Java的随机验证码生成类

package cn.edu.hbcit.util;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.imageio.stream.ImageOutputStream;
//闂呫劍顭奸弫鎼侇敚
public class RandomNumUtil {
	private ByteArrayInputStream image;// 閸ユ儳鍎�
	private String str;// 妤犲矁鐦夐惍锟�

	private RandomNumUtil() {
		init();// 閸掓繂顬婇崠鏍х潣閹拷
	}

	/*
	 * 閸欐牕绶盧andomNumUtil鐎圭偘绶�
	 */
	public static RandomNumUtil Instance() {
		return new RandomNumUtil();
	}

	/*
	 * 閸欐牕绶辨宀冪槈閻礁娴橀悧锟�
	 */
	public ByteArrayInputStream getImage() {
		return this.image;
	}

	/*
	 * 閸欐牕绶遍崶鍓у閻ㄥ嫰鐛欑拠浣虹垳()
	 */
	public String getString() {
		return this.str;
	}

	private void init() {
		// 閸︺劌鍞寸�妯硅厬閸掓稑缂撻崶鎹愯杽
		int width = 63, height = 20;
		BufferedImage image = new BufferedImage(width, height,
				BufferedImage.TYPE_INT_RGB);
		// 閼惧嘲褰囬崶鎯ц埌娑撳﹣绗呴弬锟�
		Graphics g = image.getGraphics();
		// 閻㈢喐鍨氶梾蹇旀簚缁拷
		Random random = new Random();
		// 鐠佹儳鐣鹃懗灞炬珯閼癸拷
		g.setColor(getRandColor(200, 250));
		g.fillRect(0, 0, width, height);
		// 鐠佹儳鐣剧�妞剧秼
		g.setFont(new Font("Times New Roman", Font.PLAIN, 18));
		// 闂呭繑婧�禍褏鏁�55閺夆�鍏遍幍鎵殠閿涘奔濞囬崶鎹愯杽娑擃厾娈戠拋銈堢槈閻椒绗夐弰鎾诡枂閸忚泛鐣犵粙瀣碍閹恒垺绁撮崚锟�
		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);
		}
		// 閸欐牠娈㈤張杞伴獓閻㈢喓娈戠拋銈堢槈閻拷6娴ｅ秵鏆熺�锟�
		String sRand = "";
		for (int i = 0; i < 4; i++) {
			String rand = String.valueOf(random.nextInt(10));
			sRand += rand;
			// 鐏忓棜顓荤拠浣虹垳閺勫墽銇氶崚鏉挎禈鐠炩�鑵�
			g.setColor(new Color(20 + random.nextInt(110), 20 + random
					.nextInt(110), 20 + random.nextInt(110)));
			// 鐠嬪啰鏁ら崙鑺ユ殶閸戠儤娼甸惃鍕杹閼硅尙娴夐崥宀嬬礉閸欘垵鍏橀弰顖氭礈娑撹櫣顬岀�鎰亰閹恒儴绻庨敍灞惧娴犮儱褰ч懗鐣屾纯閹恒儳鏁撻幋锟�
			g.drawString(rand, 13 * i + 6, 16);
		}
		// 鐠у锟芥宀冪槈閻拷
		this.str = sRand;

		// 閸ユ崘钖勯悽鐔告櫏
		g.dispose();
		ByteArrayInputStream input = null;
		ByteArrayOutputStream output = new ByteArrayOutputStream();
		try {
			ImageOutputStream imageOut = ImageIO
					.createImageOutputStream(output);
			ImageIO.write(image, "JPEG", imageOut);
			imageOut.close();
			input = new ByteArrayInputStream(output.toByteArray());
		} catch (Exception e) {
			System.out.println("妤犲矁鐦夐惍浣告禈閻楀洣楠囬悽鐔峰毉閻滀即鏁婄拠顖ょ窗" + e.toString());
		}

		this.image = input;/* 鐠у锟介崶鎯у剼 */
	}

	/*
	 * 缂佹瑥鐣鹃懠鍐ㄦ纯閼惧嘲绶遍梾蹇旀簚妫版粏澹�
	 */
	private 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);
	}
}