Question

I am doing a small project using JPA. I need to insert the employee object.
For that when I use the annotated entity manager I got the NullPointer exception.
But when I use the Normal EntityManager without using the annotation it is working fine.
Do I need to configure somewhere else other than persistence.xml to work this examle fine?

Please see the code below.

public class EmployeeDao implements IEmployeeDao{       

     @PersistenceContext(unitName = "timesheet")
    private EntityManager entityManager ;

    @Override
    public boolean createEmployee(IEmployee employee) { 

        this.entityManager.persist(employee);       

        return true;
    }
}

persistence.xml

<?xml version="1.0" encoding="UTF-8" ?>
<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"
    version="2.0" xmlns="http://java.sun.com/xml/ns/persistence">
    <persistence-unit name="timesheet" transaction-type="RESOURCE_LOCAL">       
        <class>com.timesheet.model.Employee</class>     
        <properties>
            <property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" />
            <property name="javax.persistence.jdbc.url"
                value="jdbc:mysql://localhost:3306/timesheet" />
            <property name="javax.persistence.jdbc.user" value="root" />
            <property name="javax.persistence.jdbc.password" value="" />

            <!-- EclipseLink should create the database schema automatically -->
            <property name="eclipselink.ddl-generation" value="create-tables" />
            <property name="eclipselink.ddl-generation.output-mode"
                value="database" />
        </properties>

    </persistence-unit>
</persistence>

Answer 1

Injection of resources (in your case via use of @PersistenceContext) works only in container managed classes (like EJBs and Servlets). This explained with more details for example in Java EE specification v6, EE5.2.5.

What you can do:

• Modify your class so that it is managed class
• move injection of resources to managed class and pass it to
  EmployeeDao,
• use JNDI lookup as before