Java实现验证码图片

这样的实现方式对JDK版本有要求。
 1 package edu.cloud.editmap.utils;

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

import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

public class IdentityCode {
    private static final long serialVersionUID = -479885884254942306L;

    public static final char[] CHARS = { '2', '3', '4', '5', '6', '7', '8',
            '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'J', 'K', 'L', 'M',
            'N', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' };

    public static Random random = new Random();

    public static String getRandomString() {
        StringBuffer buffer = new StringBuffer();
        for (int i = 0; i < 4; i++) {
            buffer.append(CHARS[random.nextInt(CHARS.length)]);
        }
        return buffer.toString();
    }

    public static Color getRandomColor() {
        return new Color(random.nextInt(255), random.nextInt(255), random
                .nextInt(255));
    }

    public static Color getReverseColor(Color c) {
        return new Color(255 - c.getRed(), 255 - c.getGreen(), 255 - c
                .getBlue());
    }

    public static void createImage(HttpServletResponse response,HttpServletRequest request){


        response.setContentType("image/jpeg");
        
        String randomString = getRandomString();
        System.out.println(randomString);
        
        request.getSession().setAttribute("indentity_code", randomString);
        
        int width = 100;
        int height = 30;

        Color color = getRandomColor();
        Color reverse = getReverseColor(color);

        BufferedImage bi = new BufferedImage(width, height,
                BufferedImage.TYPE_INT_RGB);
        Graphics2D g = bi.createGraphics();
        g.setFont(new Font(Font.SANS_SERIF, Font.BOLD, 16));
        g.setColor(color);
        g.fillRect(0, 0, width, height);
        g.setColor(reverse);
        g.drawString(randomString, 18, 20);
        for (int i = 0, n = random.nextInt(100); i < n; i++) {
            g.drawRect(random.nextInt(width), random.nextInt(height), 1, 1);
        }
        
        // 转成JPEG格式
        try {
            
            ServletOutputStream out = response.getOutputStream();
            JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
            encoder.encode(bi);
            out.flush();
            
        } catch (IOException e) {
            e.printStackTrace();
        }
        
    }

}