验证码例子
1.准备一个servelt类，里面是生成图片的代码
package com.rhcy.servlet;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class GetRandomCode extends HttpServlet {
??? /**
??? ?* Constructor of the object.
??? ?*/
??? public GetRandomCode() {
??? ??? super();
??? }
??? /**
??? ?* Destruction of the servlet. <br>
??? ?*/
??? public void destroy() {
??? ??? super.destroy(); // Just puts "destroy" string in log
??? ??? // Put your code here
??? }
??? public void doGet(HttpServletRequest request, HttpServletResponse response)
??? ??? ??? throws ServletException, IOException {
??? ??? System.out.println("success");
??? ??? //HttpSession session = request.getSession();
??? ??? int width = 60;
??? ??? int height = 20;
??? ??? BufferedImage image = new BufferedImage(width, height, 1);
??? ??? Graphics g = image.getGraphics();
??? ??? Random random = new Random();
??? ??? g.setColor(getRandColor(200, 250));
??? ??? g.fillRect(0, 0, width, height);
??? ??? g.setFont(new Font("Times New Roman", 0, 24));
??? ??? Color randomColor = getRandColor(160, 200);
??? ??? g.setColor(randomColor);
??? ??? for (int i = 0; i < 155; i++) {
??? ??? ??? int x = random.nextInt(width);
??? ??? ??? int y = random.nextInt(height);
??? ??? ??? int xl = random.nextInt(12);
??? ??? ??? int yl = random.nextInt(12);
??? ??? ??? g.drawLine(x, y, x + xl, y + yl);
??? ??? }
??? ??? String rand = "";
??? ??? String sRand = "";
??? ??? for (int i = 0; i < 4; i++) {
??? ??? ??? switch (random.nextInt(2)) {
??? ??? ??? case 0: {
??? ??? ??? ??? rand = String.valueOf(random.nextInt(10));
??? ??? ??? ??? sRand = sRand + rand;
??? ??? ??? ??? break;
??? ??? ??? }
??? ??? ??? case 1: {
??? ??? ??? ??? rand = String.valueOf((char) (97 +random.nextInt(26)));
??? ??? ??? ??? sRand = sRand + rand;
??? ??? ??? ??? break;
??? ??? ??? }
??? ??? ??? default:break;
??? ??? ??? }
??? ??? ??? g.setColor(new Color(20 + random.nextInt(110), 20 + random .nextInt(110), 20 +random.nextInt(110)));
??? ??? ??? g.drawString(rand, 13 * i +random.nextInt(8), 15 + random .nextInt(5));
???
??? ??? }
???
??? ??? System.out.println("验证数字"+sRand);
??? ??? request.setAttribute("session_seccodeverify", sRand);
??? ??? g.dispose();
??? ??? ImageIO.write(image, "PNG", response.getOutputStream());
??? }
??? Color getRandColor(int fc, int bc) {
??? ??? Random random = new Random();
??? ??? if (fc > 255) {
??? ??? ??? fc = 255;
??? ??? }
??? ??? if (bc > 255) {
??? ??? ??? bc = 255;
??? ??? }
??? ??? int r = fc + random.nextInt(bc - fc);
??? ??? int g = fc + random.nextInt(bc - fc);
??? ??? int b = fc + random.nextInt(bc - fc);
??? ??? return new Color(r, g, b);
??? }
??? public void doPost(HttpServletRequest request, HttpServletResponse response)
??? ??? ??? throws ServletException, IOException {
??? ??? doGet(request, response);
??? }
??? public void init() throws ServletException {
??? ??? // Put your code here
??? }
}
2.? 配置文件web。xml里配置servlet配置
? <servlet>
??? <servlet-name>GetRandomCode</servlet-name>
??? <servlet-class>com.rhcy.servlet.GetRandomCode</servlet-class>
? </servlet>
? <servlet-mapping>
??? <servlet-name>GetRandomCode</servlet-name>
??? <url-pattern>/GetRandomCode</url-pattern>
? </servlet-mapping>
3.? 页面代码如下
??? ??? <script type="text/javascript">
???
???
??? function loadimage(){
???
??? ??? ??? var radom = Math.random()
??? ??? ??? document.getElementById("randImage").src = "GetRandomCode?"+radom;
??? ???
??? ?? }
??? ?? function sub(){
??? ?? ??? ??? return;
??? ?? }
</script>
</tr>
??? ??? ??? ??? ??? <tr width="80" align="center">
??? ??? ??? ??? ??? <td>
??? ??? ??? ??? ??? ??? 验证码：
??? ??? ??? ??? ??? </td>
??? ??? ??? ??? ??? <td width="150">
??? ??? ??? ??? ??? ??? <input name="yanzhengimg" type="text" id="yanzhengimg" size="20" />
??? ??? ??? ??? ??? ???
??? ??? ??? ??? ??? </td>
??? ??? ??? ??? ??? <td><img alt="验证码事例" name="randImage" id="randImage" src="GetRandomCode" width="51" height="25" border="1" onClick="loadimage()" style="cursor:hand"></td>
??? ??? ??? ??? </tr>
