Hibernate basic example with Apache Derby and Maven

We’re going to make a really easy test with Hibernate in our laptop. First, we’re going to configure an Apache Derby database. We are using Spring STS as our prefered IDE. Besides we will add Maven for our project’s dependencies .Configuring Hibernate in STS with Maven is an easy task. You only need to add your needings dependencies to our pom.xml file and start to coding.

With Maven you can always configure your repositories where you want to load your dependencies through your settings.xml file (it is saved within the conf directory of your Maven installation path.
To look for your requiered dependencies, STS or Eclipse have a special editor for the pom files from where you can find and add your requiered dependencies in your project. If we know that we are going to need a determined class o we want to know how many jar versions there are, I recommend going to the next two websites: mvnrepository and jarvana. The second one is really useful because you can look for a specified class, project or content. Our pom.xml file could have the following aspect:

<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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.hop2croft.pruebas.hibernate</groupId>
	<artifactId>pruebasHibernate</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<repositories>
		<repository>
			<id>jboss</id>
			<url>http://repository.jboss.org/maven2</url>
		</repository>
	</repositories>
	<dependencies>
		<dependency>
			<groupId>org.hibernate</groupId>
			<artifactId>hibernate</artifactId>
			<version>3.5.1-Final</version>
			<type>pom</type>
		</dependency>
		<dependency>
			<groupId>org.hibernate</groupId>
			<artifactId>hibernate-annotations</artifactId>
			<version>3.5.5-Final</version>
		</dependency>
		<dependency>
			<groupId>org.hibernate</groupId>
			<artifactId>hibernate-entitymanager</artifactId>
			<version>3.5.5-Final</version>
		</dependency>
		<dependency>
			<groupId>antlr</groupId>
			<artifactId>antlr</artifactId>
			<version>2.7.6</version>
		</dependency>
		<dependency>
			<groupId>commons-collections</groupId>
			<artifactId>commons-collections</artifactId>
			<version>3.2.1</version>
		</dependency>
		<dependency>
			<groupId>dom4j</groupId>
			<artifactId>dom4j</artifactId>
			<version>1.6.1</version>
		</dependency>
		<dependency>
			<groupId>javassist</groupId>
			<artifactId>javassist</artifactId>
			<version>3.9.0.GA</version>
		</dependency>
		<dependency>
			<groupId>javax.transaction</groupId>
			<artifactId>jta</artifactId>
			<version>1.1</version>
		</dependency>
		<dependency>
			<groupId>org.slf4j</groupId>
			<artifactId>slf4j-api</artifactId>
			<version>1.5.8</version>
			<type>pom</type>
			<scope>compile</scope>
		</dependency>
		<dependency>
			<groupId>org.hibernate</groupId>
			<artifactId>ejb3-persistence</artifactId>
			<version>3.3.2.Beta1</version>
		</dependency>
		<dependency>
			<groupId>org.slf4j</groupId>
			<artifactId>slf4j-simple</artifactId>
			<version>1.5.8</version>
		</dependency>
		<dependency>
			<groupId>org.apache.derby</groupId>
			<artifactId>derby</artifactId>
			<version>10.7.1.1</version>
		</dependency>
		<dependency>
			<groupId>org.apache.derby</groupId>
			<artifactId>derbyclient</artifactId>
			<version>10.7.1.1</version>
		</dependency>
		<dependency>
			<groupId>org.apache.derby</groupId>
			<artifactId>derbynet</artifactId>
			<version>10.7.1.1</version>
		</dependency>
		<dependency>
			<groupId>org.apache.derby</groupId>
			<artifactId>derbytools</artifactId>
			<version>10.7.1.1</version>
		</dependency>
		<dependency>
			<groupId>javax.security</groupId>
			<artifactId>jacc</artifactId>
			<version>1.0</version>
			<type>jar</type>
			<scope>compile</scope>
		</dependency>
	</dependencies>
	<build>
		<plugins>
			<plugin>
				<artifactId>maven-compiler-plugin</artifactId>
				<configuration>
					<source>1.6</source>
					<target>1.6</target>
				</configuration>
			</plugin>
		</plugins>
	</build>
</project>

One of the things I like most about using Maven is that you can either work with your favourite IDE or work from command line. This feature allows you to compile, package in a jar o run in an application server even if you don’t use a IDE.
We have create a new project STS and we have added the requiered dependencies to work with Hibernate. Now we are going to install Apache Derby in our computer. We download and install Derby from its website. We have to add several enviroment variables to our /etc/profiles file.

export DERBY_INSTALL=/Applications/Apache/db-derby-10.7.1.1
export DERBY_HOME=/Applications/Apache/db-derby-10.7.1.1
export CLASSPATH=$DERBY_INSTALL/lib/derby.jar:$DERBY_INSTALL/lib/derbytools.jar:$CLASSPATH

Apache gives us the posibility of installing an Eclipse plug-in to deal with Derby. In my case I’ve prefered working with Derby from command line. We can see the Derby info once we have installed it in our computer.

