nullPointerException on entity manager methods

[Martin Frisone]

Hi,
I'm working on a desktop application that reads data from a database using persistence manager Toplink and the netbeans IDE.
I have set:

The persistence unit (persistence.xml)

@PersistenceContext annotation

"EntityManager em" class

the entity clases from the DB

the problem comes when I try to execute any of the entity manager methods, such as persist() or find(). It always throws a NullPointerException so I'd like to know where could be my problem. Any idea will help.
Thanks in advance

[Freddy Wong]

Can you provide us with the code and the stacktrace?

[Martin Frisone]

sure....

Persistence Unit "minuto1PU"

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
  <persistence-unit name="minuto1PU" transaction-type="RESOURCE_LOCAL">
    <provider>oracle.toplink.essentials.PersistenceProvider</provider>
    <class>entidades.Clientes</class>
    <class>entidades.Cobros</class>
    <class>entidades.Indicadores</class>
    <class>entidades.Ventas</class>
    <properties>
      <property name="toplink.jdbc.user" value="db2admin"/>
      <property name="toplink.jdbc.password" value="admin"/>
      <property name="toplink.jdbc.url" value="jdbc:db2://localhost:50000/minuto"/>
      <property name="toplink.jdbc.driver" value="com.ibm.db2.jcc.DB2Driver"/>
    </properties>
  </persistence-unit>
</persistence>

Entity class "Cliente"

package entidades;

import java.io.Serializable;
.....
import javax.persistence.Table;

@Entity
@Table(name = "CLIENTES")
public class Clientes implements Serializable {
    private static final long serialVersionUID = 1L;
    
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "IDCLIENTE")//, insertable = false, updatable = false)
    private Integer idcliente;
    
    @Column(name = "DESCRIPCION")
    private String descripcion;
    
    @Basic(optional = false)
    @Column(name = "NOMBRE")    
    private String nombre;

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "idcliente")
    private Collection<Ventas> ventasCollection;

    public Clientes() {
    }

    public Clientes(Integer idcliente) {
        this.idcliente = idcliente;
    }

    public Clientes(String nombre, String descripcion) {
        this.descripcion = descripcion;
        this.nombre = nombre;
    }

    public Integer getIdcliente() {
        return idcliente;
    }

    public void setIdcliente(Integer idcliente) {
        this.idcliente = idcliente;
    }

    public String getDescripcion() {
        return descripcion;
    }

    public void setDescripcion(String descripcion) {
        this.descripcion = descripcion;
    }

    public String getNombre() {
        return nombre;
    }

    public void setNombre(String nombre) {
        this.nombre = nombre;
    }

    public Collection<Ventas> getVentasCollection() {
        return ventasCollection;
    }

    public void setVentasCollection(Collection<Ventas> ventasCollection) {
        this.ventasCollection = ventasCollection;
    }

    @Override
    public int hashCode() {
        int hash = 0;
        hash += (idcliente != null ? idcliente.hashCode() : 0);
        return hash;
    }

    @Override
    public boolean equals(Object object) {
        // TODO: Warning - this method won't work in the case the id fields are not set
        if (!(object instanceof Clientes)) {
            return false;
        }
        Clientes other = (Clientes) object;
        if ((this.idcliente == null && other.idcliente != null) || (this.idcliente != null && !this.idcliente.equals(other.idcliente))) {
            return false;
        }
        return true;
    }

    @Override
    public String toString() {
        return "entidades.Clientes[idcliente=" + idcliente + "]";
    }

}

Main class "Minuto1"

package minuto1;

import entidades.Clientes;
.......
import javax.swing.JFrame;

public class Minuto1View extends FrameView {
    
    @PersistenceContext(unitName="minuto1PU")
    private EntityManager em;    

    public Minuto1View(SingleFrameApplication app) {
        super(app);

        initComponents();

    }

    @Action
    public void showAboutBox() {
        if (aboutBox == null) {
            JFrame mainFrame = Minuto1App.getApplication().getMainFrame();
            aboutBox = new Minuto1AboutBox(mainFrame);
            aboutBox.setLocationRelativeTo(mainFrame);
        }
        Minuto1App.getApplication().show(aboutBox);
    }

