Java实现图片验证码，点击刷新图片验证码

创建生成图片验证码的工具类：

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;

/**
 * 验证码生成器
 * 
 */
public class SCaptcha {
    // 图片的宽度。
    private int width = 120;
    // 图片的高度。
    private int height = 40;
    // 验证码字符个数
    private int codeCount = 4;
    // 验证码干扰线数
    private int lineCount = 50;
    // 验证码
    private String code = null;
    // 验证码图片Buffer
    private BufferedImage buffImg = null;
	// 随即的字符数组
    private char[] codeSequence = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'M', 'N', 'P', 'Q', 'R',
            'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', '2', '3', '4', '5', '6', '7', '8', '9' };
    // 生成随机数
    private Random random = new Random();

    public SCaptcha() {
        this.createCode();
    }

    /**
     * 
     * @param width 图片宽
     * @param height 图片高
     */
    public SCaptcha(int width, int height) {
        this.width = width;
        this.height = height;
        this.createCode();
    }

    /**
     * 
     * @param width 图片宽
     * @param height 图片高
     * @param codeCount 字符个数
     * @param lineCount 干扰线条数
     */
    public SCaptcha(int width, int height, int codeCount, int lineCount) {
        this.width = width;
        this.height = height;
        this.codeCount = codeCount;
        this.lineCount = lineCount;
        this.createCode();
    }

    public void createCode() {
        int codeX = 0;
        int fontHeight = 0;
        fontHeight = height - 5;// 字体的高度
        codeX = width / (codeCount + 3);// 每个字符的宽度

        // 图像buffer
        buffImg = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        Graphics2D g = buffImg.createGraphics();

        // 将图像填充为白色
        g.setColor(Color.WHITE);
        g.fillRect(0, 0, width, height);

        // 创建字体
        ImgFontByte imgFont = new ImgFontByte();
        Font font = imgFont.getFont(fontHeight);
        g.setFont(font);

        StringBuffer randomCode = new StringBuffer();
        // 随机产生验证码字符
        for (int i = 0; i < codeCount; i++) {
            String strRand = String.valueOf(codeSequence[random.nextInt(codeSequence.length)]);
            // 设置字体颜色
            g.setColor(getRandomColor());
            // 设置字体位置
            g.drawString(strRand, (i + 1) * codeX, getRandomNumber(height / 2) + 25);
            randomCode.append(strRand);
        }
        code = randomCode.toString();
    }

    /** 获取随机颜色 */
    private Color getRandomColor() {
        int r = getRandomNumber(255);
        int g = getRandomNumber(255);
        int b = getRandomNumber(255);
        return new Color(r, g, b);
    }

    /** 获取随机数 */
    private int getRandomNumber(int number) {
        return random.nextInt(number);
    }

    public void write(String path) throws IOException {
        OutputStream sos = new FileOutputStream(path);
        this.write(sos);
    }

    public void write(OutputStream sos) throws IOException {
        ImageIO.write(buffImg, "png", sos);
        sos.close();
    }

    public BufferedImage getBuffImg() {
        return buffImg;
    }

    public String getCode() {
        return code;
    }

    /** 字体样式类 */
    class ImgFontByte {
        public Font getFont(int fontHeight) {
            try {
                Font baseFont = Font.createFont(Font.HANGING_BASELINE, new ByteArrayInputStream(
                        hex2byte(getFontByteStr())));
                return baseFont.deriveFont(Font.PLAIN, fontHeight);
            } catch (Exception e) {
                return new Font("Arial", Font.PLAIN, fontHeight);
            }
        }

        private byte[] hex2byte(String str) {
            if (str == null)
                return null;
            str = str.trim();
            int len = str.length();
            if (len == 0 || len % 2 == 1)
                return null;

            byte[] b = new byte[len / 2];
            try {
                for (int i = 0; i < str.length(); i += 2) {
                    b[i / 2] = (byte) Integer.decode("0x" + str.substring(i, i + 2)).intValue();
                }
                return b;
            } catch (Exception e) {
                return null;
            }
        }

        // 字体文件的十六进制字符串
        private String getFontByteStr() {
            //防止报字符串长度过长错误，改为从配置文件读取
            return ReadFontByteProperties.getFontByteStr();
        }
    }
}

controller层代码：

		// 设置响应的类型格式为图片格式
        response.setContentType("image/jpeg");
        // 禁止图像缓存。
        response.setHeader("Pragma", "no-cache");
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expires", 0);
        //实例生成验证码对象
        SCaptcha instance = new SCaptcha();
        //将验证码存入session
        request.getSession().setAttribute("verification", instance.getCode());
        //向页面输出验证码图片
        instance.write(response.getOutputStream());

页面代码：

效果如下：

如果想实现点击刷新图片，则将页面代码改至如下：

添加js代码：

		function changeCodeImg(){
	　　	var num=Math.ceil(Math.random()*10);//生成一个随机数（防止缓存）
			var src = $("#vimg")[0].src; 
			//alert(src + "?num=" + num);
			$("#vimg").attr('src',src + "?num=" + num); 
	　　}

这样就OK了。

补一下ReadFontByteProperties代码：

import java.io.InputStream;
import java.util.Properties;

/**
 * 读取文件字体类
 * @author QQ
 *
 */
public class ReadFontByteProperties {
     
    static private String fontByteStr = null;
    static {
     
        loads();
    }
    synchronized static public void loads() {
     
        if (fontByteStr == null) {
     
            InputStream is = ReadFontByteProperties.class.getResourceAsStream("/fontByte.properties");
            Properties dbproperties = new Properties();
            try {
     
                dbproperties.load(is);
                fontByteStr = dbproperties.getProperty("fontByteStr").toString();
            } catch (Exception e) {
     
                //System.err.println("读取失败！请确保fontByte.properties在CLASSPATH指定的路径中");
            }
        }
    }
    public static String getFontByteStr() {
     
        if (fontByteStr == null)
            loads();
        return fontByteStr;
    }
}