在GWT-Ext 2.0.3中实现Captcha

Question

大家好，

我使用的是GWT-Ext 2.0.3。我在我的项目中实现了SimpleCaptcha，当我重新加载该面板时，无法刷新captcha映像，我正在使用simplecaptcha-1.2.1.jar文件来执行captcha。

​

• I创建了一个servlet来显示captcha图像.

​

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());

    }
}

​

• Entry in web.xml

​

<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>

​

• My GWT Panel

​

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

每当我从浏览器刷新页面时，它都会显示新的captcha图像。但当我重新加载表单面板时，它不会显示图像。

有谁可以帮我？

Answer 1

尝试添加“时间戳”

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