    /** This method is called from within the constructor to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        mainPanel = new javax.swing.JPanel();
        jLabel1 = new javax.swing.JLabel();
        jLabel2 = new javax.swing.JLabel();
        jTextField1 = new javax.swing.JTextField();
        jTextField2 = new javax.swing.JTextField();
        jButton1 = new javax.swing.JButton();
        menuBar = new javax.swing.JMenuBar();
        javax.swing.JMenu fileMenu = new javax.swing.JMenu();
        javax.swing.JMenuItem exitMenuItem = new javax.swing.JMenuItem();
        javax.swing.JMenu helpMenu = new javax.swing.JMenu();
        javax.swing.JMenuItem aboutMenuItem = new javax.swing.JMenuItem();
        statusPanel = new javax.swing.JPanel();
        javax.swing.JSeparator statusPanelSeparator = new javax.swing.JSeparator();
        statusMessageLabel = new javax.swing.JLabel();
        statusAnimationLabel = new javax.swing.JLabel();
        progressBar = new javax.swing.JProgressBar();

        mainPanel.setName("mainPanel"); // NOI18N

        org.jdesktop.application.ResourceMap resourceMap = org.jdesktop.application.Application.getInstance(minuto1.Minuto1App.class).getContext().getResourceMap(Minuto1View.class);
        jLabel1.setText(resourceMap.getString("jLabel1.text")); // NOI18N
        jLabel1.setName("jLabel1"); // NOI18N

        jLabel2.setText(resourceMap.getString("jLabel2.text")); // NOI18N
        jLabel2.setName("jLabel2"); // NOI18N

        jTextField1.setText(resourceMap.getString("txtNombre.text")); // NOI18N
        jTextField1.setName("txtNombre"); // NOI18N

        jTextField2.setText(resourceMap.getString("txtDescripcion.text")); // NOI18N
        jTextField2.setName("txtDescripcion"); // NOI18N

        jButton1.setText(resourceMap.getString("btnGuardar.text")); // NOI18N
        jButton1.setName("btnGuardar"); // NOI18N
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton1ActionPerformed(evt);
            }
        });

        javax.swing.GroupLayout mainPanelLayout = new javax.swing.GroupLayout(mainPanel);
        mainPanel.setLayout(mainPanelLayout);
        mainPanelLayout.setHorizontalGroup(
            mainPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(mainPanelLayout.createSequentialGroup()
                .addGap(34, 34, 34)
                .addGroup(mainPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                    .addComponent(jLabel1)
                    .addComponent(jLabel2))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(mainPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                    .addComponent(jTextField2)
                    .addComponent(jTextField1, javax.swing.GroupLayout.DEFAULT_SIZE, 119, Short.MAX_VALUE))
                .addContainerGap(190, Short.MAX_VALUE))
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, mainPanelLayout.createSequentialGroup()
                .addContainerGap(319, Short.MAX_VALUE)
                .addComponent(jButton1)
                .addContainerGap())
        );
        mainPanelLayout.setVerticalGroup(
            mainPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(mainPanelLayout.createSequentialGroup()
                .addGap(24, 24, 24)
                .addGroup(mainPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel1)
                    .addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(mainPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jTextField2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel2))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 150, Short.MAX_VALUE)
                .addComponent(jButton1)
                .addContainerGap())
        );

        menuBar.setName("menuBar"); // NOI18N

        fileMenu.setText(resourceMap.getString("fileMenu.text")); // NOI18N
        fileMenu.setName("fileMenu"); // NOI18N

        javax.swing.ActionMap actionMap = org.jdesktop.application.Application.getInstance(minuto1.Minuto1App.class).getContext().getActionMap(Minuto1View.class, this);
        exitMenuItem.setAction(actionMap.get("quit")); // NOI18N
        exitMenuItem.setName("exitMenuItem"); // NOI18N
        fileMenu.add(exitMenuItem);

        menuBar.add(fileMenu);

        helpMenu.setText(resourceMap.getString("helpMenu.text")); // NOI18N
        helpMenu.setName("helpMenu"); // NOI18N

        aboutMenuItem.setAction(actionMap.get("showAboutBox")); // NOI18N
        aboutMenuItem.setName("aboutMenuItem"); // NOI18N
        helpMenu.add(aboutMenuItem);

