JSP+servlet生成驗證碼並驗證

JSP+servlet生成驗證碼並驗證

生成驗證碼的基本過程是：

<%@ page language=java import=java.util.* pageEncoding=UTF-8%>
<%@ page import=java.awt.*,java.awt.image.BufferedImage,javax.imageio.ImageIO %>
     <%
      response.setHeader(Cache-Control, no-cache);
      int width=60,height=20;
      
      BufferedImage image=new BufferedImage( width,height,BufferedImage.TYPE_INT_RGB);
      //由bufferdImage對象獲得畫筆g
      Graphics g=image.getGraphics();
      //畫筆填充矩形
      g.setColor(new Color(200,200,200));
      g.fillRect(0, 0, width, height);
      //生成隨機數
      Random rd=new Random();
      int rdNum=rd.nextInt(8999)+1000;
      String rdstr=String.valueOf(rdNum);
      //把隨機數放入session中
      session.setAttribute(rdStr, rdstr);
      //畫筆g畫隨機數
      g.setColor(Color.BLUE);
      g.setFont(new Font(,Font.PLAIN,20));
      g.drawString(rdstr, 10, 20);//這裡的坐標是一個字符的左下角基線   
      //畫100個隨機點
      g.setColor(Color.green);
      for(int i=0;i<100;i++){
           int x=rd.nextInt(width);
           int y=rd.nextInt(height);
           g.drawOval(x, y, 1, 1);
      }
      //用ImageIO的靜態函數write輸出圖像
      ImageIO.write(image, JPEG, response.getOutputStream());
      out.clear();
      out=pageContext.popBody(); 
     %>

畫圖的基本思想是：

<%@ page language=java import=java.util.* pageEncoding=UTF-8%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+://+request.getServerName()+:+request.getServerPort()+path+/;
%>

package servlets;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class codeServlet extends HttpServlet {
    /**
     * The doPost method of the servlet. 

     *
     * This method is called when a form has its tag value method equals to post.
     * 
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //獲取表單的驗證碼
        String code=request.getParameter(yanzhengma);
          //獲取session中的驗證碼
          HttpSession session=request.getSession();
          String randstr=(String) session.getAttribute(rdStr);
          response.setCharacterEncoding(gb2312);//respons設為中文編碼

          PrintWriter out=response.getWriter();//獲得輸出寫出器
           if(code.equals(randstr)){//輸入的驗證碼和session保存的驗證碼相比較
                    out.println(恭喜你，驗證碼正確！);         
           }
           else{                
               //response.sendRedirect(/code/back.jsp);
               out.println(驗證碼錯誤！！);
           }          
    }
}

輸入結果是：