ew-host:bin hop2croft$ java org.apache.derby.tools.sysinfo
----------------- Informaci?n de Java ----------------
Versi?n de Java:     1.6.0_24
Proveedor de Java:   Apple Inc.
Inicio Java:         /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home
Classpath de Java:   /Applications/Apache/db-derby-10.7.1.1/lib/derby.jar:/Applications/Apache/db-derby-10.7.1.1/lib/derbytools.jar:.java
Nombre del SO:       Mac OS X
Arquitectura del SO: x86_64
Versi?n del SO:      10.5.8
Nombre usuario Java: hop2croft
Dir. inicial usuario:/Users/hop2croft
Dir. usuario:        /Applications/Apache/db-derby-10.7.1.1/bin
java.specification.name: Java Platform API Specification
java.specification.version: 1.6
java.runtime.version: 1.6.0_24-b07-334-9M3326
--------- Informaci?n de Derby --------
JRE - JDBC: Java SE 6 - JDBC 4.0
[/Applications/Apache/db-derby-10.7.1.1/lib/derby.jar] 10.7.1.1 - (1040133)
[/Applications/Apache/db-derby-10.7.1.1/lib/derbytools.jar] 10.7.1.1 - (1040133)
------------------------------------------------------
-------------- Informaci?n de entorno local ----------
Entorno local actual:  [espa?ol/Espa?a [es_ES]]

After that we have to run our server from command line as well:

$ java -jar derbyrun.jar server start
Sat Apr 16 23:54:17 CEST 2011 : Se ha instalado el administrador de seguridad utilizando la directiva de seguridad de servidores b?sica.
Sat Apr 16 23:54:19 CEST 2011 : Apache Derby Network Server - 10.7.1.1 - (1040133) se ha iniciado y está listo para aceptar conexiones en el puerto 1527

and the ij client:

$ ./ij
Versi?n ij 10.7
ij>

From the client we can create a new database in the database server:

$ ./ij
Versi?n ij 10.7
ij> connect 'jdbc:derby://localhost:1527/BDejemplo;create=true;user=hop2croft;password=hop2croft';

If you prefer not to use the command line client there are several options. You can either install an Eclipse plug-in or a sql graphic client as sql developer or squirrel. I recommend using the second one because it is fully compatible with Hibernate .
The first thing we are going to do is creating the hibernate.cfg.xml file. It indicates how our application is going to connect to our created database.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
	"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
	<hibernate-configuration>
		<session-factory>
			<property name="connection.driver_class">
				org.apache.derby.jdbc.EmbeddedDriver
			</property>
			<property name="connection.url">jdbc:derby://localhost:1527/BDejemplo</property>
			<property name="connection.username">hop2croft</property>
			<property name="connection.password">hop2croft</property>
			<property name="dialect">org.hibernate.dialect.DerbyDialect</property>
			<property name="hibernate.generate_statistics">true</property>
			<property name="show_sql">true</property>
			<mapping resource="com/hibernate/entities/Coche.hbm.xml"/>
		</session-factory>
	</hibernate-configuration>

The show_sql propert allows us to see the sql queries that Hibernate use in our Derby database. The last entry in our hibernate config file indicates the resource we want to map. Now we map every single table from our database. In our case this file will be named as Coche.hbm.xml:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
	<hibernate-mapping package="com.hibernate.entities">
		<class name="Coche" table="Coche">
			<id name="modelo" type="string" column="modelo"></id>
			<property name="marca" type="string" column="marca"></property>
			<property name="precio" type="int" column="precio"></property>
		</class>
	</hibernate-mapping>

We can use annontations too:

@Entity
@Table (name="coche")
public class Coche {
	@Column (name="modelo")
	@Id
	private String modelo;
	@Column (name="marca")
	private String marca;
	@Column (name="precio")
	private int precio;
        // getters y setters
        ...

The next thing will be creating a DAO for quering the database. In our case we are going to implement a method to get all the cars we have in our database. Hibernate has an entity manager that deals with transactions.

	public List<Coche> readFromManager(){
		EntityManager manager = SessionManager.getEntityManager();
		EntityTransaction tran = manager.getTransaction();
		tran.begin();
		Query query = manager.createQuery("select b from Coche b");
		List<Coche> coches = query.getResultList();
		tran.commit();
		manager.close();
		return coches;
	}

Our DAO (data access object) is ready to be used. All we have to do is create a service to use it. Our output could be like this:

Hibernate: select coche0_.modelo as modelo0_0_, coche0_.marca as marca2_0_0_, coche0_.precio as precio0_0_ from Coche coche0_ where coche().modelo=?
Modelo: A6
Marca:   Audi
Precio:   8
-------------------------------------
Hibernate: select coche0_.modelo as modelo0_0_, coche0_.marca as marca2_0_0_, coche0_.precio as precio0_0_ from Coche coche0_ where coche().modelo=?
5887 [main] INFO org.hibernate.stat.Statistics - HQL: from Book, time: 15ms, rows: 2
Modelo: Carrera
Marca:   Porche
Precio:   6
-------------------------------------
5893 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - Logging statistics....
5893 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - start time: 1302994741433
5893 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - sessions opened: 1
5894 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - sessions closed: 0
5894 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - transactions: 0
5894 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - successful transactions: 0
5894 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - optimistic lock failures: 0
5894 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - flushes: 0
5894 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - connections obtained: 2
5894 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - statements prepared: 2
5894 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - statements closed: 2
5894 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - second level cache puts: 0
5894 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - second level cache hits: 0
5894 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - second level cache misses: 0
5894 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - entities loaded: 2
5894 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - entities updated: 0
5894 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - entities inserted: 0
5894 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - entities deleted: 0
5894 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - entities fetched (minimize this): 0
5894 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - collections loaded: 0
5894 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - collections updated: 0
5895 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - collections removed: 0
5895 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - collections recreated: 0
5895 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - collections fetched (minimize this): 0
5895 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - queries executed to database: 1
5895 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - query cache puts: 0
5895 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - query cache hits: 0
5895 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - query cache misses: 0
5895 [main] INFO org.hibernate.stat.ConcurrentStatisticsImpl - max query time: 15ms

In our Hibernate configuration file we have the option of showing data access, queries or sessiones created using statistics. It is really useful if we want to improve our application.

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