Have you ever wanted to test some JPA functionality? Were you discouraged to do so because of the long setup process?
I wanted to test some JPA functionality without the hassle of setting up a DB and configuring XML files, A simple, short piece of code that I was able to run immediately.
This can be done very easily with in-memory HSQLDB and configuration using annotations. You only need Hibernate and HSQLDB on your classpath.
Take a look:
package jpa;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.List;
import javax.persistence.Entity;
import javax.persistence.EntityManager;
import javax.persistence.EntityTransaction;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import org.hibernate.ejb.Ejb3Configuration;
@Entity
public class SimpleEntityTest
{
@Id
@GeneratedValue
private Long id;
private String name;
public SimpleEntityTest()
{
}
public Long getId()
{
return id;
}
public void setId( Long id )
{
this.id = id;
}
public String getName()
{
return name;
}
public void setName( String name )
{
this.name = name;
}
@SuppressWarnings("unchecked")
public static void main( String[] args ) throws Exception
{
Ejb3Configuration cfg = new Ejb3Configuration();
cfg.setProperty( "hibernate.connection.driver_class", "org.hsqldb.jdbcDriver" );
cfg.setProperty( "hibernate.connection.username", "sa" );
cfg.setProperty( "hibernate.connection.password", "" );
cfg.setProperty( "hibernate.connection.url", "jdbc:hsqldb:mem:test" );
cfg.setProperty( "hibernate.dialect", "org.hibernate.dialect.HSQLDialect" );
cfg.setProperty("hibernate.hbm2ddl.auto", "create-drop" );
cfg.addAnnotatedClass( SimpleEntityTest.class );
EntityManager em = cfg.buildEntityManagerFactory().createEntityManager();
System.out.println( "create the entity" );
EntityTransaction trx = em.getTransaction();
trx.begin();
SimpleEntityTest ent = new SimpleEntityTest();
ent.setName( "test" );
em.persist( ent );
trx.commit();
System.out.println( "change the entity" );
trx = em.getTransaction();
trx.begin();
List entlist = em.createQuery( "from " + SimpleEntityTest.class.getName() ).getResultList();
for ( Object object : entlist )
{
SimpleEntityTest ent1 = (SimpleEntityTest)object;
ent1.setName( "other" );
}
trx.commit();
// check with a connection that is not managed by Hibernate
Connection con = DriverManager.getConnection( "jdbc:hsqldb:mem:test", "sa", "" );
Statement stmt = con.createStatement();
ResultSet rs = stmt.executeQuery( "select name from " + SimpleEntityTest.class.getSimpleName() );
while ( rs.next() )
{
System.out.println( "Entity name: " + rs.getString( 1 ) );
}
rs.close();
stmt.close();
con.close();
}
}
Even if you don't have anything installed you can be up and running in minutes using Maven (assuming you have Maven installed and working).
Follow 4 simple steps:
Create a Maven project: mvn archetype:create -DarchetypeGroupId=org.apache.maven.archetypes -DgroupId=jpa -DartifactId=jpa-test
Copy the above class to jpa-test/src/main/java/jpa
