import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.Serializable;
import java.util.Random;
import javax.imageio.ImageIO;
import org.apache.commons.lang3.RandomUtils;
import com.alibaba.druid.util.Base64;
/**
 *  
 * @ClassName: ValidateCodeUtil
 * @Description: 驗證碼生成工具類
 * @author chenhx
 * @date 2017年11月14日 上午11:00:07
 */
public class ValidateCodeUtil {  
    private static Validate validate = null;                  //驗證碼類，用于最后返回此對象，包含驗證碼圖片base64和真值
    private static Random random = new Random();              //隨機類，用于生成隨機參數(shù)
    private static String randString = "0123456789abcdefghijkmnpqrtyABCDEFGHIJLMNQRTY";//隨機生成字符串的取值范圍  
    private static int width = 80;     //圖片寬度  
    private static int height = 34;    //圖片高度  
    private static int StringNum = 4;  //字符的數(shù)量  
    private static int lineSize = 40;  //干擾線數(shù)量  
    //將構造函數(shù)私有化 禁止new創(chuàng)建
    private ValidateCodeUtil() {
		super();
	}
    /** 
     * 獲取隨機字符,并返回字符的String格式 
     * @param index (指定位置) 
     * @return 
     */  
    private static String getRandomChar(int index) {  
        //獲取指定位置index的字符，并轉換成字符串表示形式  
        return String.valueOf(randString.charAt(index));  
    }  
    /**
     * 獲取隨機指定區(qū)間的隨機數(shù) 
     * @param min (指定最小數(shù)) 
     * @param max (指定最大數(shù)) 
     * @return 
     */
    private static int getRandomNum(int min,int max) { 
    	return RandomUtils.nextInt(min, max);
    }  
    /** 
     * 獲得字體 
     * @return 
     */  
    private static Font getFont() {  
        return new Font("Fixedsys", Font.CENTER_BASELINE, 25);  //名稱、樣式、磅值  
    }  
    /** 
     * 獲得顏色 
     * @param fc 
     * @param bc 
     * @return 
     */  
    private static Color getRandColor(int frontColor, int backColor) {  
        if(frontColor > 255)  
            frontColor = 255;  
        if(backColor > 255)  
            backColor = 255;  
        int red = frontColor + random.nextInt(backColor - frontColor - 16);  
        int green = frontColor + random.nextInt(backColor - frontColor -14);  
        int blue = frontColor + random.nextInt(backColor - frontColor -18);  
        return new Color(red, green, blue);  
    }  
    /** 
     * 繪制字符串,返回繪制的字符串 
     * @param g 
     * @param randomString 
     * @param i 
     * @return 
     */  
    private static String drawString(Graphics g, String randomString, int i) { 
    	Graphics2D g2d = (Graphics2D) g;
    	g2d.setFont(getFont());   //設置字體  
    	g2d.setColor(new Color(random.nextFloat(), random.nextFloat(), random.nextFloat()));//設置顏色  
        String randChar = String.valueOf(getRandomChar(random.nextInt(randString.length())));  
        randomString += randChar;   //組裝  
        int rot = getRandomNum(5,10);
        g2d.translate(random.nextInt(3), random.nextInt(3)); 
        g2d.rotate(rot * Math.PI / 180);
        g2d.drawString(randChar, 13*i, 20);   
        g2d.rotate(-rot * Math.PI / 180);
        return randomString;  
    }  
    /** 
     * 繪制干擾線 
     * @param g 
     */  
    private static void drawLine(Graphics g) {  
        //起點(x,y)  偏移量x1、y1  
        int x = random.nextInt(width);  
        int y = random.nextInt(height);  
        int xl = random.nextInt(13);  
        int yl = random.nextInt(15);  
        g.setColor(new Color(random.nextFloat(), random.nextFloat(), random.nextFloat()));
        g.drawLine(x, y, x + xl, y + yl);  
    }  
    /**
     * 
     * @MethodName: getRandomCode
     * @Description: 生成Base64圖片驗證碼
     * @param key
     * @return String 返回base64
     */
    public static Validate getRandomCode() {  
    	validate = validate==null?new Validate():validate;
        // BufferedImage類是具有緩沖區(qū)的Image類,Image類是用于描述圖像信息的類  
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_BGR);  
        Graphics g = image.getGraphics();// 獲得BufferedImage對象的Graphics對象  
        g.fillRect(0, 0, width, height);//填充矩形  
        g.setFont(new Font("Times New Roman", Font.ROMAN_BASELINE, 18));//設置字體  
        g.setColor(getRandColor(110, 133));//設置顏色  
        //繪制干擾線  
        for(int i = 0; i <= lineSize; i++) {  
            drawLine(g);  
        }  
        //繪制字符  
        String randomString = "";  
        for(int i = 1; i <= StringNum; i++) {  
            randomString = drawString(g, randomString, i); 
            validate.setValue(randomString);
        }  
        g.dispose();//釋放繪圖資源  
        ByteArrayOutputStream bs = null;
        try {  
            bs = new ByteArrayOutputStream();
            ImageIO.write(image, "png", bs);//將繪制得圖片輸出到流  
            String imgsrc = Base64.byteArrayToBase64(bs.toByteArray());
            validate.setBase64Str(imgsrc);
        } catch (Exception e) {  
            e.printStackTrace();  
        } finally {  
        	try {
				bs.close();
			} catch (IOException e) {
				e.printStackTrace();
			}finally{
				bs = null;
			}
        }     
        return validate;
    }  
    /**
     * 
     * @ClassName: Validate
     * @Description: 驗證碼類
     * @author chenhx
     * @date 2017年11月14日 上午11:35:34
     */
    public static class Validate implements Serializable{
    	private static final long serialVersionUID = 1L;
    	private String Base64Str;		//Base64 值
    	private String value;			//驗證碼值
    	public String getBase64Str() {
    		return Base64Str;
    	}
    	public void setBase64Str(String base64Str) {
    		Base64Str = base64Str;
    	}
    	public String getValue() {
    		return value;
    	}
    	public void setValue(String value) {
    		this.value = value;
    	}
    }
}  
 

Validate v = ValidateCodeUtil.getRandomCode();     //直接調(diào)用靜態(tài)方法，返回驗證碼對象
if(v!=null){
	session.setAttribute("validate", MD5Util.md5(v.getValue().toLowerCase()));	//將驗證碼值保存session
	result.setResult(v.getBase64Str());
	result.setResultCode(0);
	result.setMsg("刷新驗證碼成功");
}

 <img id="validateImg" src="data:image/png;base64,${validate }" alt="點擊刷新" />