Retrieving class from hibernate throws nullpointerexception

Question

I'm having java.lang.NullPointerException when I'm retrieving a class from my database through hibernate.

protected void login(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

    String username = request.getParameter("username");
    String password = request.getParameter("password");

    SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();
    Session session1 = sessionFactory.openSession();
    session1.beginTransaction();

    User user = (User)session1.get(User.class, username); 

    System.out.println(user.getUsername());
    System.out.println(user.getPassword());

    if (user.getPassword().equals(password)) {

        request.setAttribute("user", user);

        request.setAttribute("loggedIn", "true");

        session1.getTransaction().commit();
        session1.close();
        sessionFactory.close();

        request.getRequestDispatcher("/WEB-INF/jsp/view/mainPage.jsp").forward(request, response);

    } else {

        session1.getTransaction().commit();
        session1.close();
        sessionFactory.close();

        request.setAttribute("loggedIn", "false");

        request.getRequestDispatcher("/WEB-INF/jsp/view/startPage.jsp").forward(request, response);
    }
}

This is my method in my servlet which handles login. (Not sure if I'm using the sessionFactory optimal). From my two lines after the session.get(Class, arg)

System.out.println(user.getUsername());
System.out.println(user.getPassword());

I get the correct values, so I surpose that I successfully retrieve the object, also when I add // to

//request.setAttribute("user", user);

It works fine. The excpetion was also thrown when I make the requestDispatcher.

I'm assuming it has something to do with the ArrayList which my user has. Here's the user.

@Entity
public class User {

@GeneratedValue(strategy=GenerationType.AUTO) 
private long empId;
@Id
private String username;
private String firstname;
private String lastname;
private String organisation;
private String password;
private String email;

@OneToMany
private Collection<Marker> bookmarks = new ArrayList<>();

public User() {

}

public User(String username, String password, String email) {
    this.username = username;
    this.password = password;
    this.email = email;
}

public Collection<Marker> getBookmarks() {
    return bookmarks;
}

public void setBookmarks(Collection<Marker> bookmarks) {
    this.bookmarks = bookmarks;
}

public String getUsername() {
    return username;
}

public void setUsername(String username) {
    this.username = username;
}

public String getPassword() {
    return password;
}

public void setPassword(String password) {
    this.username = password;
}

public String getEmail() {
    return email;
}

public void setEmail(String email) {
    this.username = email;
}

public long getEmpId() {
    return empId;
}

public void setEmpId(long empId) {
    this.empId = empId;
}

public String getFirstname() {
    return firstname;
}

public void setFirstname(String firstname) {
    this.firstname = firstname;
}

public String getLastname() {
    return lastname;
}

public void setLastname(String lastname) {
    this.lastname = lastname;
}

public String getOrganisation() {
    return organisation;
}

public void setOrganisation(String organisation) {
    this.organisation = organisation;
}

@Override
public String toString()
{
    return this.username;
}

}

Here's the console log:

java.lang.NullPointerException
    at org.hibernate.collection.internal.AbstractPersistentCollection.openTemporarySessionForLoading(AbstractPersistentCollection.java:273)
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:200)
    at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:541)
    at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:132)
    at org.hibernate.collection.internal.PersistentBag.iterator(PersistentBag.java:277)
    at org.apache.taglibs.standard.tag.common.core.ForEachSupport.toForEachIterator(ForEachSupport.java:348)
    at org.apache.taglibs.standard.tag.common.core.ForEachSupport.supportedTypeForEachIterator(ForEachSupport.java:224)
    at org.apache.taglibs.standard.tag.common.core.ForEachSupport.prepare(ForEachSupport.java:155)
    at javax.servlet.jsp.jstl.core.LoopTagSupport.doStartTag(LoopTagSupport.java:256)
    at org.apache.jsp.WEB_002dINF.jsp.view.mainPage_jsp._jspx_meth_c_005fforEach_005f0(mainPage_jsp.java:354)
    at org.apache.jsp.WEB_002dINF.jsp.view.mainPage_jsp._jspService(mainPage_jsp.java:313)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:431)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:721)
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:466)
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:391)
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:318)
    at com.Tooblo.eventHandler.login(eventHandler.java:195)
    at com.Tooblo.eventHandler.doGet(eventHandler.java:61)
    at com.Tooblo.eventHandler.doPost(eventHandler.java:212)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668)
    at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:223)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1517)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1474)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Unknown Source)

