servlet图片验证码

第一，先建立一个servlet命名为IdentityServlet

package com.myweb.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.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 {/** *  */private static final long serialVersionUID = 104097266476284687L;public static final char[] CHARS = { '2', '3', '4', '5', '6', '7', '8','9', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'J', 'K', 'L', 'M','N', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' };public static Random random = new Random(); // 随机数public static String getRandomString() { // 获取六位随机数StringBuffer buffer = new StringBuffer(); // 字符串缓冲for (int i = 0; i < 6; i++) {buffer.append(CHARS[random.nextInt(CHARS.length)]); // 每次取一个随机字符}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());}public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setContentType("image/jpeg");String randomString = getRandomString(); // 随机字符串request.getSession(true).setAttribute("randomString", randomString); //放到sessionint width = 100;int height = 30;Color color = getRandomColor(); // 随机颜色，用于背景色Color reverse = getReverseColor(color); // 反色，用于前景色BufferedImage bi = new BufferedImage(width, height,BufferedImage.TYPE_INT_BGR);// 创建一个彩色照片Graphics2D g = bi.createGraphics();g.setFont(new Font(Font.SANS_SERIF,Font.BOLD,16));//设置字体g.setColor(reverse);g.drawString(randomString, 18, 20);for(int i =0,n=random.nextInt(100); i < n; i++){  //画最多100个噪音点g.drawRect(random.nextInt(width), random.nextInt(height), 1, 1);//随机噪音点s}                                            ServletOutputStream out= response.getOutputStream();JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);//编码器System.out.println(randomString);encoder.encode(bi);  //对图片进行编码out.flush();  //输出到客户端}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {}}

2，在web.xml里添加

<?xml version="1.0" encoding="UTF-8"?><web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="3.0" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee   http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">  <display-name />  <servlet>    <servlet-name>action</servlet-name>    <servlet-class>org.apache.struts.action.ActionServlet</servlet-class>    <init-param>      <param-name>config</param-name>      <param-value>/WEB-INF/struts-config.xml</param-value>    </init-param>    <init-param>      <param-name>debug</param-name>      <param-value>3</param-value>    </init-param>    <init-param>      <param-name>detail</param-name>      <param-value>3</param-value>    </init-param>    <load-on-startup>1</load-on-startup>  </servlet>  <servlet>    <servlet-name>IdentityServlet</servlet-name>    <servlet-class>com.myweb.servlet.IdentityServlet</servlet-class>  </servlet>  <servlet-mapping>    <servlet-name>action</servlet-name>    <url-pattern>*.do</url-pattern>  </servlet-mapping>   <servlet-mapping>    <servlet-name>IdentityServlet</servlet-name>    <url-pattern>/servlet/IdentityServlet</url-pattern>  </servlet-mapping>  <welcome-file-list>    <welcome-file>index.jsp</welcome-file>  </welcome-file-list></web-app>

3，建立一个jsp或者html文件，怎样都行

我建的是MyJsp.jsp文件 

代码如下：

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%><%String path = request.getContextPath();String basePath = request.getScheme() + "://"+ request.getServerName() + ":" + request.getServerPort()+ path + "/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><base href="<%=basePath%>"><title>My JSP 'MyJsp.jsp' starting page</title><meta http-equiv="pragma" content="no-cache"><meta http-equiv="cache-control" content="no-cache"><meta http-equiv="expires" content="0"><meta http-equiv="keywords" content="keyword1,keyword2,keyword3"><meta http-equiv="description" content="This is my page"><!--<link rel="stylesheet" type="text/css" href="styles.css">--><script>function reloadImage() {document.getElementById('btn'), disabled = true;document.getElementById('identity').src = 'servlet/IdentityServlet?ts='+ new Date().getTime();}</script></head><body><img src="servlet/IdentityServlet" id="identity"onload="btn.disabled=false;" /><input type="button" value="换个图片" onclick="reloadImage()" id="btn"><br></body></html>

然后成功了，截图如下：