用servlet实现验证码功能

package accp.test.servlet; import java.awt.Color; import java.awt.Font; import java.awt.Graphics2D; import java.awt.image.BufferedImage; import java.io.IOException; import java.util.Random; import javax.imageio.ImageIO; import javax.servlet.ServletException; import javax.servlet.ServletOutputStream; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; public class RandomCodeServlet extends HttpServlet { /** * */ private static final long serialVersionUID = -4233448556545944091L; //验证码图片的宽度和高度 private int width=60; private int height=20; /** * Constructor of the object. */ public RandomCodeServlet() { super(); } /** * Destruction of the servlet. <br> */ public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } /** * 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 void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { BufferedImage buffImg=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB); Graphics2D g=buffImg.createGraphics(); Random random=new Random(); g.setColor(Color.WHITE); g.fillRect(0, 0, width, height); Font font=new Font("Times New Roman",Font.PLAIN,18); g.setFont(font); //画边框 g.setColor(Color.BLACK); g.drawRect(0, 0, width-1, height-1); //随机长生160条干扰线，防止被其他程序探测到 g.setColor(Color.GRAY); for(int i=0;i<160;i++){ int x=random.nextInt(width); int y=random.nextInt(height); int x1=random.nextInt(12); int y1=random.nextInt(12); g.drawLine(x, y, x+x1, y+y1); } StringBuffer randomCode=new StringBuffer(); int red=0,green=0,blue=0; //随机产生4位验证码 for (int i = 0; i < 4; i++) { String strRand=String.valueOf(random.nextInt(10)); red=random.nextInt(110); green=random.nextInt(50); blue=random.nextInt(50); g.setColor(new Color(red,green,blue)); g.drawString(strRand, 13*i+6, 16); randomCode.append(strRand); } //将4位数字的验证码保存到Session中 HttpSession session=request.getSession(); session.setAttribute("randomCode", randomCode.toString()); //静止图像缓存 response.setHeader("Pragma", "no-cache"); response.setHeader("Cache-Control", "no-cache"); response.setDateHeader("Expires",0); response.setContentType("image/jpeg"); ServletOutputStream sos=response.getOutputStream(); ImageIO.write(buffImg, "jpeg", sos); sos.close(); } /** * The doPost method of the servlet. <br> * * This method is called when a form has its tag value method equals to post. * * @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 void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } /** * Initialization of the servlet. <br> * * @throws ServletException if an error occurs */ public void init() throws ServletException { // Put your code here } }