Hello World with standalone Java Persistence, Hibernate and HSQLDB

Lately just started reading (& learning) EJB3. Because of a slow PC at home, I needed to be able to run code for the Java Persistence API in the standalone mode, without the overhead of a huge database or app server. So, I rustled up this guide to get up and running with Java Persistence. Basically all you need is a database and an implementation of the persistence API. We will use HSQL and Hibernate Entity Manager respectively. Hibernate Entity Manager runs on the Hibernate core, so will need that too.

Step 1: You will need Java 5. Get it from http://java.sun.com

Step 2: Download HQSLDB from http://hsqldb.org. Extract into some folder (eg. D:\hsqldb)

Step 3: Download the Hibernate Entity Manager from http://hibernate.org. Extract into some folder. (eg. D:\hibernate-entitymanager-3.2.1.GA)

Step 4: Download the Hibernate Core from http://hibernate.org. Extract into some folder. (eg. D:\hibernate-3.2)

Step 5: Set up the database

• Create a new folder for all database related files we will create in this step. Lets call it 'db_stuff'.

• Create a server.properties file. We will name our database 'think'. Configuration parameters should be as below:

server.database.0 file:./think
server.dbname.0 think

• Start the database in the server mode by running the following from the command line (Better still put this in a batch file)

java -cp D:\hsqldb\lib\hsqldb.jar org.hsqldb.Server

• You can use the HSQLDB DatabaseManager to view this database. Run the following from the command line to invoke the tool.

java -cp D:\hsqldb\lib\hsqldb.jar org.hsqldb.util.DatabaseManager

In the "Connect" dialog, select the following options:
Type: HSQL Database Engine Server
Driver: org.hsqldb.jdbcDriver
URL: jdbc:hsqldb:hsql://localhost/think
User: sa
Password:

Step 6: Now the standalone. Add the following jars to your project classpath:

• hsqldb.jar from D:\hsqldb\lib\hsqldb.jar
• hibernate3.jar from D:\hibernate-3.2
• all jars from D:\hibernate-3.2\lib\
• hibernate-entitymanager.jar from D:\hibernate-entitymanager-3.2.1.GA
• all jars from D:\hibernate-entitymanager-3.2.1.GA
• Whew!

Step 7: Create the persistence configuration

Create a file named persistence.xml, the persistence configuration file. This file needs to be within a META-INF folder in your classpath. If you are compiling all your classes into a folder, say 'classes', create a META-INF folder under 'classes', then create the persistence.xml file in META-INF. The file should look like below:

<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" version="1.0">

<persistence-unit name="think" transaction-type="RESOURCE_LOCAL">
<properties>
<property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
<property name="hibernate.hbm2ddl.auto" value="update"/>
<property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/>
<property name="hibernate.connection.username" value="sa"/>
<property name="hibernate.connection.password" value=""/>
<property name="hibernate.connection.url" value="jdbc:hsqldb:hsql://localhost/think"/>
</properties>
</persistence-unit>
</persistence>

Note that the transaction-type is RESOURCE_LOCAL. This is required for standalone environments. Also note the "hibernate.connection.url" matches the URL you use to connect from the HSQL DB Manager to the database, jdbc:hsqldb:hsql://localhost/think

Step 8: Create an entity class, BroadcastMessage.java

package com.blogspot.thought_bytes;

import javax.persistence.Entity;
import javax.persistence.Id;

@Entity
public class BroadcastMessage {

@Id
private long id;

private String message;

public long getId() {
return id;
}

public void setId(long id) {
this.id = id;
}

public String getMessage() {
return message;
}

public void setMessage(String message) {
this.message = message;
}
}

Step 9: Create a harness to interact with the persistence layer, ClientHarness.java

package client;

import com.blogspot.thought_bytes.BroadcastMessage;

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


public class ClientHarness {

public static void main(String[] args) {
//Use the persistence.xml
EntityManagerFactory emf = Persistence.createEntityManagerFactory("think");
EntityManager em = emf.createEntityManager();

//
EntityTransaction tx = em.getTransaction();
tx.begin();

//Create and initialize an entity instance
BroadcastMessage mb = new BroadcastMessage();
mb.setId(1);
mb.setMessage("Hello World");

//Persist using the entity manager
em.persist(mb);

//Save
tx.commit();

em.close();
emf.close();

}
}

Run the above.

Go back to the database manager and refresh the view. You should be able to see a new tabel "broadcastmessage". If you query this table you should get the following:

ID MESSAGE
-- -------
1 Hello World

That's it! And now the real hard work begins... :)

Cheers,
Aldrin