使用servlet时，我遇到一个问题，我试图在验证码servlet中绘制一个验证码，然后使用自定义标签显示它。但是我有一个问题，我的验证码标记正在向后退，它没有获取我的验证码的实际ID，因此我无法检查输入的参数进行验证，因为ID不匹配。我当时正在考虑为注册servlet生成一个验证码，将其放入会话中，然后将其转移到验证码servlet并在那里绘制。以这种方式byte [] gg = req.getSession().getAtribute("captchaId);，但是在那种情况下，我得到了ClassCastException。如何正确显示ID并将其放入标签？
Registration servlet:
protected void doGet(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) throws ServletException, IOException {
startTime = System.currentTimeMillis();
// CaptchaGenerator captchaGenerator = new CaptchaGenerator(captchaService);
// ByteArrayOutputStream baos = new ByteArrayOutputStream();
// captchaGenerator.generateCaptcha(httpServletResponse, baos);
// httpServletRequest.getSession().setAttribute(captchaService.getId(), baos.t
oByteArray());
// httpServletRequest.getSession().setAttribute("captchaId", captchaService.getId());
httpServletRequest.getRequestDispatcher(ConstantApp.JSPPages.REGISTRATION_PAGE).forward(httpServletRequest, httpServletResponse);
}
CaptchaTag：
public class CaptchaCustomTag extends SimpleTagSupport {
private static final Logger LOG = Logger.getLogger(CaptchaCustomTag.class);
private String captchaId;
public void setCaptchaId(String captchaId) {
this.captchaId = captchaId;
}
private String getCaptchaPNG() {
return "<img src=\"captcha?id=" + captchaId + "\">";
}
private String getHidden() {
return "<input type=\"hidden\" name=\"captchaID\" value=\"" + captchaId + "\">\n";
}
@Override
public void doTag() throws JspException, IOException {
getJspContext().getOut().write(getCaptchaPNG() + getHidden());
LOG.debug("Captcha id: " + captchaId);
}
}
CaptchaServlet：
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
CaptchaTypeManager captchaTypeManager = new CaptchaTypeManager(req, resp, captchaService);
CaptchaGenerator captchaGenerator = new CaptchaGenerator(captchaService);
captchaTypeManager.getType(getServletContext().getInitParameter(ConstantApp.ContextType.CONTEXT_TYPE));
byte[] captcha = (byte[]) req.getSession().getAttribute(req.getParameter("captchaId"));
if (captcha == null) {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
captchaGenerator.generateCaptcha(resp, baos);
captcha = baos.toByteArray();
req.getSession().setAttribute(captchaService.getId(), baos.toByteArray());
req.getSession().setAttribute("captchaId", captchaService.getId());
}
IOUtils.copy(new ByteArrayInputStream(captcha), resp.getOutputStream());
LOG.debug(getServletContext().getInitParameter(ConstantApp.ContextType.CONTEXT_TYPE));
}
验证码标签tld：
<taglib xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
version="2.0">
<tlib-version>2.1</tlib-version>
<short-name>MyTags</short-name>
<uri>http://journaldev.com/jsp/tlds/MyTags</uri>
<tag>
<name>captcha</name>
<tag-class>com.epam.preproduction.linnyk.customtag.CaptchaCustomTag</tag-class>
<body-content>empty</body-content>
<attribute>
<name>captchaId</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
</taglib>
registration.jsp：
<form action="registration" method="post" id="registration_form">
<ul>
<h2><div align="center" style="color: #ff0000">${requestScope.error_time}</div></h2>
<ul>
<div id="error_first_name" style="color: #ff0000">${requestScope.error_first_name}</div>
<li class="text-info">First Name:</li>
<li><input type="text" id="fName" name="fName" placeholder="Your first name" value="${sessionScope.fName}"></li>
</ul>
<ul>
<div id="error_last_name" style="color: #ff0000">${requestScope.error_last_name}</div>
<li class="text-info">Last Name:</li>
<li><input type="text" id="lName" name="lName" placeholder="Your last name" value="${sessionScope.lName}"></li>
</ul>
<ul>
<div id="error_login" style="color: #ff0000">${requestScope.error_login}</div>
<li class="text-info">Login:</li>
<li><input type="text" id="login" name="login" placeholder="Your login" value="${sessionScope.login}"></li>
</ul>
<ul>
<div id="error_email" style="color: #ff0000">${requestScope.error_email}</div>
<li class="text-info">Email:</li>
<li><input type="text" id="email" name="email" placeholder="Your email" value="${sessionScope.email}"></li>
</ul>
<ul>
<div id="error_password" style="color: #ff0000">${requestScope.error_password}</div>
<li class="text-info">Password:</li>
<li><input type="password" id="pass" name="pass" placeholder="Your password"></li>
</ul>
<ul>
<div id="error_confirmPassword" style="color: #ff0000">${requestScope.error_confirmPassword}</div>
<li class="text-info">Re-enter Password:</li>
<li><input type="password" id="confPass" name="confPass" placeholder="Confirm your password"></li>
</ul>
<MyTags:captcha captchaId = "${captchaId}"/>
<br></br>
<div style="color: #ff0000" id="error_captcha">${requestScope.error_captcha}</div>
<input type="text" placeholder="Enter the code from the image" name="captchaCode" id="captchaCode"/>
<input type="submit" id="submit" value="Register Now">
<p class="click">By clicking this button, you agree to my modern style <a href="terms.jsp">Policy Terms and
Conditions</a> to Use</p>
</form>
由于我的代码的加载时间早于验证码Servlet的加载时间，因此ID会在稍后的步骤到达那里。如何正确实施？
如果我取消了代码在regestant servlet中的注释，然后在验证码servlet中注释了代码，那么我得到了一个种姓类，该如何实现呢？
byte[] captcha = (byte[]) req.getSession().getAttribute("captchaId");