java 验证码编写.java部分(用servlet编写的)

import java.awt.Color;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.omg.CORBA.portable.ValueOutputStream;

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;


public class CheckcodeServlet extends HttpServlet {
    public void service(HttpServletRequest request,HttpServletResponse response)throws ServletException,IOException{
           /**
            *1 设置服务器返回的格式jpg格式的图片
            * 常见的还有：text/html和text/xml
            * 
            */
        response.setContentType("image/jpeg");
        /*2  画图    BufferedImage内存映射对象*/
            BufferedImage image=new BufferedImage(80,20,BufferedImage.TYPE_INT_BGR);
        //获得随机数
            Random r=new Random();
            //获得画笔
            Graphics g=image.getGraphics();
            //设置背景颜色
            
            g.setColor(new Color(r.nextInt(255), r.nextInt(255), r.nextInt(255)));
            
            //填充背景颜色
            g.fillRect(0, 0, 80,20);
            //设置前景颜色
            g.setColor(new Color(0,0,0));
            //生成随机数99999
            String number=String.valueOf( r.nextInt(99999));
            //画到图片上
            g.drawString(number, 5, 15);
            
            /** 3 压缩图片并输出
             * 获得字节输出流，因为要输出的是图像压缩之后
             * 的字节数组，所以不能用pringwriter.
             * 
             */
            
            OutputStream os =response.getOutputStream();
            //将图片压缩，输出
            JPEGImageEncoder encoder=JPEGCodec.createJPEGEncoder(os);
            encoder.encode(image);
            
            
        
    }
}