-
Be sure to configure the supplementary MI Maven
archetypes in your Eclipse IDE.
-
Choose the mi-maven-archetype-quickstart
artifact and create a new project named
“Airline”.
-
Create an Airline @Entity
class inside a xyz.model package:
package de.hdm_stuttgart.mi.persist.airline.model;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
@Entity
public class Airline {
@Id
@GeneratedValue
Long id;
String name;
String icaoCode;
public Airline(final String name, final String icaoCode) {
this.name = name;
this.icaoCode = icaoCode;
}
protected Airline(){}
}
The three imports require additional libraries to be
present. Using Maven this may be achieved by adding the
following dependency to your project's
pom.xml file:
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-entitymanager</artifactId>
<version>5.1.0.Final</version>
</dependency>
Why do we need protected Airline(){}
?
-
Chapter
2 of [Bauer2015] provides hints
starting a project. Rather than using the described more
elaborate JTA based setup you may just
want to follow a simpler JDBC™ based
approach when defining a persistence unit in your project's
src/main/resources/META-INF/persistence.xml
file:
<persistence
version="2.1"
xmlns="http://xmlns.jcp.org/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence
http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
<!--
The <code>persistence.xml</code> file configures at least one persistence unit;
each unit must have a unique name.
-->
<persistence-unit name="AirlinePU">
<!-- A persistent unit has persistent (mapped) classes, you list them here. -->
<class>de.hdm_stuttgart.mi.persist.airline.model.Airline</class>
<!-- Hibernate can scan your classpath for mapped classes and add them automatically
to your persistence unit. This setting disables that feature. -->
<exclude-unlisted-classes>true</exclude-unlisted-classes>
<!-- Standard or vendor-specific options can be set as properties on a persistence unit.
Any standard properties have the <code>javax.persistence</code> name prefix, Hibernate's
settings use <code>hibernate</code> -->
<properties>
<!-- JDBC database connection parameter -->
<property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver"/>
<property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/hdm?useSSL=false"/>
<property name="javax.persistence.jdbc.user" value="hdmuser"/>
<property name="javax.persistence.jdbc.password" value="XYZ"/>
<!-- The JPA engine should drop and re-create the SQL schema in the database
automatically when it boots. This is ideal for automated testing, when
you want to work with a clean database for every test run. -->
<property
name="javax.persistence.schema-generation.database.action"
value="drop-and-create"/>
<!-- When printing SQL in logs, let Hibernate format the SQL nicely and generate
comments into the SQL string so we know why Hibernate executed the SQL statement. -->
<property name="hibernate.format_sql" value="true"/>
<property name="hibernate.use_sql_comments" value="true"/>
<!-- Disable Hibernate scanning completely, we also don't want any hbm.xml files
discovered and added automatically. -->
<property name="hibernate.archive.autodetection" value="none"/>
</properties>
</persistence-unit>
</persistence>
Our persistence unit connecting to a Mysql™ database server requires another
Maven dependency:
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.38</version>
</dependency>
-
Our main() class will just
write a single Airline instance to
the database server:
package de.hdm_stuttgart.mi.persist.airline;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import de.hdm_stuttgart.mi.persist.airline.model.Airline;
public class CreateAirline {
// This requires a corresponding entry <persistence-unit name="AirlinePU">
// in META-INF/persistence.xml
private static final String PERSISTENCE_UNIT_NAME = "AirlinePU";
/**
* @param args Unused
*/
public static void main( String[] args ) {
final EntityManagerFactory factory = Persistence.createEntityManagerFactory(PERSISTENCE_UNIT_NAME);
final EntityManager em = factory.createEntityManager();
em.getTransaction().begin();
final Airline lh = new Airline("Lufthansa", "DLH");
em.persist(lh);
em.getTransaction().commit();
em.close();
factory.close();
}
}
How does the generated Mysql™ database schema look like?
Explain the result.
No. 2
