JPA EntityManager Nullpointer exception (which shouldn't be!?) -

my ejb code:

@stateless public class employeebean {        @persistencecontext(unitname="eclipselink_jpa")       private entitymanager entitymanager;         public void createemployee(){           employee employee = new employee( );            employee.seteid( 1201 );           employee.setename( "gopal" );           employee.setsalary( 40000 );           employee.setdeg( "technical manager" );            entitymanager.persist( employee );           entitymanager.gettransaction( ).commit( );            entitymanager.close( );        } } 

basically, nullpointer exception happens @ line entitymanager.persist called, should not happen right?

my persistence.xml file

<?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="eclipselink_jpa" transaction-type="resource_local">        <class>com.jpa.beans.employee</class>        <properties>          <property name="javax.persistence.jdbc.url" value="jdbc:hsqldb:file:e:\hqldb_aj"/>          <property name="javax.persistence.jdbc.user" value="sa"/>          <property name="javax.persistence.jdbc.password" value="password"/>          <property name="javax.persistence.jdbc.driver" value="org.hsqldb.jdbc.jdbcdriver"/>          <property name="eclipselink.logging.level" value="fine"/>          <property name="eclipselink.ddl-generation" value="create-tables"/>       </properties>     </persistence-unit> </persistence> 

i have eclipselink.jar , other eclipselink jpa jars in class path.

here entity beans:

@entity @table public class employee {     @id    @generatedvalue(strategy = generationtype.auto)       private int eid;    private string ename;    private double salary;    private string deg;     public employee(int eid, string ename, double salary, string deg) {       super( );       this.eid = eid;       this.ename = ename;       this.salary = salary;       this.deg = deg;    }     public employee( ) {       super();    }     public int geteid( ) {       return eid;    }     public void seteid(int eid) {       this.eid = eid;    }     public string getename( ) {       return ename;    }     public void setename(string ename) {       this.ename = ename;    }     public double getsalary( ) {       return salary;    }     public void setsalary(double salary) {       this.salary = salary;    }     public string getdeg( ) {       return deg;    }     public void setdeg(string deg) {       this.deg = deg;    }     @override    public string tostring() {       return "employee [eid=" + eid + ", ename=" + ename + ", salary=" + salary + ", deg=" + deg + "]";    } } 

whats seems problem? can help? ive been figuring out of day now.

problem solved: shouldn't using resource local because running in app server. anyway. appreciated

when set transaction-type="resource_local" in persistence.xml config file, means (=your application's code) take care of creating entitymanager , handle transactions yourself. in such case can demand injected underlying container entitymanagerfactory , can using @persistenceunit annotation. on such object call createentitymanager() gives entitymanager.

if want use entitymanager supplied container must specify transaction-type="jta". annotate entitymanager in code, , not care of creating, committing or rolling transaction. done container use jta transaction , decide when create, commit or rollback it.

those 2 ways commonly known respectively application managed entitymanager , container managed entitymanager

you can find more details on how work each of 2 ways of handling transactions here or here