Inserting the record into Database through JPA

java, jpa

Solution

I think that you missed the point of JPA. With JPA, you're not supposed to write queries to insert, update or delete persistent objects, JPA will generate them for you. So, what you need to do is to create domain objects and to annotate them to make them "persistable" (such annotated objects are called entities) and tell the JPA engine how to "map" them to your database. Let me try to show you the right path...

First, create a `Voter` domain object and add JPA annotations (an entity class must be annotated with the `Entity` annotation, must have a no-arg constructor, must implement `Serializable`, must have a primary key identified by the `Id` annotation):

@Entity
public class Voter implements Serializable {
    private Long id;
    private String firstName;
    private String lastName;
    private String password;
    // other attributes

    // No-arg constructor
    public Voter() {}

    @Id @GeneratedValue // property access is used
    public Long getId()  { return this.id; }
    protected void setId(Long id)  { this.id = id; }

    // other getters, setters, equals, hashCode
}

I'm using JPA's defaults here (default table name, column name, etc). But this can be customized using the `Table` or `Column` annotations if you need to map your entity to an existing model.

Then, create a new instance and set the various attributes:

Voter voter = new Voter();
voter.setFirstName(firstName);
voter.setLastName(lastName);
...

And persist it:

em.getTransaction().begin();
em.persist(voter);
em.getTransaction().commit();

This is just a short introduction, JPA can't be covered in one answer. To go further, I suggest to check the Introduction to the Java Persistence API from the Java EE 5 Tutorial.

Update: In a managed component, for example an EJB, the `EntityManager` is typically injected and transactions are managed by the container (i.e. you don't explicitly call `begin/commit`). In your case, my bet is that the `EntityManager` isn't successfully injected and calling any method on it results in a NPE. But that's just a guess, you need to provide more details. What is the line 39 of your EJB? How is the `EntityManager` annotated? What does your `persistence.xml` looks like? Please update your question with the relevant details.

Problem

Original source