sep. 24, 2015 6:08:04 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [eventHandler] in context with path [/Toobloo] threw exception [java.lang.NullPointerException] with root cause
java.lang.NullPointerException
    at org.hibernate.collection.internal.AbstractPersistentCollection.openTemporarySessionForLoading(AbstractPersistentCollection.java:273)
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:200)
    at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:541)
    at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:132)
    at org.hibernate.collection.internal.PersistentBag.iterator(PersistentBag.java:277)
    at org.apache.taglibs.standard.tag.common.core.ForEachSupport.toForEachIterator(ForEachSupport.java:348)
    at org.apache.taglibs.standard.tag.common.core.ForEachSupport.supportedTypeForEachIterator(ForEachSupport.java:224)
    at org.apache.taglibs.standard.tag.common.core.ForEachSupport.prepare(ForEachSupport.java:155)
    at javax.servlet.jsp.jstl.core.LoopTagSupport.doStartTag(LoopTagSupport.java:256)
    at org.apache.jsp.WEB_002dINF.jsp.view.mainPage_jsp._jspx_meth_c_005fforEach_005f0(mainPage_jsp.java:354)
    at org.apache.jsp.WEB_002dINF.jsp.view.mainPage_jsp._jspService(mainPage_jsp.java:313)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:431)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:721)
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:466)
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:391)
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:318)
    at com.Tooblo.eventHandler.login(eventHandler.java:195)
    at com.Tooblo.eventHandler.doGet(eventHandler.java:61)
    at com.Tooblo.eventHandler.doPost(eventHandler.java:212)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:668)
    at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:223)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1517)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1474)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Unknown Source)

What's wierd is that it seem to work before I changed database connection, the new one is on my other computer.

Can you add System.out.println(session1) to check whether session1 object is not null ? Also for read operations, we don't need transaction, so you should remove session1.beginTransaction() and session1.getTransaction().commit() statements. — Vasu, Commented Sep 24, 2015 at 16:17
system.out.println(session1) return a very long string with some PersistenceContext. Removed the getTransactions :) — JonCode, Commented Sep 24, 2015 at 16:24
can you provide the data present in the USER table ? Also tell me what you are entering ? Any spaces, case sensitives ? Seems like you DON'T HAVE RECORDS in database WHAT YOU ARE LOOKING FOR. — Vasu, Commented Sep 24, 2015 at 16:31
@OneToMany(fetch=FetchType.EAGER) Worked! Can you make an answer and I'll mark it as correct. Also could you explain what that annotation does? — JonCode, Commented Sep 24, 2015 at 16:36

Community · Accepted Answer · 2017-05-23 12:29:37Z

2

Try @OneToMany(fetch=FetchType.EAGER). It basically loads the relationships whenever the main entity is loaded. It may not be a good approach always. This links: Difference between FetchType LAZY and EAGER in Java Persistence API? & when to use Lazy loading / Eager loading in hibernate? will give you a better idea.

edited May 23, 2017 at 12:29

CommunityBot

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answered Sep 24, 2015 at 16:42

user2953113

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yogidilip · Accepted Answer · 2015-09-24 16:21:48Z

1

Couple of things.

You need to separate your DB logic from your servlet class. Create a new service/DAO layer and call your service from your servlet.
You need to be careful while creating sessionFactory. Each time you create a new sessionFactory, you will open a new connection to DB. You don't want that. Implement a singleton pattern for sessionFactory and share it.
Make sure you open and close your session properly after making each hibernate call.

answered Sep 24, 2015 at 16:21

yogidilip

7907 silver badges23 bronze badges

I was sudden this was not the best practise. But thought I would try to make it work, and optimize my code for efficiency later. But thanks for giving some pointers!
– JonCode
Commented Sep 24, 2015 at 16:26

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