //tomcat收到了這批數據，getParameter 默認使用ISO-8859-1去解碼
        //先讓文字回到ISO-8859-1對應的字節數組 ， 然后再按utf-8組拼字符串
        username = new String(username.getBytes("ISO-8859-1"), "UTF-8");
        System.out.println("username===" + username);
    }

}

console輸出

username===王学武
username===王學武　

修改tomcat配置文件

直接在tomcat里面做配置，在tomcat里面做設置處理 conf/server.xml 加上URIEncoding="utf-8"，以后get請求過來的數據永遠都是用UTF-8編碼

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

servlet類

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輸出

username===王學武

POST請求

設置請求體里面的文字編碼

request.setCharacterEncoding("UTF-8");

servlet類

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("設置請求體編碼后：name==="+name);
    }
    
}

console輸出

設置請求體編碼后：name===王五

如果在獲取參數后設置req.setCharacterEncoding("utf-8");就不會起作用

public class HelloServlet5 extends HttpServlet {

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String name = req.getParameter("username");
        System.out.println("設置請求體編碼前：name==="+name);
        System.out.println("-------------------------");
        
        req.setCharacterEncoding("utf-8");
        name = req.getParameter("username");
        System.out.println("設置請求體編碼后：name==="+name);
    }
    
}

console輸出

設置請求體編碼前：name===王五
-------------------------
設置請求體編碼后：name===王äº　

對GET方式不起作用

 url

http://localhost:8080/HelloServlet/h5?name=王學武

servlet類

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輸出

name===王学武　

響應亂碼

響應輸出有兩種方式

1. 字符流
2. 字節流

 

public class HelloServlet5 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //以字符流的方式寫數據
//        resp.getWriter().write("<h3>response...</h3><br/>");
//        resp.getWriter().write("<h3>response...</h3>");
//        resp.getWriter().flush();
        //以字節流的方式寫數據
        resp.getOutputStream().write("response...".getBytes());
    }
    
}

注：getWriter()，outPutStream在進行文件寫入操作只能用一個，否則會拋出java.lang.IllegalStateException: getWriter() has already been called for this response

 字符流輸出亂碼

public class HelloServlet5 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //以字符流的方式寫數據
        PrintWriter out = resp.getWriter();
        //out.write("<h3>響應輸出數據</h3><br/>");
        
        //1. 指定輸出到客戶端的時候，這些文字使用UTF-8編碼
        resp.setCharacterEncoding("UTF-8");
        //2. 直接規定瀏覽器看這份數據的時候，使用什么編碼來看。
        resp.setHeader("Content-Type", "text/html; charset=UTF-8");
        
        out.write("<h3>響應輸出數據</h3>");
    }
    
}

 

原因：必須在resp.getWriter()之前設置字符編碼操作

public class HelloServlet5 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        
        //1. 指定輸出到客戶端的時候，這些文字使用UTF-8編碼
        resp.setCharacterEncoding("UTF-8");
        //2. 直接規定瀏覽器看這份數據的時候，使用什么編碼來看。
        resp.setHeader("Content-Type", "text/html; charset=UTF-8");
        
        //以字符流的方式寫數據
        PrintWriter out = resp.getWriter();
        out.write("<h3>響應輸出數據</h3>");
    }
    
}

 

 修改servlet類的代碼

public class HelloServlet5 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        
        //1. 指定輸出到客戶端的時候，這些文字使用UTF-8編碼
        resp.setCharacterEncoding("UTF-8");
        //2. 直接規定瀏覽器看這份數據的時候，使用什么編碼來看。
        resp.setHeader("Content-Type", "text/html; charset=UTF-8");
        
        //以字符流的方式寫數據
        PrintWriter out = resp.getWriter();
        out.write("<h3>響應輸出數據</h3>");
    }
    
}

字節流輸出

public class HelloServlet5 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1. 指定瀏覽器看這份數據使用的碼表
        resp.setHeader("Content-Type", "text/html;charset=UTF-8");
        
        //2. 指定輸出的中文用的碼表
        resp.getOutputStream().write("響應輸出數據".getBytes("UTF-8"));
    }
}

其實，無論是字節流輸出還是字符流輸出，通用寫法：

1. response.setContentType("text/html;charset=UTF-8")
2. 寫輸出數據即可