        menuBar.add(helpMenu);

        statusPanel.setName("statusPanel"); // NOI18N

        statusPanelSeparator.setName("statusPanelSeparator"); // NOI18N

        statusMessageLabel.setName("statusMessageLabel"); // NOI18N

        statusAnimationLabel.setHorizontalAlignment(javax.swing.SwingConstants.LEFT);
        statusAnimationLabel.setName("statusAnimationLabel"); // NOI18N

        progressBar.setName("progressBar"); // NOI18N

        javax.swing.GroupLayout statusPanelLayout = new javax.swing.GroupLayout(statusPanel);
        statusPanel.setLayout(statusPanelLayout);
        statusPanelLayout.setHorizontalGroup(
            statusPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(statusPanelSeparator, javax.swing.GroupLayout.DEFAULT_SIZE, 400, Short.MAX_VALUE)
            .addGroup(statusPanelLayout.createSequentialGroup()
                .addContainerGap()
                .addComponent(statusMessageLabel)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 230, Short.MAX_VALUE)
                .addComponent(progressBar, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addComponent(statusAnimationLabel)
                .addContainerGap())
        );
        statusPanelLayout.setVerticalGroup(
            statusPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(statusPanelLayout.createSequentialGroup()
                .addComponent(statusPanelSeparator, javax.swing.GroupLayout.PREFERRED_SIZE, 2, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addGroup(statusPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(statusMessageLabel)
                    .addComponent(statusAnimationLabel)
                    .addComponent(progressBar, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(3, 3, 3))
        );

        setComponent(mainPanel);
        setMenuBar(menuBar);
        setStatusBar(statusPanel);
    }// </editor-fold>                        
        
        
        
    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         

        Clientes cli = em.find(Clientes.class, 1);  //getting the record with id=1 just for the test
        jLabel1.setText(cli.getNombre());        

    }                                        

    // Variables declaration - do not modify                     
    private javax.swing.JButton jButton1;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JTextField jTextField1;
    private javax.swing.JTextField jTextField2;
    private javax.swing.JPanel mainPanel;
    private javax.swing.JMenuBar menuBar;
    private javax.swing.JProgressBar progressBar;
    private javax.swing.JLabel statusAnimationLabel;
    private javax.swing.JLabel statusMessageLabel;
    private javax.swing.JPanel statusPanel;
    // End of variables declaration                   

    private final Timer messageTimer;
    private final Timer busyIconTimer;
    private final Icon idleIcon;
    private final Icon[] busyIcons = new Icon[15];
    private int busyIconIndex = 0;

    private JDialog aboutBox;
    
}

[Martin Frisone]

and forgot the stacktrace

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
        at minuto1.Minuto1View.jButton1ActionPerformed(Minuto1View.java:256)
        at minuto1.Minuto1View.access$800(Minuto1View.java:28)
        at minuto1.Minuto1View$4.actionPerformed(Minuto1View.java:150)
        at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
        at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
        at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
        at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
        at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
        at java.awt.Component.processMouseEvent(Component.java:6263)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3267)
        at java.awt.Component.processEvent(Component.java:6028)
        at java.awt.Container.processEvent(Container.java:2041)
        at java.awt.Component.dispatchEventImpl(Component.java:4630)
        at java.awt.Container.dispatchEventImpl(Container.java:2099)
        at java.awt.Component.dispatchEvent(Component.java:4460)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4574)
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4238)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4168)
        at java.awt.Container.dispatchEventImpl(Container.java:2085)
        at java.awt.Window.dispatchEventImpl(Window.java:2475)
        at java.awt.Component.dispatchEvent(Component.java:4460)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

[Freddy Wong]

Do you run this application in an EJB container? @PersistenceContext can only be used if you use EJB. If you use pure JPA, you need to create the EntityManager by yourself, e.g.

    
EntityManagerFactory emf = Persistence.createEntityManagerFactory("minuto1PU");
EntityManager em = emf.createEntityManager();

[Martin Frisone]

Oh! yes, I see my mistake now... I'm not using an EJB containter just a desktop application, that's why the Container Managed Persistence won't work.

I've tried the Application Managed Persistence and it worked. Problem Solved, thanks a lot