Java生成验证码

// 前台页面
<input id="ver_code" name="ver_code" type="text" placeholder="输入验证码" />

<div>
<img src="<%=base%>user/checkCode?r=<%=System.currentTimeMillis() %>" id='verifyCode' />
</div>
<a href="javascript:void(0);" onclick="javaScript:changeV();">换一张</a>
<script type="text/javascript">
function changeV(){
document.getElementById("verifyCode").src="<%=base%>user/checkCode?r="+Math.random();
}
</script>

// 后台Java

public void checkCode(HttpServletRequest request, HttpServletResponse response) throws IOException{

// 设置页面不缓存

response.setHeader("Pragma", "No-cache");

response.setHeader("Cache-Control", "no-cache");

response.setDateHeader("Expires", 0);

response.setContentType("image/jpeg");

response.setCharacterEncoding("UTF-8");

// 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
// 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.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));
g.drawString(rand, 13 * i + 6, 16);
}

// 将认证码存入SESSION
request.getSession().setAttribute("verifyCode", sRand);

// 图象生效
g.dispose();

// 输出图象到页面
ServletOutputStream responseOutputStream = response.getOutputStream();
ImageIO.write(image, "JPEG", responseOutputStream);
// 以下关闭输入流！
responseOutputStream.flush();
responseOutputStream.close();

}