checkimage.java

一本jsp自学教材

package test;

import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
import com.sun.image.codec.jpeg.*;
import java.awt.image.*;
import java.awt.*;
import javax.imageio.ImageIO;

public class CheckImage extends HttpServlet {
    ServletConfig config=null;                          
    private int Rsize;
    public void init(ServletConfig config)throws ServletException
     {
       super.init(config);      
       this.config=config;
       String isize=config.getInitParameter("Rsize");
       Rsize=Integer.parseInt(isize);
     }
    public void doGet(HttpServletRequest request,
                      HttpServletResponse response)
        throws IOException, ServletException
    {        
        response.setContentType("image/jpeg;charset=GBK");
        HttpSession session=request.getSession(true);
        try{
           response.setHeader("Pragma","No-cache");
           response.setHeader("Cache-Control","no-cache");
           response.setDateHeader("Expires", 0);
           // 创建图象的宽和高
           int width=15*Rsize;
           int height=20;
           BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);      
           Graphics g = image.getGraphics();
           //创建随机对象
           Random random = new Random();
           // 设置背景色
           g.setColor(getRandomColor(200,250));
           g.fillRect(0, 0, width, height); 

         // 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
         g.setColor(getRandomColor(160,200));
            for (int i=0;i<155;i++)
             {
               int x = random.nextInt(width);
               int y = random.nextInt(height);
               int xl = random.nextInt(12);
               int yl = random.nextInt(12);
               g.drawLine(x,y,x+xl,y+yl);
             }
         //设定字体
        Font ff=new Font("Monotype Corsiva",Font.PLAIN,20);
        g.setFont(ff);
        // 随机产生的认证码（每次产生一位）
        String sRand="";
        for (int i=0;i<Rsize;i++)
          {
            String rand=String.valueOf(random.nextInt(10));
            sRand+=rand;
                // 设置各数位的颜色
            g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
            g.drawString(rand,14*i+6,17);
         }
 
      session.setAttribute("rand",sRand);
      g.dispose();// 图象生效

      // 输出图象到页面
      ImageIO.write(image, "JPEG", response.getOutputStream());
       }  
     catch(Exception e)
          {
            PrintWriter out = response.getWriter();
            out.print(e.toString()); 
          }       
    } 
    //获取随机颜色
    Color getRandomColor(int c1,int c2)
      {  
        Random random = new Random();
        if(c1>255) 
          c1=255;
        if(c2>255) 
          c2=255;
        int b1=c1+random.nextInt(c2-c1);
        int b2=c1+random.nextInt(c2-c1);
        int b3=c1+random.nextInt(c2-c1);
        return new Color(b1,b2,b3);
      } 
    public void doPost(HttpServletRequest request,
                      HttpServletResponse response)
        throws IOException, ServletException
    {  
      doGet(request,response);    
    }   
   public void destroy()
    {
     config=null;
    }
}