Hibernate: Automatically creating/updating the db tables based on entity classes

Question

I have the following entity class (in Groovy):

import javax.persistence.Entity
import javax.persistence.Id
import javax.persistence.GeneratedValue
import javax.persistence.GenerationType

@Entity
public class ServerNode {

  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  Long id

  String firstName
  String lastName


}

and my persistence.xml:

<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence" version="1.0">

    <persistence-unit name="NewPersistenceUnit">
        <provider>org.hibernate.ejb.HibernatePersistence</provider>
        <properties>
            <property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/Icarus"/>
            <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
            <property name="hibernate.connection.username" value="root"/>
            <property name="hibernate.connection.password" value=""/>
            <property name="hibernate.archive.autodetection" value="class"/>
            <property name="hibernate.show_sql" value="true"/>
            <property name="hibernate.format_sql" value="true"/>
            <property name="hbm2ddl.auto" value="create"/>
        </properties>
        <class>net.interaxia.icarus.data.models.ServerNode</class>
    </persistence-unit>
</persistence>

and the script:

import javax.persistence.EntityManager
import javax.persistence.EntityManagerFactory
import javax.persistence.Persistence
import net.interaxia.icarus.data.models.ServerNode

def factory = Persistence.createEntityManagerFactory("NewPersistenceUnit")
def manager = factory.createEntityManager()

manager.getTransaction().begin()

manager.persist new ServerNode(firstName: "Test", lastName: "Server")

manager.getTransaction().commit()

the database 'Icarus' exists, but currently has no tables. I would like Hibernate to automatically create and/or update the tables based on the entity classes. How would i accomplish this?

Answer 1

You might try changing this line in your persistence.xml from

<property name="hbm2ddl.auto" value="create"/>

to:

<property name="hbm2ddl.auto" value="update"/>

This is supposed to maintain the schema to follow any changes you make to the Model each time you run the app.

Got this from JavaRanch

Answer 2

i tried that and get this error:

2006 [main] WARN org.hibernate.util.JDBCExceptionReporter - SQL Error: 1146, SQLState: 42S02
2006 [main] ERROR org.hibernate.util.JDBCExceptionReporter - Table 'icarus.servernode' doesn't exist
Caught: javax.persistence.PersistenceException: org.hibernate.exception.SQLGrammarException: could not insert: [net.interaxia.icarus.data.models.ServerNode]
    at PopulateServerNodes.run(PopulateServerNodes.groovy:18)
    at PopulateServerNodes.main(PopulateServerNodes.groovy)

Answer 3

I don't know if leaving hibernate off the front makes a difference.

The reference suggests it should be hibernate.hbm2ddl.auto

A value of create will create your tables at sessionFactory creation, and leave them intact.

A value of create-drop will create your tables, and then drop them when you close the sessionFactory.

Perhaps you should set the javax.persistence.Table annotation explicitly?

Hope this helps.