Servlet 驗證碼

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.imageio.stream.ImageOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 能動態產生圖形，並且輸出圖形的Servlet
 * 
 * @author WilliamRong
 * @version 1.0
 * 
 */
public class GenerateImageServlet extends HttpServlet {
	private static final long serialVersionUID = 760480418450678827L;

	/**
	 * 產生的圖像的寬度，單位爲像素。
	 */
	private final static int WIDTH = 260;

	/**
	 * 產生的圖像的高度，單位爲像素。
	 */
	private final static int HEIGHT = 60;

	public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
		// 設置輸出的內容的類型爲jpeg圖像
		response.setContentType("image/jpeg");
		OutputStream os = response.getOutputStream();
		createImage(os);
		os.close();
	}

	/**
	 * 繪製輸出整個圖形
	 */
	public void createImage(OutputStream os) throws IOException {
		// 創建一個BufferedIamge對象
		BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
		// 獲取的Graphics2D對象，通過這個對象完成繪圖
		Graphics2D g = image.createGraphics();
		// 繪製背景圖
		g.setColor(Color.white);
		g.fillRect(0, 0, WIDTH, HEIGHT);
		// 畫邊框
		g.setColor(Color.black);
		g.drawRect(0, 0, WIDTH - 1, HEIGHT - 1);
		// 設定字體
		g.setFont(new Font("Times New Roman", Font.PLAIN, 60));
		// 生成隨機類
		Random random = new Random();
		// 取隨機產生的6位數字
		for (int i = 0; i < 6; i++) {
			String rand = String.valueOf(random.nextInt(10));
			// 將隨機產生的數字顯示到圖象中
			g.drawString(rand, 40 * i + 20, 50);
		}

		// 生成圖像的輸出流
		ImageOutputStream ios = ImageIO.createImageOutputStream(os);
		ImageIO.write(image, "jpeg", ios);
		ios.close();
	}
}