JSP Servlet實現驗證碼

  1 package net.cmono.javaweb.c3;
  2 
  3 import java.awt.Color;
  4 import java.awt.Font;
  5 import java.awt.Graphics2D;
  6 import java.awt.image.BufferedImage;
  7 import java.io.IOException;
  8 import java.io.PrintWriter;
  9 import java.util.Random;
 10 
 11 import javax.servlet.ServletException;
 12 import javax.servlet.ServletOutputStream;
 13 import javax.servlet.http.HttpServlet;
 14 import javax.servlet.http.HttpServletRequest;
 15 import javax.servlet.http.HttpServletResponse;
 16 
 17 import com.sun.corba.se.impl.ior.NewObjectKeyTemplateBase;
 18 import com.sun.image.codec.jpeg.JPEGCodec;
 19 import com.sun.image.codec.jpeg.JPEGImageEncoder;
 20 
 21 public class IdentityServlet extends HttpServlet {
 22 
 23     /**
 24      * Constructor of the object.
 25 */
 26     public IdentityServlet() {
 27         super();
 28     }
 29 
 30     /**
 31      * Destruction of the servlet. <br>
 32 */
 33     public void destroy() {
 34         super.destroy(); // Just puts "destroy" string in log
 35 // Put your code here
 36     }
 37 
 38     /**
 39      * The doGet method of the servlet. <br>
 40      *
 41      * This method is called when a form has its tag value method equals to get.
 42      * 
 43      * @param request the request send by the client to the server
 44      * @param response the response send by the server to the client
 45      * @throws ServletException if an error occurred
 46      * @throws IOException if an error occurred
 47 */
 48     public void doGet(HttpServletRequest request, HttpServletResponse response)
 49             throws ServletException, IOException {
 50 
 51         response.setContentType("image/jpeg");
 52         
 53         String randomString = getRandomString();
 54         request.getSession(true).setAttribute("randomString",randomString);
 55         
 56         int width = 100;
 57         int height = 30;
 58         
 59         Color color = getRandomColor();
 60         Color reverse = getReverseColor(color);
 61         
 62         BufferedImage bi = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
 63         
 64         Graphics2D g = bi.createGraphics();
 65         g.setFont(new Font(Font.SANS_SERIF,Font.BOLD,16));
 66         g.setColor(color);
 67         g.fillRect(0,0,width,height);
 68         g.setColor(reverse);
 69         g.drawString(randomString,18,20);
 70         
 71         for(int i = 0,n = random.nextInt(100); i< n;i++)
 72         {
 73             g.drawRect(random.nextInt(width),random.nextInt(height),1,1);
 74         }
 75         
 76         ServletOutputStream out = response.getOutputStream();
 77         
 78         JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
 79         
 80         encoder.encode(bi);
 81         
 82         out.flush();
 83         
 84     }
 85 
 86     /**
 87      * The doPost method of the servlet. <br>
 88      *
 89      * This method is called when a form has its tag value method equals to post.
 90      * 
 91      * @param request the request send by the client to the server
 92      * @param response the response send by the server to the client
 93      * @throws ServletException if an error occurred
 94      * @throws IOException if an error occurred
 95 */
 96     public void doPost(HttpServletRequest request, HttpServletResponse response)
 97             throws ServletException, IOException {
 98         
 99     }
100 
101     /**
102      * Initialization of the servlet. <br>
103      *
104      * @throws ServletException if an error occurs
105 */
106     public void init() throws ServletException {
107         // Put your code here
108     }
109 
110     public static final char[] CHARS = {'2','3','4','5','6','7','8','9','A','B','C','D','E','F','G','H','J','K',
111         'L','M','N','P','Q','R','S','T','U','V','W','X','Y','Z'};
112     
113     public static Random random = new Random();
114     
115     public static String getRandomString()
116     {
117         StringBuffer buffer = new StringBuffer();
118         for(int i = 0;i < 6;i++)
119         {
120             buffer.append(CHARS[random.nextInt(CHARS.length)]);
121         }
122         
123         return buffer.toString();
124     }
125     
126     public static Color getRandomColor()
127     {
128         return new Color(random.nextInt(255),random.nextInt(255),random.nextInt(255));
129     }
130     
131     public static Color getReverseColor(Color c)
132     {
133         return new Color(255 - c.getRed(),255 - c.getGreen(),255-c.getBlue());
134     }
135     
136 }

 

 1 <script type="text/javascript">
 2 function reloadImage()
 3   {
 4      document.getElementById('btn').disabled = true;
 5      document.getElementById('identity').src='servlet/IndentityServlet?ts' + new Date().getTime();
 6   }
 7 </script>
 8 
 9 <img src="servlet/IdentityServlet" id="identity" onload="btn.disabled = false;"
10 
11 <input type="button" value="換張圖片" onclick="reloadImage()" id="btn" />