java實現驗證碼

/*******************************sping mvc controller***********************************/

//獲取驗證碼
    @Path("identifying")
    @GET
    public void getIdentifying(@Context HttpServletRequest request,@Context HttpServletResponse response){
            response.setContentType("image/jpeg");//設定相應型別,告訴瀏覽器輸出的內容為圖片
            response.setHeader("Pragma", "No-cache");//設定響應頭資訊，告訴瀏覽器不要快取此內容
            response.setHeader("Cache-Control", "no-cache");
            response.setDateHeader("Expire", 0);
            RandomValidateCode randomValidateCode = new RandomValidateCode();
            try {
                randomValidateCode.getRandcode(request, response);//輸出圖片方法
            } catch (Exception e) {
                e.printStackTrace();
            }
    }

/*******************************util返回動態驗證碼圖片***********************************/

package com.netutel.web.util;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class RandomValidateCode {
    public static final String RANDOMCODEKEY = "rand";// 放到session中的key
    private Random random = new Random();
    private String randString = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";// 隨機產生的字串

    private int width = 80;// 圖片寬
    private int height = 26;// 圖片高
    private int lineSize = 40;// 干擾線數量
    private int stringNum = 4;// 隨機產生字元數量

    /*
     * 獲得字型
     */
    private Font getFont() {
        return new Font("Fixedsys", Font.CENTER_BASELINE, 18);
    }

    /*
     * 獲得顏色
     */
    private Color getRandColor(int fc, int bc) {
        if (fc > 255)
            fc = 255;
        if (bc > 255)
            bc = 255;
        int r = fc + random.nextInt(bc - fc - 16);
        int g = fc + random.nextInt(bc - fc - 14);
        int b = fc + random.nextInt(bc - fc - 18);
        return new Color(r, g, b);
    }

    /**
     * 生成隨機圖片
     */
    public void getRandcode(HttpServletRequest request,
            HttpServletResponse response) {
        HttpSession session = request.getSession();
        // BufferedImage類是具有緩衝區的Image類,Image類是用於描述影像資訊的類
        BufferedImage image = new BufferedImage(width, height,
                BufferedImage.TYPE_INT_BGR);
        Graphics g = image.getGraphics();// 產生Image物件的Graphics物件,改物件可以在影像上進行各種繪製操作
        g.fillRect(0, 0, width, height);
        g.setFont(new Font("Times New Roman", Font.ROMAN_BASELINE, 18));
        g.setColor(getRandColor(110, 133));
        // 繪製干擾線
        for (int i = 0; i <= lineSize; i++) {
            drowLine(g);
        }
        // 繪製隨機字元
        String randomString = "";
        for (int i = 1; i <= stringNum; i++) {
            randomString = drowString(g, randomString, i);
        }
        session.removeAttribute(RANDOMCODEKEY);
        session.setAttribute(RANDOMCODEKEY, randomString);
        g.dispose();
        try {
            ImageIO.write(image, "JPEG", response.getOutputStream());// 將記憶體中的圖片通過流動形式輸出到客戶端
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /*
     * 繪製字串
     */
    private String drowString(Graphics g, String randomString, int i) {
        g.setFont(getFont());
        g.setColor(new Color(random.nextInt(101), random.nextInt(111), random
                .nextInt(121)));
        String rand = String.valueOf(getRandomString(random.nextInt(randString
                .length())));
        randomString += rand;
        g.translate(random.nextInt(3), random.nextInt(3));
        g.drawString(rand, 13 * i, 16);
        return randomString;
    }

    /*
     * 繪製干擾線
     */
    private void drowLine(Graphics g) {
        int x = random.nextInt(width);
        int y = random.nextInt(height);
        int xl = random.nextInt(13);
        int yl = random.nextInt(15);
        g.drawLine(x, y, x + xl, y + yl);
    }

    /*
     * 獲取隨機的字元
     */
    public String getRandomString(int num) {
        return String.valueOf(randString.charAt(num));
    }
}
/*******************************jsp發起呼叫***********************************/

<li><img title="點選更換" onclick="javascript:refresh(this);" src="ws/user/identifying"></li>

/*******************************js***********************************/

function refresh(obj) {
    obj.src = "ws/user/identifying?"+Math.random();
}