This is the first part of 3 that shows you how to get data from database with JPA 2.0 and display them with JavaFX.
In this first part we are going:
- to create the database and one table
- to create the entity and the persistence.xml file
- to use a namedQuery
- to use criteria query API
Create the database and the table
- Create a derby database with :
- Database Name : javafxDB
- UserName : APP
- Password : paddy
- Create the music table and fill it.
Execute this script to create the music table and fill it The music table has 3 fields: an auto generated id, the name of the artist (artist_name) and the name of the album (album_title) …
And of course, it’s just for an example ;)
The Entity and the persistence unit
- The Entity which is mapped to music table
package paddy.domain;
import java.io.Serializable;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.NamedQuery;
@author
@Entity
@NamedQuery(name = "findAllAlbum", query= "select m from Music m")
public class Music implements Serializable {
@Id
@GeneratedValue
private Long id;
@Column(name = "artist_name")
private String artisteName;
@Column(name = "album_title")
private String albumTitle;
public Music() {
}
@Override
public String toString(){
StringBuffer sb = new StringBuffer();
sb.append("id : ");sb.append(id);sb.append(" ; ");
sb.append("artisteName : ");sb.append(artisteName);sb.append(" ; ");
sb.append("albumTitle : ");sb.append(albumTitle);
sb.append(" \n");
return sb.toString();
}
}
The entity is just a plain old Java object (pojo) with some annotations.
@Entity: designate my pojo as an entity so I can use it with JPA services.
@Id: designate the property as the entity's primary key
@GeneratedValue: used with @Id, it defines that this value is generated automatically
@Column: is used, in my example, to mapped the property of the entity with the field of the table
@NamedQuery(name = "findAllAlbum", query= "select m from Music m") is used to create pre-defined queries which get all record from music table.
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0" xmlns="http://java.sun.com/xml/ns/persistence">
<persistence-unit name="MusicAndLight" transaction-type="RESOURCE_LOCAL">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
<class>paddy.domain.Music</class>
<properties>
<property name="eclipselink.target-database" value="DERBY"/>
<property name="javax.persistence.jdbc.driver" value="org.apache.derby.jdbc.ClientDriver"/>
<property name="javax.persistence.jdbc.url" value="jdbc:derby://localhost:1527/javafxDB"/>
<property name="javax.persistence.jdbc.user" value="APP"/>
<property name="javax.persistence.jdbc.password" value="paddy"/>
</properties>
</persistence-unit>
</persistence>
The persistence.xml file defined:
- the persistence unit named MusicAndLight
- the entity (paddy.domain.Music) managed by the persistence unit
- and how the persistence unit connects to the database
Execute query by using a namedQuery
EntityManagerFactory emf = Persistence.createEntityManagerFactory("MusicAndLight");
EntityManager em = emf.createEntityManager();
Query query = em.createNamedQuery("findAllAlbum");
List<Music> musics = query.getResultList();
for (Music music : musics){
System.out.println(music);
}
em.close();
emf.close();
Execute query by using a criteria API
EntityManagerFactory emf = Persistence.createEntityManagerFactory("MusicAndLight");
EntityManager em = emf.createEntityManager();
String param = "Arc%";
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Music> query2 = cb.createQuery(Music.class);
Root<Music> music2 = query2.from(Music.class);
query2.where(cb.like(music2.<String>get("artisteName"), param));
List<Music> musics2 = em.createQuery(query2).getResultList();
for (Music music : musics2){
System.out.println(music);
}
em.close();
emf.close();
Note: don’t forget to create (in NetBeans) a library containing the jar DerbyClient.jar and being called DerbyClient.
