验证码

 原创链接：http://www.cnblogs.com/yanqin/p/5345037.html （允许转载，但请注明原创链接） 

package com.me.util;

import java.awt.BasicStroke;
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.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


public class VerifyCodeServlet extends HttpServlet {

	
	private static final long serialVersionUID = 1L;

	@Override
	public void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		//画图
		BufferedImage img = getImage();
		//输出
		output(img, resp.getOutputStream());
		//将验证码存到session
		req.getSession().setAttribute("vCode",text);
	}
	
	
	private int w = 120;
	private int h = 40;
 	private Random r = new Random();
 	// {"宋体", "华文楷体", "黑体", "华文新魏", "华文隶书", "微软雅黑", "楷体_GB2312"}
	private String[] fontNames  = {"宋体", "华文楷体", "黑体", "微软雅黑", "楷体_GB2312"};
	private String codes  = "23456789abcdefghjkmnopqrstuvwxyzABCDEFGHJKMNPQRSTUVWXYZ";
	//背景色
	private Color bgColor  = new Color(255, 255, 255);
	private String text ;
	
	//字体颜色
	private Color randomColor () {
		int red = r.nextInt(150);
		int green = r.nextInt(150);
		int blue = r.nextInt(150);
		return new Color(red, green, blue);
	}
	
	//字体
	private Font randomFont () {
		int index = r.nextInt(fontNames.length);
		String fontName = fontNames[index];
		int size = r.nextInt(4) + 32; 
		return new Font(fontName, Font.PLAIN, size);
	}
	
	//画线
	private void drawLine (BufferedImage image) {
		int num  = 3;
		Graphics2D g2 = (Graphics2D)image.getGraphics();
		for(int i = 0; i < num; i++) {
			int x1 = r.nextInt(w);
			int y1 = r.nextInt(h);
			int x2 = r.nextInt(w);
			int y2 = r.nextInt(h); 
			g2.setStroke(new BasicStroke(1.5F)); 
			g2.setColor(new Color(200,200,200)); 
			g2.drawLine(x1, y1, x2, y2);
		}
	}
	
	//随机字
	private char randomChar () {
		int index = r.nextInt(codes.length());
		return codes.charAt(index);
	}
	
	//画背景
	private BufferedImage createImage () {
		BufferedImage image = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB); 
		Graphics2D g2 = (Graphics2D)image.getGraphics(); 
		g2.setColor(this.bgColor);
		g2.fillRect(0, 0, w, h);
 		return image;
	}
	
	//绘画
	private BufferedImage getImage () {
		BufferedImage image = createImage(); 
		Graphics2D g2 = (Graphics2D)image.getGraphics();
		StringBuilder sb = new StringBuilder();
		// 向图片中画4个字符
		for(int i = 0; i < 4; i++)  {
			String s = randomChar() + ""; 
			sb.append(s); 
			float x = i * w / 5 + 12; 
			g2.setColor(randomColor());
			g2.setFont(randomFont());
			g2.drawString(s, x, h-5);
		}
		this.text = sb.toString();
		drawLine(image);
		return image;
	}
	
	private static void output (BufferedImage image, OutputStream out) 
				throws IOException {
		ImageIO.write(image, "JPEG", out);
	}
	
}