JavaWeb学习记录（六）——用户登录功能之Session与验证码验证功能的实现

一、产生验证码的工具类

package blank.util;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.util.Random;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;

public class ImageUtil {
   private static int width = 80;
   private static int height = 30;

    private   static Random rd = new Random();

   public static BufferedImage createImage(HttpServletRequest request) {

       BufferedImage image = new BufferedImage(width, height,
               BufferedImage.TYPE_INT_RGB);
       Graphics g = image.getGraphics();
       setBackgroud(g);
       //绘制内容
       String content=drawContent(g);
       //存到session域中
       request.getSession().setAttribute("content", content);
       drawLines(g);
       return image;
   }
   private static void drawLines(Graphics g) {
       g.setColor(Color.orange);
       //干扰线
       for (int i = 0; i < 4; i++) {
           int x1 = rd.nextInt(80);
           int y1 = rd.nextInt(30);
           int x2 = rd.nextInt(80);
           int y2 = rd.nextInt(30);
           g.drawLine(x1, y1, x2, y2);
       }
   }
   private static String drawContent(Graphics g) {
       g.setColor(Color.black);
       String temp = "u7684u4e00u4e86u662fu6211u4e0du5728u4ebau4eecu6709u6765u4ed6u8fd9u4e0au7740u4e2au5730u5230u5927u91ccu8bf4u5c31u53bbu5b50u5f97u4e5fu548cu90a3u8981u4e0bu770bu5929u65f6u8fc7u51fau5c0fu4e48u8d77u4f60u90fdu628au597du8fd8u591au6ca1u4e3au53c8u53efu5bb6u5b66u53eau4ee5u4e3bu4f1au6837u5e74u60f3u751fu540cu8001u4e2du5341u4eceu81eau9762u524du5934u9053u5b83u540eu7136u8d70u5f88u50cfu89c1u4e24u7528";

       int len = temp.length();
       StringBuffer sb = new StringBuffer();
       for (int i = 0; i < 4; i++) {
           int index = rd.nextInt(len);
           sb.append(temp.charAt(index));
       }
       g.drawString(sb.toString(), 15, 18);
       return sb.toString();
   }
   private static void setBackgroud(Graphics g) {
       g.setColor(Color.gray);
       g.fillRect(0, 0, width, height);
   }
}

二、页面展示层

index.jsp

<body>
<c:if test="${flag }">
   <h3>用户登录</h3>
   <form action="./login.do?oper=login" method="post">
       <table>
           ${error }
           <tr>
               <td>用户名：</td>
               <td><input type="text" name="name" value="${name}"/></td>
           </tr>
           <tr>
               <td>密码：</td>
               <td><input type="password" name="pass" value="${pass }"></td>
           </tr>
           <tr>
               <td>验证码：</td>
               <td><input type="text" name="checkCode"><img src="./code.do" onclick="javascript:alert('刷新')" alt="验证码"/>${code }</td>
           </tr>
           <tr>
               <td colspan="2"><input type="submit" value="登录"/></td>
           </tr>
       </table>
   </form>
   </c:if>
</body>

三、servlet控制层

    private UserDao userDao = new UserDaoImpl();

   public void doGet(HttpServletRequest request, HttpServletResponse response)
           throws ServletException, IOException {
       request.setCharacterEncoding("UTF-8");
       String oper = request.getParameter("oper");
       HttpSession session = request.getSession();
       if ("pre".equals(oper)) {
           session.setAttribute("flag", true);//防止非法访问
           request.getRequestDispatcher("./login.jsp").forward(request,
                   response);
       } else if ("login".equals(oper)) {
           String content = (String) session.getAttribute("content"); //随机生成的验证码内容
           if (content == null) {
               request.getRequestDispatcher("./init.do").forward(request,
                       response);
           }

           String code = request.getParameter("checkCode");//用户输入的验证码
           boolean flag = false;
           if (code != null) {
               if (code.equals(content)) {       //验证码一致
                   flag = true;
               }
           }
           if (flag) {
               String name = request.getParameter("name");
               String pass = request.getParameter("pass");
               User user = null;
               user = userDao.checkLogin(name, pass);

               if (user != null) {
                   session.setAttribute("user", user);
                   request.getRequestDispatcher("./init.do").forward(request,
                           response);
               } else {
                   request.setAttribute("error", "用户名或密码错误");
                   session.setAttribute("name", name);
                   session.setAttribute("pass", pass);
                   request.getRequestDispatcher("./login.jsp").forward(
                           request, response);
               }
           } else {
               request.setAttribute("code", "验证错误");
               request.getRequestDispatcher("./login.do?oper=pre").forward(
                       request, response);
           }
       } else if ("delete".equals(oper)) {
           // session.invalidate();//删除session中所有的内存对象
           session.removeAttribute("user");
           request.getRequestDispatcher("./init.do")
                   .forward(request, response);
       }
   }

public class CheckCodeServlet extends HttpServlet {

   public void doGet(HttpServletRequest request, HttpServletResponse response)
           throws ServletException, IOException {

       response.setContentType("image/jpeg");
       ImageIO.write(ImageUtil.createImage(request), "jpeg", response.getOutputStream());
   }

   public void doPost(HttpServletRequest request, HttpServletResponse response)
           throws ServletException, IOException {
       doGet(request, response);
   }

}