案例：验证码
案例：驗證碼
1. 案例需求：
?? ?1. 訪問帶有驗證碼的登錄頁面login.jsp
?? ?2. 用戶輸入用戶名，密碼以及驗證碼。
?? ??? ?* 如果用戶名和密碼輸入有誤，跳轉登錄頁面，提示:用戶名或密碼錯誤
?? ??? ?* 如果驗證碼輸入有誤，跳轉登錄頁面，提示：驗證碼錯誤
?? ??? ?* 如果全部輸入正確，則跳轉到主頁success.jsp，顯示：用戶名,歡迎您
login.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head><title>login</title><script>window.onload = function(){document.getElementById("img").onclick = function(){this.src="/day16/checkCodeServlet?time="+new Date().getTime();}}</script><style>div{color: red;}</style> </head> <body><form action="/day16/loginServlet" method="post"><table><tr><td>用戶名</td><td><input type="text" name="username"></td></tr><tr><td>密碼</td><td><input type="password" name="password"></td></tr><tr><td>驗證碼</td><td><input type="text" name="checkCode"></td></tr><tr><td colspan="2"><img id="img" src="/day16/checkCodeServlet"></td></tr><tr><td colspan="2"><input type="submit" value="登錄"></td></tr></table></form><div><%=request.getAttribute("cc_error") == null ? "" : request.getAttribute("cc_error")%></div><div><%=request.getAttribute("login_error") == null ? "" : request.getAttribute("login_error") %></div> </body> </html>checkCodeServlet.java
package servlet;import javax.imageio.ImageIO; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.awt.*; import java.awt.image.BufferedImage; import java.io.IOException; import java.util.Random;@WebServlet("/checkCodeServlet") public class CheckCodeServlet extends HttpServlet {protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {int width = 100;int height = 50;//1.創建一對象，在內存中圖片(驗證碼圖片對象)BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);//2.美化圖片//2.1 填充背景色Graphics g = image.getGraphics();//畫筆對象g.setColor(Color.PINK);//設置畫筆顏色g.fillRect(0,0,width,height);//2.2畫邊框g.setColor(Color.BLUE);g.drawRect(0,0,width - 1,height - 1);String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789";//生成隨機角標Random ran = new Random();StringBuilder sb = new StringBuilder();for (int i = 1; i <= 4; i++) {int index = ran.nextInt(str.length());//獲取字符char ch = str.charAt(index);//隨機字符sb.append(ch);//2.3寫驗證碼g.drawString(ch+"",width/5*i,height/2);}String checkCode_session = sb.toString();//將驗證碼存入sessionrequest.getSession().setAttribute("checkCode_session",checkCode_session);//2.4畫干擾線g.setColor(Color.GREEN);//隨機生成坐標點for (int i = 0; i < 10; i++) {int x1 = ran.nextInt(width);int x2 = ran.nextInt(width);int y1 = ran.nextInt(height);int y2 = ran.nextInt(height);g.drawLine(x1,y1,x2,y2);}//3.將圖片輸出到頁面展示ImageIO.write(image,"jpg",response.getOutputStream());}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doPost(request,response);} }LoginServlet.java
package servlet;import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; import java.io.IOException;@WebServlet("/loginServlet") public class LoginServlet extends HttpServlet {protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//1.設置request編碼request.setCharacterEncoding("utf-8");//2.獲取參數String username = request.getParameter("username");String password = request.getParameter("password");String checkCode = request.getParameter("checkCode");//3.先獲取生成的驗證碼HttpSession session = request.getSession();String checkCode_session = (String) session.getAttribute("checkCode_session");//刪除session中存儲的驗證碼session.removeAttribute("checkCode_session");//3.先判斷驗證碼是否正確if(checkCode_session!= null && checkCode_session.equalsIgnoreCase(checkCode)){//忽略大小寫比較//驗證碼正確//判斷用戶名和密碼是否一致if("zhangsan".equals(username) && "123".equals(password)){//需要調用UserDao查詢數據庫//登錄成功//存儲信息，用戶信息session.setAttribute("user",username);//重定向到success.jspresponse.sendRedirect(request.getContextPath()+"/success.jsp");}else{//登錄失敗//存儲提示信息到requestrequest.setAttribute("login_error","用戶名或密碼錯誤");//轉發到登錄頁面request.getRequestDispatcher("/login.jsp").forward(request,response);}}else{//驗證碼不一致//存儲提示信息到requestrequest.setAttribute("cc_error","驗證碼錯誤");//轉發到登錄頁面request.getRequestDispatcher("/login.jsp").forward(request,response);}}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doPost(request, response);} }success.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head><title>Title</title> </head> <body><h1><%=request.getSession().getAttribute("user")%>,歡迎您</h1></body> </html>注：驗證碼只用一次，下一次若要在使用驗證碼，則換成另外的一個驗證碼。一定要寫下面的那一句代碼。保證驗證碼只用一次
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