jsp页面验证码完整实例

package com.servlet; import java.awt.Color; import java.awt.Font; import java.awt.Graphics2D; import java.awt.image.BufferedImage; import java.io.IOException; import java.io.PrintWriter; 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 IdentityServlet extends HttpServlet { public static final char[] chars={'2','3','4','5','6','7','8','9','A'};//自定义验证码池 public static Random random=new Random();　　//随机数 public static String getRandomString(){　　//获取6位随机数，放在图片里 StringBuffer buffer=new StringBuffer(); for(int i=0;i<6;i++){ buffer.append(chars[random.nextInt(chars.length)]); } return buffer.toString(); } public static Color getRandomColor(){　　//获取随机的颜色 return new Color(random.nextInt(255), random.nextInt(255), random.nextInt(255)); } public static Color getReverseColor(Color c){　　//返回某颜色的反色 return new Color(255 - c.getRed(), 255 - c.getGreen(), 255 - c.getBlue()); } /** * Constructor of the object. */ public IdentityServlet() { super(); } /** * Destruction of the servlet. 
 */ public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } /** * The doGet method of the servlet. 
 * * 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 { response.setContentType("image/jpeg");　　//设置输出类型 String randomString = getRandomString();　　//随机字符串 request.getSession(true).setAttribute("randomString", randomString);//放到session里 int width=100;　　//图片宽度 int height=30;　　//图片高度 Color color=getRandomColor();　　//随机颜色，用于背景色 Color reverse=getReverseColor(color);//反色，用于前景色 //创建一个彩色图片 BufferedImage bi=new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); Graphics2D g=bi.createGraphics();　　//绘图对象 g.setFont(new Font(Font.SANS_SERIF,Font.BOLD,16));//设置字体 g.setColor(color);//设置颜色 g.fillRect(0, 0, width, height);//绘制背景 g.setColor(reverse); g.drawString(randomString, 18, 20);//绘制随机字符 for(int i=0,n=random.nextInt(100);i * * 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. 
 * * @throws ServletException if an error occurs */ public void init() throws ServletException { // Put your code here } }

    IdentityServlet com.servlet.IdentityServlet   IdentityServlet /servlet/IdentityServlet   index.jsp