Servlet里写验证码

public class CodeServlet extends HttpServlet {

/**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

response.setContentType("image/jpeg");

// 创建图片缓冲流
int width = 90; // 宽度
int height = 25; // 高度
int imageType = BufferedImage.TYPE_INT_RGB; // 颜色
BufferedImage image = new BufferedImage(width, height, imageType);

// 获取缓冲图片流中的画布
Graphics g = image.getGraphics();
// 设置画笔的颜色
g.setColor(Color.lightGray);
// 填充画布区域
g.fillRect(0, 0, width, height);

// 输出的内容
String word = "abcdefhijklmnopqrstuvwxyz";
// 将要输出的内容，转换为 字节数组
char[] words = word.toCharArray();

// 定义一个随机对象
Random random = new Random();

String sessionWord = "";

for (int i = 0; i < 4; i++) {
String temp = words[random.nextInt(words.length)] + "";

sessionWord += temp;
// 更改画笔的颜色
g.setColor(new Color(random.nextInt(255), random.nextInt(255),
random.nextInt(255)));
g.setFont(new Font("微软雅黑", Font.BOLD, 20));
// 使用画笔，在画布上写字
g.drawString(temp, 20 * i + 10, 20);
}

request.getSession().setAttribute("code", sessionWord);

// 获取servlet 输出流
OutputStream output = response.getOutputStream();
// 图片io流
ImageIO.write(image, "jpeg", output);

}

}