HTTP状态500 - 实例化servlet类com.marlabs.demo.XMLServlet时出错

Question

我正在开发一个简单的webapp，我在注册用户时遇到以下错误。 HTTP状态500 - 实例化servlet类com.marlabs.demo.XMLServlet

时出错

web.xml如下

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://xmlns.jcp.org/xml/ns/javaee"
    xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
    id="WebApp_ID" version="3.1">
    <display-name>SimpleServletProject</display-name>
    <welcome-file-list>
        <welcome-file>index.html</welcome-file>
    </welcome-file-list>

    <servlet>
        <servlet-name>XMLServlet</servlet-name>
        <servlet-class>com.marlabs.demo.XMLServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>XMLServlet</servlet-name>
        <url-pattern>/XMLServlet</url-pattern>
    </servlet-mapping>

</web-app>

我的servlet如下

package com.marlabs.demo;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

@SuppressWarnings("serial")
@WebServlet(description = "A simple servlet", urlPatterns = { "/XMLServlet" })
public class XMLServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html");
        PrintWriter pout = response.getWriter();
        String emailID = request.getParameter("emailID");
        String pass = request.getParameter("pass");
        String fname = request.getParameter("fname");
        String lname = request.getParameter("lname");

        HttpSession sess = request.getSession();
        ServletContext context = request.getServletContext();
        if (emailID != "" && emailID != null) {
            sess.setAttribute("savedEmail", emailID);
            context.setAttribute("savedEmail", emailID);
        }

        pout.println("Hello " + fname + "<br/>");

        UserDetails user = new UserDetails();
        user.setEmailID(emailID);
        user.setPass(pass);
        user.setFname(fname);
        user.setLname(lname);

        @SuppressWarnings("deprecation")
        SessionFactory sessionFactory = new Configuration().configure("hibernate.cfg.xml").buildSessionFactory();
        Session session = sessionFactory.openSession();
        session.beginTransaction();
        session.save(user);
        session.getTransaction().commit();
        session.close();

        pout.println("Your information is saved!");
    }
}