EnvironmentNote: Make sure the datasource is configured properly. Visit the post (
http://vkslabs.com/adding-mysql-data-store-to-jboss-7-x/) to find out how to configure datasource.
Step 1: Configure persistence.xmlCreate a file called persistence.xml and add the following content
[xml]
<persistence 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"
version="2.0">
<persistence-unit name="testjpa" transaction-type="RESOURCE_LOCAL">
<jta-data-source>java:jboss/datasources/myDS</jta-data-source>
<class>com.test.StudentBean</class>
<properties>
<property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/>
<property name="hibernate.hbm2ddl.auto" value="update"/>
<property name="hibernate.transaction.jta.platform"
value="org.hibernate.service.jta.platform.internal.JBossAppServerJtaPlatform" />
</properties>
</persistence-unit>
</persistence>
[/xml]
Make sure the datasource name matches the datasource configured in JBoss
Step 2: Create your beanCreate the bean which you would like to persist
[java]
package com.test;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
@Entity (name="student")
public class StudentBean {
@Id
@GeneratedValue
private int id;
private String name;
private int age;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
[/java]
- @Entity annotations should be mentioned to denote the bean is a entity bean
- @Id annotation makes the field as primary key of the table
- @GeneratedValue annotation makes the field value as auto generated
Step 3: Persist your bean using EMF[java]
EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("testjpa");
EntityManager em = entityManagerFactory.createEntityManager();
EntityTransaction userTransaction = em.getTransaction();
userTransaction.begin();
StudentBean student = new StudentBean();
student.setName(name);
student.setAge(age);
em.persist(student);
em.flush();
userTransaction.commit();
em.close();
entityManagerFactory.close();
[/java]
- testjpa is the name of persistence-unit in the persistence.xml
- Calling persist() just marks the bean for persistence and might not populate DB immediately, in order to see the data in database immediately flush() must be called.
Note:
- The value for the property hibernate.hbm2ddl.auto can be
validate: validate the schema, makes no changes to the database.
update: update the schema.
create: creates the schema, destroying previous data.
create-drop: drop the schema at the end of the session.
- In case there is no exception when bean is persisted but no row is found in DB then make sure the value for the property hibernate.hbm2ddl.auto is not set to create-drop
- Important: The common mistake the developers make is to create the file in the META-INF folder under the project folder which is wrong.
The META-INF folder where persistence.xml is present should be in classpath but for JPA the root of the persistence unit is the WEB-INF/classes directory
hence the persistence.xml should be copied in to
WEB-INF/classes/META-INF folder (You might have to create META-INF folder manually).
If the persistence.xml is not created in the right folder the following error will be encountered
javax.persistence.PersistenceException: No Persistence provider for EntityManager named testjpa: No META-INF/persistence.xml was found in classpath.
- In case you face the following exception make sure the persistence.xml has the attribute transaction-type="RESOURCE_LOCAL"
ERROR [stderr] (http-localhost-127.0.0.1-8080-1) java.lang.NullPointerException
ERROR [stderr] (http-localhost-127.0.0.1-8080-1) at org.hibernate.engine.transaction.internal.jta.JtaStatusHelper.getStatus(JtaStatusHelper.java:73)
ERROR [stderr] (http-localhost-127.0.0.1-8080-1) at org.hibernate.engine.transaction.internal.jta.JtaStatusHelper.isActive(JtaStatusHelper.java:115)
ERROR [stderr] (http-localhost-127.0.0.1-8080-1) at org.hibernate.engine.transaction.internal.jta.CMTTransaction.join(CMTTransaction.java:149)
ERROR [stderr] (http-localhost-127.0.0.1-8080-1) at org.hibernate.ejb.AbstractEntityManagerImpl.joinTransaction(AbstractEntityManagerImpl.java:1207)
ERROR [stderr] (http-localhost-127.0.0.1-8080-1) at org.hibernate.ejb.AbstractEntityManagerImpl.postInit(AbstractEntityManagerImpl.java:176)
ERROR [stderr] (http-localhost-127.0.0.1-8080-1) at org.hibernate.ejb.EntityManagerImpl.<init>(EntityManagerImpl.java:89)
ERROR [stderr] (http-localhost-127.0.0.1-8080-1) at org.hibernate.ejb.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:125)
ERROR [stderr] (http-localhost-127.0.0.1-8080-1) at org.hibernate.ejb.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:120)
