案例：验证码
案例：验证码
1. 案例需求：
1. 访问带有验证码的登录页面login.jsp
2. 用户输入用户名，密码以及验证码。
* 如果用户名和密码输入有误，跳转登录页面，提示:用户名或密码错误
* 如果验证码输入有误，跳转登录页面，提示：验证码错误
* 如果全部输入正确，则跳转到主页success.jsp，显示：用户名,欢迎您
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>用户名</td><td><input type="text" name="username"></td></tr><tr><td>密码</td><td><input type="password" name="password"></td></tr><tr><td>验证码</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="登录"></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.创建一对象，在内存中图片(验证码图片对象)BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);//2.美化图片//2.1 填充背景色Graphics g = image.getGraphics();//画笔对象g.setColor(Color.PINK);//设置画笔颜色g.fillRect(0,0,width,height);//2.2画边框g.setColor(Color.BLUE);g.drawRect(0,0,width - 1,height - 1);String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789";//生成随机角标Random ran = new Random();StringBuilder sb = new StringBuilder();for (int i = 1; i <= 4; i++) {int index = ran.nextInt(str.length());//获取字符char ch = str.charAt(index);//随机字符sb.append(ch);//2.3写验证码g.drawString(ch+"",width/5*i,height/2);}String checkCode_session = sb.toString();//将验证码存入sessionrequest.getSession().setAttribute("checkCode_session",checkCode_session);//2.4画干扰线g.setColor(Color.GREEN);//随机生成坐标点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.将图片输出到页面展示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.设置request编码request.setCharacterEncoding("utf-8");//2.获取参数String username = request.getParameter("username");String password = request.getParameter("password");String checkCode = request.getParameter("checkCode");//3.先获取生成的验证码HttpSession session = request.getSession();String checkCode_session = (String) session.getAttribute("checkCode_session");//删除session中存储的验证码session.removeAttribute("checkCode_session");//3.先判断验证码是否正确if(checkCode_session!= null && checkCode_session.equalsIgnoreCase(checkCode)){//忽略大小写比较//验证码正确//判断用户名和密码是否一致if("zhangsan".equals(username) && "123".equals(password)){//需要调用UserDao查询数据库//登录成功//存储信息，用户信息session.setAttribute("user",username);//重定向到success.jspresponse.sendRedirect(request.getContextPath()+"/success.jsp");}else{//登录失败//存储提示信息到requestrequest.setAttribute("login_error","用户名或密码错误");//转发到登录页面request.getRequestDispatcher("/login.jsp").forward(request,response);}}else{//验证码不一致//存储提示信息到requestrequest.setAttribute("cc_error","验证码错误");//转发到登录页面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")%>,欢迎您</h1></body> </html>注：验证码只用一次，下一次若要在使用验证码，则换成另外的一个验证码。一定要写下面的那一句代码。保证验证码只用一次
总结
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