利用java自动生成验证码

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.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import org.apache.struts2.ServletActionContext;
public class CodeUtil {
    private HttpServletRequest request;
    private HttpServletResponse response;
    private int imgWidth = 0;//验证码图片的宽度
    private int imgHeight = 0;//验证码图片的高度
    private int codeCount = 0;//验证码的个数
    private int x = 0;
    private int fontHeight;
    private int codeY;
    private String fontStyle;
    private static final long serialVersionUID = 128554012633034503L;
    public CodeUtil(){
    	init();
		try {
			response = ServletActionContext.getResponse();
			request = ServletActionContext.getRequest();
			response.setCharacterEncoding("UTF-8");
			request.setCharacterEncoding("UTF-8");
			response.setContentType("text/html;charset=UTF-8");
		} catch (Exception e) {
			e.printStackTrace();
		}	
    }
    /**
     * 初始化配置参数
     */
    public void init(){
        // 宽度
        String strWidth = "60";
        // 高度
        String strHeight ="20";
        // 字符个数
        String strCodeCount = "4";
 
        fontStyle = "Times New Roman";
 
        // 将配置的信息转换成数值
        try {
            if (strWidth != null && strWidth.length() != 0) {
                imgWidth = Integer.parseInt(strWidth);
            }
            if (strHeight != null && strHeight.length() != 0) {
                imgHeight = Integer.parseInt(strHeight);
            }
            if (strCodeCount != null && strCodeCount.length() != 0) {
                codeCount = Integer.parseInt(strCodeCount);
            }
        } catch (NumberFormatException e) {
            e.printStackTrace();
        }
 
        x = imgWidth / (codeCount + 1);
        fontHeight = imgHeight - 2;
        codeY = imgHeight - 12;
    }
 
    /**
     * 
     * @param request
     * @param response
     * @throws ServletException
     * @throws IOException
     */
    public void processRequest(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("image/jpg");
        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
        BufferedImage image = new BufferedImage(imgWidth, imgHeight,
                BufferedImage.TYPE_INT_RGB);
 
        // 获取图形上下文
        Graphics2D g = image.createGraphics();
 
        // 生成随机类
        Random random = new Random();
 
        // 设定背景色
        g.setColor(Color.WHITE);
        g.fillRect(0, 0, imgWidth, imgHeight);
 
        // 设定字体
        g.setFont(new Font(fontStyle, Font.PLAIN + Font.ITALIC, fontHeight));
 
        // 画边框
        g.setColor(new Color(55, 55, 12));
        g.drawRect(0, 0, imgWidth - 1, imgHeight - 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 < 160; i++) {
//            int x = random.nextInt(imgWidth);
//            int y = random.nextInt(imgHeight);
//            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 = "";
        int red = 0, green = 0, blue = 0;
        for (int i = 0; i < codeCount; i++) {
            red = random.nextInt(255);
            green = random.nextInt(255);
            blue = random.nextInt(255);
            int wordType = random.nextInt(3);
            char retWord = 0;
            switch (wordType) {
            case 0:
                retWord = this.getSingleNumberChar();
                break;
            case 1:
                retWord = this.getLowerOrUpperChar(0);
                break;
            case 2:
                retWord = this.getLowerOrUpperChar(1);
                break;
            }
            sRand += String.valueOf(retWord);
            g.setColor(new Color(red, green, blue));
            g.drawString(String.valueOf(retWord), (i) * x+5, codeY+7);//这个地方非常重要，关系到验证码是否居中显示。要根据大小进行调整。
        }
        // 将认证码存入SESSION
        sRand=sRand.toLowerCase();
        session.setAttribute("rand", sRand);
        // 图象生效
        g.dispose();
        ServletOutputStream responseOutputStream = response.getOutputStream();
        // 输出图象到页面
		ImageIO.write(image, "JPG", 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);
    }
    
    private char getSingleNumberChar() {
        Random random = new Random();
        int numberResult = random.nextInt(10);
        int ret = numberResult + 48;
        return (char) ret;
    }
 
    private char getLowerOrUpperChar(int upper) {
        Random random = new Random();
        int numberResult = random.nextInt(26);
        int ret = 0;
        if (upper == 0) {// 小写
            ret = numberResult + 97;
        } else if (upper == 1) {// 大写
            ret = numberResult + 65;
        }
        return (char) ret;
    }
    public void execute(){//程序执行的路口
    	try {
		processRequest(request,response);
		} catch (Exception e) {			
			e.printStackTrace();
		} 
    }
}