html 註冊驗證碼

java代碼：

public class CaptchaRender implements Serializable{

private static final long serialVersionUID = -916701543933591834L;
private static final int WIDTH = 62, HEIGHT = 20;
private static final String[] strArr = {"3", "4", "5", "6", "7", "8", "9", "A", "B", "C", "D", "E", "F", "G", "H", "J", "K", "M", "N", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y"};

private String randomCodeKey;

public CaptchaRender(String randomCodeKey) {
if (StringKit.isBlank(randomCodeKey))
throw new IllegalArgumentException("randomCodeKey can not be blank");
this.randomCodeKey = randomCodeKey;
}

public void render() {
BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
String vCode = drawGraphic(image);
vCode = encrypt(vCode);
Cookie cookie = new Cookie(randomCodeKey, vCode);
cookie.setMaxAge(-1);
cookie.setPath("/");
response.addCookie(cookie);
response.setHeader("Pragma","no-cache");
        response.setHeader("Cache-Control","no-cache");
        response.setDateHeader("Expires", 0);
        response.setContentType("image/jpeg");
        
        ServletOutputStream sos = null;
        try {
sos = response.getOutputStream();
ImageIO.write(image, "jpeg",sos);
} catch (Exception e) {
throw new RuntimeException(e);
}
finally {
if (sos != null)
try {sos.close();} catch (IOException e) {e.printStackTrace();}
}
}

private String drawGraphic(BufferedImage image){
// 擷取圖形上下文
Graphics g = image.createGraphics();
// 產生隨機類
Random random = new Random();
// 設定背景色
g.setColor(getRandColor(200, 250));
g.fillRect(0, 0, WIDTH, HEIGHT);
// 設定字型
g.setFont(new Font("Times New Roman", Font.PLAIN, 18));

// 隨機產生155條幹擾線，使圖象中的認證碼不易被其它程式探測到
g.setColor(getRandColor(160, 200));
for (int i = 0; i < 155; i++) {
int x = random.nextInt(WIDTH);
int y = random.nextInt(HEIGHT);
int xl = random.nextInt(12);
int yl = random.nextInt(12);
g.drawLine(x, y, x + xl, y + yl);
}

// 取隨機產生的認證碼(4位元字)
String sRand = "";
for (int i = 0; i < 4; i++) {
String rand = String.valueOf(strArr[random.nextInt(strArr.length)]);
sRand += rand;
// 將認證碼顯示到圖象中
g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));
// 調用函數出來的顏色相同，可能是因為種子太接近，所以只能直接產生
g.drawString(rand, 13 * i + 6, 16);
}

// 圖象生效
g.dispose();
return sRand;
}

/*
* 給定範圍獲得隨機顏色
*/
private Color getRandColor(int fc, int bc) {
Random random = new Random();
if (fc > 255)
fc = 255;
if (bc > 255)
bc = 255;
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);
}

private static final String encrypt(String srcStr) {
try {
String result = "";
MessageDigest md = MessageDigest.getInstance("MD5");
byte[] bytes = md.digest(srcStr.getBytes("utf-8"));
for(byte b:bytes){
String hex = Integer.toHexString(b&0xFF).toUpperCase();
result += ((hex.length() ==1 ) ? "0" : "") + hex;
}
return result;
} catch (Exception e) {
throw new RuntimeException(e);
}
}

}

html代碼：

<input type="text" maxlength="6" id="random_code" name="random_code" style="width:80px;">
<img alt="" id="image" name="image" src="img" onclick="changeImg();" style="cursor: pointer; position: relative;" border="0" />
<a href="#" onclick="changeImg();"><span class="login_style">看不清？</span></a>

js調用：

function changeImg()
{
$("#image").attr("src",'/img?s='+Math.random());
}

備忘：

在teomcat中有一個臨時檔案夾temp，頁面出現的驗證碼一直是X，後來查資料室因為temp臨時檔案刪掉，找不到這個