随机验证码（可刷新）

import java.io.IOException; import java.io.PrintWriter; import javax.imageio.ImageIO; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; 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.ServletOutputStream; 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 ImageServlet extends HttpServlet { /** * The doGet method of the servlet. <br> * * This method is called when a form has its tag value method equals to get. * * @param request * the request send by the client to the server * @param response * the response send by the server to the client * @throws ServletException * if an error occurred * @throws IOException * if an error occurred */ public char[] getRand() { char[] rand = new char[4]; String str = "0123456789qwertyuioplkjhgfdsazxcvbnmQWERTYUIOPLKJHGFDSAZXCVBNM"; for (int i = 0; i < 4; i++) { Random rd = new Random(); int index = rd.nextInt(str.length()); // 通过下标获取字符 rand[i] = str.charAt(index); } return rand; } public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // 接收图片类型 response.setContentType("image/jepg"); // 创建字节流 ServletOutputStream sos = response.getOutputStream(); // 设置缓冲区 BufferedImage img = null; img=new BufferedImage(60, 25, 4); // 在缓冲区中绘图 Graphics g = img.getGraphics(); // 调方法，得到随机字符 char[] rand = this.getRand(); // 保存于session中，以便其它页面可用 request.getSession().setAttribute("rand", new String(rand)); // 干拢线 g.setColor(Color.red); g.drawLine(new Random().nextInt(60), new Random().nextInt(60), new Random().nextInt(20), new Random().nextInt(20)); g.drawLine(new Random().nextInt(60), new Random().nextInt(60), new Random().nextInt(60), new Random().nextInt(20)); g.drawLine(new Random().nextInt(80), new Random().nextInt(60), new Random().nextInt(50), new Random().nextInt(20)); // 画背景色 g.drawRect(0, 0, 60, 25); g.setColor(Color.blue); // 设置前景色 g.setColor(Color.green); g.setFont(new Font("宋体",Font.BOLD+Font.ITALIC,18));//设置字体 g.drawString("" + rand[0], 6, 20); g.drawString("" + rand[1], 20, 15); g.drawString("" + rand[2], 30, 15); g.drawString("" + rand[3], 50, 20); // 关闭 g.dispose(); //JPEGImageEncoder code = JPEGCodec.createJPEGEncoder(sos); //code.encode(img); ImageIO.write((BufferedImage) img, "JPEG", sos); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req, resp); } }