File: ParkingSpace.java
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.Table;
@Entity
@Table(name="PARKING_SPACE")
public class ParkingSpace {
@Id
private int id;
private int lot;
private String location;
@OneToOne(mappedBy="parkingSpace")
private Professor employee;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public int getLot() {
return lot;
}
public void setLot(int lot) {
this.lot = lot;
}
public String getLocation() {
return location;
}
public void setLocation(String deptName) {
this.location = deptName;
}
public Professor getProfessor() {
return employee;
}
public void setProfessor(Professor employee) {
this.employee = employee;
}
public String toString() {
return "ParkingSpace id: " + getId() + " lot: " + getLot() +
", location: " + getLocation();
}
}
File: Professor.java
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToOne;
@Entity
public class Professor {
@Id
private int id;
private String name;
@OneToOne
@JoinColumn(name="PSPACE_ID")
private ParkingSpace parkingSpace;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public ParkingSpace getParkingSpace() {
return parkingSpace;
}
public void setParkingSpace(ParkingSpace parkingSpace) {
this.parkingSpace = parkingSpace;
}
public String toString() {
return "Professor id: " + getId() + " name: " + getName() +
" with " + getParkingSpace();
}
}
File: ProfessorService.java
import java.util.Collection;
import javax.persistence.EntityManager;
public class ProfessorService {
protected EntityManager em;
public ProfessorService(EntityManager em) {
this.em = em;
}
public void removeParkingSpace(int empId) {
Professor emp = em.find(Professor.class, empId);
emp.setParkingSpace(null);
em.remove(emp.getParkingSpace());
}
public void removeParkingSpaceWithFailure(int empId) {
Professor emp = em.find(Professor.class, empId);
em.remove(emp.getParkingSpace());
}
public Collection findAllProfessors() {
return (Collection) em.createQuery("SELECT e FROM Professor e").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 java.util.Collection;
import java.util.Iterator;
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.removeParkingSpace(1);
service.removeParkingSpaceWithFailure(1);
util.checkData("select * from Professor");
em.getTransaction().commit();
em.close();
emf.close();
}
}
File: persistence.xml
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence" version="1.0">
JPA-RemovingWithRelationships.zip( 5,335 k)