EntityManager problem (nullPointer exception)

Question

Hello,
I need help.
I have created Entity from Table (table Users) from MySQL database.
I'm using JPA.
@Entity
@NamedQueries( { @NamedQuery(name = "Users.findAll", query = "select o from Users o"),
                 @NamedQuery(name = "Users.findByUsername", query = "SELECT o FROM Users o WHERE o.username = :username")})
@Table(name = "\"users\"")
public class Users implements Serializable {
    @SuppressWarnings("compatibility:-1756790181151554415")
    private static final long serialVersionUID = 1L;
    @Column(name = "address", nullable = false)
    private String address;
    @Column(name = "city", nullable = false)
    private String city;
    @Column(name = "email", nullable = false)
    private String email;
    @Column(name = "firstPassword", nullable = false)
    private String firstPassword;
    @Column(name = "firstname", nullable = false)
    private String firstname;
    @Column(name = "lastname", nullable = false)
    private String lastname;
    @Column(name = "rank", nullable = false)
    private int rank;
    @Temporal(TemporalType.DATE)
    @Column(name = "regdate", nullable = false)
    private Date regdate;
    @Id
    @Column(name = "user_id", nullable = false)
    private long user_id;
    @Column(name = "username", nullable = false)
    private String username;
    public Users() {
    public Users(String address, String city, String email, String firstPassword, String firstname, String lastname,
                 int rank, Date regdate, long user_id, String username) {
        this.address = address;
        this.city = city;
        this.email = email;
        this.firstPassword = firstPassword;
        this.firstname = firstname;
        this.lastname = lastname;
        this.rank = rank;
        this.regdate = regdate;
        this.user_id = user_id;
        this.username = username;
    public String getAddress() {
        return address;
    public void setAddress(String address) {
        this.address = address;
    public String getCity() {
        return city;
    public void setCity(String city) {
        this.city = city;
    public String getEmail() {
        return email;
    public void setEmail(String email) {
        this.email = email;
    public String getFirstPassword() {
        return firstPassword;
    public void setFirstPassword(String firstPassword) {
        this.firstPassword = firstPassword;
    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 int getRank() {
        return rank;
    public void setRank(int rank) {
        this.rank = rank;
    public Date getRegdate() {
        return regdate;
    public void setRegdate(Date regdate) {
        this.regdate = regdate;
    public long getUser_id() {
        return user_id;
    public void setUser_id(long user_id) {
        this.user_id = user_id;
    public String getUsername() {
        return username;
    public void setUsername(String username) {
        this.username = username;
}and I have created ManagedBean LoginUser. In this class is method getUser().
        private Users getUser() {
            System.out.println("Username: " +username);
            try{
                Users userr = (Users) entManager.createNamedQuery("Users.findByUsername").setParameter("username", username).getSingleResult();
                loginUser.user = userr;
                System.out.println("USER---- " +userr);
                return userr;
            }catch(NoResultException nre){
                System.out.println(nre.getMessage());
                return null;
        }I have problem with entity manager because this row: Users userr = (Users) entManager.createNamedQuery("Users.findByUsername").setParameter("username", username).getSingleResult();* causes exception:
Caused by: java.lang.NullPointerException
     at view.loginUser.getUser(loginUser.java:74)
        .I don't know why. This code is from my previous project from netbeans and there wasn't a problem.
I don't see a problem.
Can you help me ?
Sorry for my English.
Thanks.

Answer 1

Does the persistence.xml define the persistence-unit ViewController? What is the persistence provider? Hibernate or Eclipselink? Is a datasource with MySQL deifned?
With the EclipseLink provider the persistence.xml should be similar to the following.
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0"
     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_2_0.xsd">
     <persistence-unit name="ViewController" transaction-type="JTA">
          <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
          <jta-data-source>java:jboss/datasources/MySQLDS</jta-data-source>
          <class>packagename.Users</class>
          <properties>
               <property name="eclipselink.target-server" value="WebLogic_10"/>
               <property name="eclipselink.target-database" value="MySQL"/>
               <property name="eclipselink.ddl-generation" value="create-tables"/>
               <property name="eclipselink.logging.level" value="FINEST"/>
               <property name="eclipselink.dialect" value="org.hibernate.dialect.MySQLDialect" />
          </properties>
     </persistence-unit>
</persistence>
Edited by: dvohra16 on Feb 25, 2013 9:36 AM