实现动态验证码
import java.awt.Color;import java.awt.Font;import java.awt.Graphics;import java.awt.image.BufferedImage;import java.io.IOException;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 AuthCodeServlet extends HttpServlet {private static final long serialVersionUID = 1L;private static final int W = 60;private static final int H = 25;private static final String[] CTable = ("1 2 3 4 5 6 7 8 9 " + "A B C D E F G H I J K L M N O P Q R S T U V W X Y Z").split(" ");@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {BufferedImage img = new BufferedImage(W, H, BufferedImage.TYPE_INT_RGB);Graphics g = img.getGraphics();// 画背景g.setColor(Color.PINK);g.fillRect(0, 0, img.getWidth(), img.getHeight());// 画干扰线g.setColor(Color.GRAY);for (int i = 0; i < 20; i++) {g.drawLine(new Random().nextInt(W), new Random().nextInt(H), new Random().nextInt(W), new Random().nextInt(H));}// 随机生成四个数g.setColor(Color.BLUE);g.setFont(new Font("Courier New", Font.BOLD, 16));for (int i = 0; i < 4; i++) {g.drawString(CTable[new Random().nextInt(35)], 6 + i * 13, 17);}// 向客户端输出resp.setContentType("image/jpeg");JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(resp.getOutputStream());encoder.encode(img);}}