首先我們拿個簡單的登錄看一下

代碼實例如下:
我們先看一下錯誤的代碼
1.LoginServlet.java

import java.io.IOException; import java.io.PrintWriter;import javax.servlet.ServletException; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;import org.apache.logging.log4j.LogManager; import org.apache.logging.log4j.Logger; /*** 登錄驗證控制模塊* @author 演示**/public class LoginServlet extends BaseServlet {private static final Logger logger = LogManager.getLogger(LoginServlet.class);public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {this.doPost(request, response);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {login(request, response);}private void login(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {PrintWriter out = response.getWriter();response.setCharacterEncoding("utf-8");response.setContentType("text/html;charset=utf-8");String username = request.getParameter("userid");String pwd = request.getParameter("pwd");String path="welcome.jsp";try{if(username.equals("niuniu") && pwd.equals("0516")) {process(request, response, path);}else {out.println("用戶名或者密碼錯誤！");}}catch(Exception e){e.printStackTrace();path="error/500.jsp";}}}

頁面顯示亂碼

當我們改變代碼的順序再看

import java.io.IOException; import java.io.PrintWriter;import javax.servlet.ServletException; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;import org.apache.logging.log4j.LogManager; import org.apache.logging.log4j.Logger; /*** 登錄驗證控制模塊* @author 演示**/public class LoginServlet extends BaseServlet {private static final Logger logger = LogManager.getLogger(LoginServlet.class);public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {this.doPost(request, response);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {login(request, response);}private void login(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//設置編碼集，防止亂碼，這兩行必須放在最前面，即放在輸出流的前面response.setCharacterEncoding("utf-8");response.setContentType("text/html;charset=utf-8");PrintWriter out = response.getWriter();String username = request.getParameter("userid");String pwd = request.getParameter("pwd");String path="welcome.jsp";try{if(username.equals("niuniu") && pwd.equals("0516")) {process(request, response, path);}else {out.println("用戶名或者密碼錯誤！");}}catch(Exception e){e.printStackTrace();path="error/500.jsp";}}}

問題解決了

總結

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