java后台验证码的生成

前台代码：

<tr>
	<td>验证码</td>
	<td><input name="checkCode" type="text" id="checkCode" /></td>
	<td><img src="CheckCode.do" id="ValidateImage" onClick="refresh()" title="点击换一张" style="cursor: pointer;" /></td>
</tr>

后台java代码：

public class CheckCodeAction {
	private ByteArrayInputStream inputStream;	
 
	public void setInputStream(ByteArrayInputStream inputStream) {
		this.inputStream = inputStream;
	}
	public ByteArrayInputStream getInputStream() {
		return inputStream;
	}

	public String execute() throws Exception {
		// 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60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 < 60; 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 rand,sRand = "" ;
		
		for (int i = 0; i < 4; i++) {
			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
		HttpSession session = this.getSession();
		session.setAttribute("rand", sRand); 
		System.out.println(sRand);
		// 图象生效
		g.dispose();
		ByteArrayOutputStream output = new ByteArrayOutputStream();
		ImageOutputStream imageOut = ImageIO.createImageOutputStream(output);
		ImageIO.write(image, "JPEG", imageOut);
		imageOut.close();
		ByteArrayInputStream input = new ByteArrayInputStream(output.toByteArray());
		this.setInputStream(input);
		return SUCCESS;
	}

	/*
	 * 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);
	}

}

配置文件：

 <action name="CheckCode" class = "CheckCodeAction">
      <result type= "stream">
       	　　<param name="contentType">image/jpeg</param>
       	　　<param name="inputName">inputStream</param>
      </result>
 </action>