登录验证码的实现

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;

public class ImageCodeUtil {

	private ByteArrayInputStream image;// 图像
	private String str;// 验证码
	
	public ImageCodeUtil() {
		// TODO Auto-generated constructor stub
		this.init();
	}
	/*
	 * 取得ImageUtil实例
	 */
	public static ImageCodeUtil Instance() {
		return new ImageCodeUtil();
	}

	/*
	 * 取得验证码图片
	 */
	public ByteArrayInputStream getImage() {
		return this.image;
	}

	/*
	 * 取得图片的验证码
	 */
	public String getString() {
		return this.str;
	}
	
	private void init() {
		// 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));
		// 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);
		}
		// 赋值验证码
		this.str = sRand;

		// 图象生效
		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("验证码图片产生出现错误：" + e.toString());
		}

		this.image = input;/* 赋值图像 */
	}

	/*
	 * 给定范围获得随机颜色
	 */
	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);
	}
}

 生成验证码的类，调用方法：

public String imageCode() throws Exception{
		ImageCodeUtil imgcode = ImageCodeUtil.Instance();
		String navTurn = WebTools.getParameter(getRequest(), "navTurn");
		setAttributeInRequest("navTurn", navTurn);
		this.setInputStream(imgcode.getImage());// 取得带有随机字符串的图片
		ActionContext.getContext().getSession().put("adminLoginCode", imgcode.getString());// 取得随机字符串放入HttpSession
		return SUCCESS;
	}

 

前台调用如下：

<div><label for="">验证码：</label>
<input class="login-yzm" name="imageCode" type="text" />
<img src="${ctx}/back/Admin/imageCode.do"    onClick="this.src='${ctx}/back/Admin/imageCode.do?random='+Math.random()"/>
<span class="codeErrorMes" style="color: red;display: none;"></span></div>

  配置文件struts.xml 中需要添加：

<result name="success" type="stream">
				<param name="contentType">image/jpeg</param>
				<param name="inputName">inputStream</param>
			</result>