JPA-Eclipselink does not work. "AbstractSession is null"

Question

I am new in jpa. I am using eclipselink for that. So i am trying to a simple maven project. But it doesnt work. I am getting this error (full stack trace):

Internal Exception: java.lang.NullPointerException: Cannot invoke "org.eclipse.persistence.internal.sessions.AbstractSession.getName()" because "this.session" is null
    at org.eclipse.persistence.exceptions.PersistenceUnitLoadingException.exceptionSearchingForPersistenceResources(PersistenceUnitLoadingException.java:127)
    at org.eclipse.persistence.jpa.PersistenceProvider.createEntityManagerFactoryImpl(PersistenceProvider.java:115)
    at org.eclipse.persistence.jpa.PersistenceProvider.createEntityManagerFactory(PersistenceProvider.java:188)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:79)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:54)
    at main.Main.main(Main.java:16)
Caused by: java.lang.NullPointerException: Cannot invoke "org.eclipse.persistence.internal.sessions.AbstractSession.getName()" because "this.session" is null
    at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.predeploy(EntityManagerSetupImpl.java:2027)
    at org.eclipse.persistence.internal.jpa.deployment.JPAInitializer.callPredeploy(JPAInitializer.java:100)
    at org.eclipse.persistence.jpa.PersistenceProvider.createEntityManagerFactoryImpl(PersistenceProvider.java:104)

My main class:

package main;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;

import dao.PersonDao;
import model.JpaPerson;

public class Main {

    public static void main(String[] args) {
        
         
        EntityManagerFactory factory = Persistence.createEntityManagerFactory("JpaPersonUnit");// block 16. Exception coming from there

        EntityManager manager = factory.createEntityManager();
        EntityTransaction transaction=manager.getTransaction();
        
        PersonDao pd=new PersonDao(manager);
        
        
        transaction.begin();
        JpaPerson person1=new JpaPerson(0, "Efe", "Yanıkkollu", "Büyük Efe İmparatorluğu");
        JpaPerson person2=new JpaPerson(1, "Yavuz Selim", "Yanıkkollu", "Türkiye");
        
        pd.create(person3);
        pd.create(person2);
        pd.create(person1);
        
        transaction.commit();
        
        System.out.println(pd.getPersonById(2).getName());
        
        transaction.begin();
        pd.delete(person3);
        transaction.commit();
        
        int count=0;
        for(JpaPerson p : pd.read()) {
            System.out.println("Name: " + p.getName());
            count ++;
        }
        System.out.println(count);
    }
}

my persistence.xml (in META-INF):

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.2" xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_2.xsd">
    <persistence-unit name="JpaPersonUnit">
    
    <class>model.JpaPerson</class>
    
    <properties>
            <property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" />
            <property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/jpa.schema?serverTimezone=UTC" />
            <property name="javax.persistence.jdbc.user" value="root" />
            <property name="javax.persistence.jdbc.password" value="12345" />
            <property name="eclipselink.ddl-generation" value="drop-and-create-tables" />
        
            <property name="eclipselink.logging.level" value="ALL"/>
           
        </properties>
    
    
    
    
    </persistence-unit>
</persistence>

my pom.xml:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>EclipseLink01</groupId>
  <artifactId>EclipseLink01</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  
  
  <properties>
        <eclipselink.version>2.6.4</eclipselink.version>
        <mysql.version>6.0.4</mysql.version>
    </properties>

    <dependencies>
    
        <dependency>
            <groupId>org.eclipse.persistence</groupId>
            <artifactId>eclipselink</artifactId>
            <version>${eclipselink.version}</version>
        </dependency>
        
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>${mysql.version}</version>
        </dependency>

    </dependencies>
  
</project>

there is nothing wrong with the structure of my entity class. And jpa.schema is exist on mysql. I have also received this error before when I wanted to run another jpa project. What should I do to fix this?

You have logging on 'all', is there anything being written out by EclipseLink? — Chris, Sep 26 '22 at 17:46

score 0 · Answer 1 · answered Sep 26 '22 at 17:45

Your persistence.xml is missing a few points, specifically the transaction type (resource local if outside a container) and the provider. See the oracle docs for a good example, but you might try:

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.2" xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_2.xsd">
    <persistence-unit name="JpaPersonUnit" transaction-type="RESOURCE_LOCAL">
    <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
    <exclude-unlisted-classes>false</exclude-unlisted-classes>
    
    <properties>
            <property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" />
            <property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/jpa.schema?serverTimezone=UTC" />
            <property name="javax.persistence.jdbc.user" value="root" />
            <property name="javax.persistence.jdbc.password" value="12345" />
            <property name="eclipselink.ddl-generation" value="drop-and-create-tables" />
        
            <property name="eclipselink.logging.level" value="ALL"/>
        </properties>
    </persistence-unit>
</persistence>

JPA-Eclipselink does not work. "AbstractSession is null"

1 Answers1