SEVERE: java.lang.IllegalArgumentException: attempt to create saveOrUpdate event with null entity
        at org.hibernate.event.SaveOrUpdateEvent.<init>(SaveOrUpdateEvent.java:40)
        at org.hibernate.event.SaveOrUpdateEvent.<init>(SaveOrUpdateEvent.java:23)
        at org.hibernate.impl.SessionImpl.save(SessionImpl.java:523)
        at org.hibernate.impl.SessionImpl.save(SessionImpl.java:519)
        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.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:301)
        at com.sun.proxy.$Proxy107.save(Unknown Source)
        at bean.imageUpload.save(imageUpload.java:48)
        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.el.parser.AstValue.invoke(AstValue.java:234)
        at com.sun.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:297)
        at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:98)
        at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:88)
        at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
        at javax.faces.component.UICommand.broadcast(UICommand.java:315)
        at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:775)
        at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1267)
        at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:82)
        at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
        at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
        at javax.faces.webapp.FacesServlet.service(FacesServlet.java:312)
        at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1523)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:343)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:215)
        at org.primefaces.webapp.filter.FileUploadFilter.doFilter(FileUploadFilter.java:98)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:256)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:215)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:277)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:188)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:641)
        at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:97)
        at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:85)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:185)
        at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:325)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:226)
        at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:165)
        at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:791)
        at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:693)
        at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:954)
        at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:170)
        at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:135)
        at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:102)
        at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:88)
        at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:76)
        at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:53)
        at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:57)
        at com.sun.grizzly.ContextTask.run(ContextTask.java:69)
        at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:330)
        at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:309)
        at java.lang.Thread.run(Thread.java:662)

<h:form enctype="multipart/form-data">
    <p:fileUpload fileUploadListener="#{imageUpload.handleFileUpload}" mode="simple" dragDropSupport="false"
                  update="messages" sizeLimit="100000" fileLimit="3" allowTypes="/(\.|\/)(gif|jpe?g|png)$/" />
    <p:commandButton value="Save" action="#{imageUpload.save}" />
    <p:growl id="messages" showDetail="true"/>
</h:form>

public class imageUpload implements Serializable {

    private Products seletedproduct;
    private List<Products> product;
    private byte[] img;

    /** Creates a new instance of imageUpload */
    public imageUpload() {
    }

    public Products getSeletedproduct() {
        return seletedproduct;
    }

    public void setSeletedproduct(Products seletedproduct) {
        this.seletedproduct = seletedproduct;
    }

    public void handleFileUpload(FileUploadEvent event) throws IOException {

        UploadedFile file = event.getFile();
//    byte[] img = org.apache.commons.io.IOUtils.toByteArray(file.getInputstream());
        seletedproduct.setImage(file.getContents());
    }

    public void save(){
        try {
            Session session = HibernateUtil.getSessionFactory().getCurrentSession();
            session.beginTransaction().begin();
            session.save(seletedproduct);
            session.getTransaction().commit();
            session.close();
            System.out.println("Saved Successfully");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

<filter>
    <filter-name>PrimeFaces FileUpload Filter</filter-name>
    <filter-class>org.primefaces.webapp.filter.FileUploadFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>PrimeFaces FileUpload Filter</filter-name>
    <servlet-name>Faces Servlet</servlet-name>
</filter-mapping>