java生成验证码

package com.cqa.action.admin.login; 

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.imageio.ImageIO; 
import javax.servlet.ServletException; 
import javax.servlet.ServletOutputStream; 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 
import javax.servlet.http.HttpSession; 

import org.apache.struts2.ServletActionContext; 

import com.opensymphony.xwork2.ActionSupport; 

/** 
* 
* @author http://www.tot.name 
* @version 
*/ 
public class ValidateImageAction extends ActionSupport { 

/** 
* Processes requests for both HTTP <code>GET</code> and <code>POST</code> 
* methods. 
* 
* @param request 
*            servlet request 
* @param response 
*            servlet response 
*/ 
public void makeImage() throws ServletException, IOException { 
HttpServletRequest request = ServletActionContext.getRequest(); 
HttpServletResponse response = ServletActionContext.getResponse(); 
response.setContentType("image/jpeg"); 
response.setHeader("Pragma", "No-cache"); 
response.setHeader("Cache-Control", "no-cache"); 
response.setDateHeader("Expires", 0); 
HttpSession session = request.getSession(); 
// 在内存中创建图象 
int width = 60, height = 20; 
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); 

// 获取图形上下文 
Graphics g = image.getGraphics(); 

// 生成随机类 
Random random = new Random(); 

// 设定背景色 
g.setColor(getRandColor(200, 250)); 
g.fillRect(0, 0, width, height); 

// 设定字体 
g.setFont(new Font("Times New Roman", Font.PLAIN, 18)); 

// 画边框 
// g.setColor(new Color()); 
// g.drawRect(0,0,width-1,height-1); 

// 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到 
g.setColor(getRandColor(160, 200)); 
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); 
} 

// 取随机产生的认证码(4位数字) 
String sRand = ""; 
for (int i = 0; i < 4; i++) { 
String rand = String.valueOf(random.nextInt(10)); 
sRand += rand; 
// 将认证码显示到图象中 
g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));// 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成 
g.drawString(rand, 13 * i + 6, 16); 
} 

// 将认证码存入SESSION 
session.setAttribute("rand", sRand); 
// 图象生效 
g.dispose(); 
ServletOutputStream responseOutputStream = response.getOutputStream(); 
// 输出图象到页面 
ImageIO.write(image, "JPEG", responseOutputStream); 

// 以下关闭输入流！ 
responseOutputStream.flush(); 
responseOutputStream.close(); 
} 

Color getRandColor(int fc, int bc) {// 给定范围获得随机颜色 
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); 
} 

}