JavaWeb网页上的验证码生成

简单生成网页上验证码，本例使用Servlet写的简例

package com.againfly.demo;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
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 CodeDemo extends HttpServlet {
    private int width = 160;// 图片的宽度。
    private int height = 40;// 图片的高度。
    private int codeCount = 4;// 验证码字符个数
    private int lineCount = 20;// 验证码干扰线数
    Random random = new Random();
    
    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
    	response.setContentType("image/png");
        response.setHeader("Pragma", "no-cache");//禁止图像缓存。
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expires", 0);
        
        String code = genCode(codeCount);
        ImageIO.write(creatImage(code), "png", response.getOutputStream());
    }
    
    private BufferedImage creatImage(String code) {
        int fontWidth = width / codeCount;// 字体的宽度
        int fontHeight = height - 5;// 字体的高度
        int codeY = height - 8;

        // 图像buffer
        BufferedImage buffImg = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        Graphics g = buffImg.getGraphics();
       
        g.setColor(getRandColor(200, 250));	// 设置背景色
        g.fillRect(0, 0, width, height);

        // 设置干扰线
        for (int i = 0; i < lineCount; i++) {
            int xs = random.nextInt(width);
            int ys = random.nextInt(height);
            int xe = xs + random.nextInt(width);
            int ye = ys + random.nextInt(height);
            g.setColor(getRandColor(1, 255));
            g.drawLine(xs, ys, xe, ye);
        }

        // 添加噪点
        float yawpRate = 0.01f;// 噪声率
        int area = (int) (yawpRate * width * height);
        for (int i = 0; i < area; i++) {
            int x = random.nextInt(width);
            int y = random.nextInt(height);
            buffImg.setRGB(x, y, random.nextInt(255));
        }

        for(int i = 0 ; i < code.length(); i++){
        	g.setColor(getRandColor(1, 255));
        	g.setFont(getFont(fontHeight));
        	g.drawString(code.charAt(i) + "", i * fontWidth + 3, codeY);
        }
        return buffImg;
    }
	
	// 得到随机字符
    private String genCode(int n) {
		String s = "ABCDEFGHJKLMNPRSTUVWXYZ0123456789";
		StringBuilder builder = new StringBuilder();
		for (int i = 0; i < n; i++) {				//验证码长度
			builder.append((char) s.charAt(random.nextInt(s.length())));
		}
		return builder.toString();
    }
    
    //得到随机颜色
    private Color getRandColor(int fc, int bc) {// 给定范围获得随机颜色
        if (fc > 255)	fc = 255;
        if (fc < 0)	fc = 0;
        if (bc > 255)	bc = 255;
        if (bc < 0)	bc = 0;
        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);
    }
    
    //随机字体
    private Font getFont(int size) {
        Random random = new Random();
        Font font[] = new Font[5];
        font[0] = new Font("Ravie", Font.PLAIN, size);
        font[1] = new Font("Antique Olive Compact", Font.PLAIN, size);
        font[2] = new Font("Fixedsys", Font.PLAIN, size);
        font[3] = new Font("Wide Latin", Font.PLAIN, size);
        font[4] = new Font("Gill Sans Ultra Bold", Font.PLAIN, size);
        return font[random.nextInt(5)];
    }
}

显示效果如下：