在GWT-Ext 2.0.3中實現驗證碼

Question

大家好，
我正在使用GWT-Ext 2.0.3。我在我的項目中實現了SimpleCaptcha。當我重新加載面板時，我無法刷新驗證碼圖像。我正在使用simplecaptcha-1.2.1.jar文件來實現驗證碼。

我創建了一個servlet來顯示驗證碼圖像。

import java.io.IOException; 

import javax.servlet.ServletException; 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 
import javax.servlet.http.HttpSession; 

import nl.captcha.Captcha; 
import nl.captcha.backgrounds.GradiatedBackgroundProducer; 
import nl.captcha.servlet.CaptchaServletUtil; 
import nl.captcha.servlet.SimpleCaptchaServlet; 

public class ExtendedCaptchaServlet extends SimpleCaptchaServlet { 

    private static final long serialVersionUID = -3280477565969758716L; 

    //@Override 
    public void doGet(HttpServletRequest req, HttpServletResponse resp) 

    throws ServletException, IOException { 

     HttpSession session = req.getSession(); 

     Captcha captcha = new Captcha.Builder(200, 50) 

     .addText() 

     .addBackground(new GradiatedBackgroundProducer()).addNoise() 

     .addBorder() 

     .build(); 

     session.setAttribute("captcha", captcha); 
     CaptchaServletUtil.writeImage(resp, captcha.getImage()); 

    } 
} 

在web.xml中輸入

<servlet> 
    <servlet-name>SimpleCaptcha</servlet-name> 
    <servlet-class> com.server.test.ExtendedCaptchaServlet 
    </servlet-class> 
</servlet> 
<servlet-mapping> 
    <servlet-name>SimpleCaptcha</servlet-name> 
    <url-pattern>/SimpleCaptcha.jpg</url-pattern> 
</servlet-mapping> 

我的GWT面板

FormPanel formPanel = new FormPanel(); 
Image captchaImage = new Image("/SimpleCaptcha.jpg"); 
formPanel.add(captchaImage); 

這是顯示新的驗證碼圖像，每次當我刷新瀏覽器從頁面。但是，當我重新加載表單面板時，它不顯示圖像。

誰能幫助我？

Answer 1

嘗試添加「時間戳」

Image captchaImage = new Image("/SimpleCaptcha.jpg?" + Math.floor(Math.random()*100));