EntityManager returns NullPointerException when persisting

问题

When I persist a "Joueur" (cf my class below), I get a NullPointerException, but I don't know why

em.persist(new Joueur("pseudo", "mdp", "mail"));

This is my class "Joueur" :

@Entity
@NamedQueries({
@NamedQuery(name = "trouverParMail", query = "SELECT * FROM Joueur j WHERE j.mail = :mail")})
public class Joueur implements Serializable {
private static final long serialVersionUID = 1L;

private String pseudo;
private String mdp;
private String mail;
private Integer nbParties;
private Integer nbPartiesGagnees;

public Joueur() {
}

public Joueur(String pseudo, String mdp, String mail)
{
    this.pseudo = pseudo;
    this.mdp = mdp;
    this.mail = mail;

    this.nbParties = 0;
    this.nbPartiesGagnees = 0;
}

@Id
public String getPseudo()
{
    return pseudo;
}

public String getMdp()
{
    return mdp;
}

public String getMail()
{
    return mail;
}

public Integer getNbParties()
{
    return nbParties;
}

public Integer getNbPartieGagnees()
{
    return nbPartiesGagnees;
}

public void setPseudo(String pseudo) {
    this.pseudo = pseudo;
}

public void setMdp(String mdp) {
    this.mdp = mdp;
}

public void setMail(String mail) {
    this.mail = mail;
}

public void setNbParties(Integer nbParties)
{
    this.nbParties = nbParties;
}

public void setNbPartiesGagnees(Integer nbPartiesGagnees)
{
    this.nbPartiesGagnees = nbPartiesGagnees;
}

}

and the error stack :

java.lang.NullPointerException
at login.LoginBean.inscription(LoginBean.java:46)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.glassfish.ejb.security.application.EJBSecurityManager.runMethod(EJBSecurityManager.java:1052)
at org.glassfish.ejb.security.application.EJBSecurityManager.invoke(EJBSecurityManager.java:1124)
at com.sun.ejb.containers.BaseContainer.invokeBeanMethod(BaseContainer.java:5388)
at com.sun.ejb.EjbInvocation.invokeBeanMethod(EjbInvocation.java:619)
at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:800)
at com.sun.ejb.EjbInvocation.proceed(EjbInvocation.java:571)
at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.doAround(SystemInterceptorProxy.java:162)
at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.aroundInvoke(SystemInterceptorProxy.java:144)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.sun.ejb.containers.interceptors.AroundInvokeInterceptor.intercept(InterceptorManager.java:861)
at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:800)
at com.sun.ejb.containers.interceptors.InterceptorManager.intercept(InterceptorManager.java:370)
at com.sun.ejb.containers.BaseContainer.__intercept(BaseContainer.java:5360)
at com.sun.ejb.containers.BaseContainer.intercept(BaseContainer.java:5348)
at com.sun.ejb.containers.EJBObjectInvocationHandler.invoke(EJBObjectInvocationHandler.java:206)
at com.sun.ejb.containers.EJBObjectInvocationHandlerDelegate.invoke(EJBObjectInvocationHandlerDelegate.java:79)
at $Proxy255.inscription(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.sun.corba.ee.impl.presentation.rmi.StubInvocationHandlerImpl.privateInvoke(StubInvocationHandlerImpl.java:241)
at com.sun.corba.ee.impl.presentation.rmi.StubInvocationHandlerImpl.invoke(StubInvocationHandlerImpl.java:152)
at com.sun.corba.ee.impl.presentation.rmi.codegen.CodegenStubBase.invoke(CodegenStubBase.java:227)
at login.__LoginRemote_Remote_DynamicStub.inscription(login/__LoginRemote_Remote_DynamicStub.java)
at login._LoginRemote_Wrapper.inscription(login/_LoginRemote_Wrapper.java)
at org.apache.jsp.inscription_jsp._jspService(inscription_jsp.java from :95)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:111)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:770)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:403)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:473)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:377)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:770)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1542)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:281)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:655)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:595)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:161)
at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:331)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:231)
at com.sun.enterprise.v3.services.impl.ContainerMapper$AdapterCallable.call(ContainerMapper.java:317)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:195)
at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:849)
at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:746)
at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1045)
at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:228)
at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)
at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)
at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)
at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)
at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)
at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)
at com.sun.grizzly.ContextTask.run(ContextTask.java:71)
at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)
at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)
at java.lang.Thread.run(Thread.java:680)

Do you know where is the error ? Tkx

回答1:

According description you gave, origin of NullPointerException is in this line:

em.persist(new Joueur("pseudo", "mdp", "mail"));

Only possible cause is that em is null. Likely reason for it being null is that LoginBean failed to inject EntityManager. If so, maybe LoginBean is not container managed component? Maybe you forgot @Stateless annotation?

If this didn't answered to your question, you have to share more details: