Java/JPA/EmbeddedId
Embedded Compound Primary Key
<source lang="java">
File: Professor.java import javax.persistence.EmbeddedId; import javax.persistence.Entity; @Entity public class Professor {
@EmbeddedId private ProfessorId id; private String name; private long salary; public Professor() { } public Professor(String country, int id) { this.id = new ProfessorId(country, id); } public int getId() { return id.getId(); } public String getCountry() { return id.getCountry(); } public String getName() { return name; } public void setName(String name) { this.name = name; } public long getSalary() { return salary; } public void setSalary(long salary) { this.salary = salary; } public String toString() { return "Professor id: " + getId() + " name: " + getName() + " country: " + getCountry(); }
}
File: ProfessorId.java import java.io.Serializable; import javax.persistence.Column; import javax.persistence.Embeddable; @Embeddable public class ProfessorId implements Serializable{
private String country; @Column(name = "EMP_ID") private int id; public ProfessorId() { } public ProfessorId(String country, int id) { this.country = country; this.id = id; } public String getCountry() { return country; } public int getId() { return id; } public boolean equals(Object o) { return ((o instanceof ProfessorId) && country.equals(((ProfessorId) o).getCountry()) && id == ((ProfessorId) o) .getId()); } public int hashCode() { return country.hashCode() + id; }
}
File: ProfessorService.java import java.util.Collection; import javax.persistence.EntityManager; import javax.persistence.Query; public class ProfessorService {
protected EntityManager em; public ProfessorService(EntityManager em) { this.em = em; } public Professor createProfessor(String country, int id, String name, long salary) { Professor emp = new Professor(country, id); emp.setName(name); emp.setSalary(salary); em.persist(emp); return emp; } public Professor findProfessor(String country, int id) { return (Professor) em.createQuery( "SELECT e FROM Professor e WHERE e.id.country = ?1 AND e.id.id = ?2") .setParameter(1, country).setParameter(2, id).getSingleResult(); } public Collection<Professor> findAllProfessors() { Query query = em.createQuery("SELECT e FROM Professor e"); return (Collection<Professor>) query.getResultList(); }
}
File: JPAUtil.java import java.io.Reader; import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.ResultSetMetaData; import java.sql.Statement; public class JPAUtil {
Statement st; public JPAUtil() throws Exception{ Class.forName("org.hsqldb.jdbcDriver"); System.out.println("Driver Loaded."); String url = "jdbc:hsqldb:data/tutorial"; Connection conn = DriverManager.getConnection(url, "sa", ""); System.out.println("Got Connection."); st = conn.createStatement(); } public void executeSQLCommand(String sql) throws Exception { st.executeUpdate(sql); } public void checkData(String sql) throws Exception { ResultSet rs = st.executeQuery(sql); ResultSetMetaData metadata = rs.getMetaData(); for (int i = 0; i < metadata.getColumnCount(); i++) { System.out.print("\t"+ metadata.getColumnLabel(i + 1)); } System.out.println("\n----------------------------------"); while (rs.next()) { for (int i = 0; i < metadata.getColumnCount(); i++) { Object value = rs.getObject(i + 1); if (value == null) { System.out.print("\t "); } else { System.out.print("\t"+value.toString().trim()); } } System.out.println(""); } }
}
File: Main.java import javax.persistence.EntityManager; import javax.persistence.EntityManagerFactory; import javax.persistence.Persistence; public class Main {
public static void main(String[] a) throws Exception { JPAUtil util = new JPAUtil(); EntityManagerFactory emf = Persistence.createEntityManagerFactory("ProfessorService"); EntityManager em = emf.createEntityManager(); ProfessorService service = new ProfessorService(em); em.getTransaction().begin(); service.createProfessor("country", 1, "name", 100); Professor emp = service.findProfessor("country", 1); System.out.println("Found " + emp); System.out.println("Professors:"); for (Professor emp1 : service.findAllProfessors()) { System.out.println(emp1); } util.checkData("select * from Professor"); em.getTransaction().rumit(); em.close(); emf.close(); }
}
File: persistence.xml <persistence xmlns="http://java.sun.ru/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.ru/xml/ns/persistence http://java.sun.ru/xml/ns/persistence/persistence" version="1.0"> <persistence-unit name="JPAService" 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:data/tutorial"/> </properties> </persistence-unit>
</persistence>
</source>