java web开发之验证码

package web; 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 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 { System.out.println("service..."); //生成一个消息头content-type,告诉浏览器服务器 //返回的数据类型是一个jpg格式的图片。 response.setContentType("image/jpeg"); // 图片的内存映像 BufferedImage image = new BufferedImage(60, 20, BufferedImage.TYPE_INT_RGB); // 获得画笔对象 Random r = new Random(); Graphics g = image.getGraphics(); g.setColor( new Color(r.nextInt(255), r.nextInt(255), r.nextInt(255))); g.fillRect(0, 0, 60, 20); g.setColor(new Color(0,0,0)); String number = String.valueOf( r.nextInt(99999)); g.drawString(number, 5, 15); g.drawLine(r.nextInt(60),r.nextInt(20), r.nextInt(60),r.nextInt(20)); g.drawLine(r.nextInt(60),r.nextInt(20), r.nextInt(60),r.nextInt(20)); g.drawLine(r.nextInt(60),r.nextInt(20), r.nextInt(60),r.nextInt(20)); g.drawLine(r.nextInt(60),r.nextInt(20), r.nextInt(60),r.nextInt(20)); // 压缩成jpeg格式 OutputStream os = response.getOutputStream(); JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(os); // 把BufferedImage对象中的图像信息编码后 // 向创建该对象(encoder)时指定的输出流输出 encoder.encode(image); } }