EJB3: Entity Relationships Example 3

by admin ~ October 21, 2008

Following are the examples from the chapter “Entity Relationships” from the book “Enterprise JavaBeans 3.0″ by Bill Bruke & Richard Monson-Haefel. This example I have tried it out on JBoss AS 5.0.0.CR1. I have used Postgresql as the database. And I have used eclipse WTP as IDE.

Example 3: Lazy Initialization

Shows the effects of lazy initialization when an entity becomes detached from a persistence context.

Client.java

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package com.titan.clients;
 
import com.titan.access.*;
import com.titan.domain.*;
import javax.naming.InitialContext;
import javax.naming.Context;
import javax.naming.NamingException;
import javax.rmi.PortableRemoteObject;
import java.util.List;
 
public class Client {
	public static void main(String[] args) {
		try {
			Context jndiContext = getInitialContext();
			Object ref = jndiContext.lookup("TitanCruises/DataAccessBean/remote");
			DataAccess dao = (DataAccess) ref;
 
			System.out.println("Fetch reservations with loaded relationships");
			System.out.println();
			List list = dao.fetchReservationsWithRelationships();
			for (Object obj : list) {
				Reservation res = (Reservation) obj;
				System.out.println("Reservation for: "
						+ res.getCruise().getName());
				System.out.println("\tNum cabins: " + res.getCabins().size());
				System.out.println("\tNum customers: "
						+ res.getCustomers().size());
			}
			System.out.println("----------");
			System.out.println("Try to access uninitialized relationships");
			System.out.println("----------");
			list = dao.fetchReservations();
			for (Object obj : list) {
				Reservation res = (Reservation) obj;
				System.out.println("Reservation for: "
						+ res.getCruise().getName());
				try {
					System.out.println("\tNum cabins: "
							+ res.getCabins().size());
					System.out.println("\tNum customers: "
							+ res.getCustomers().size());
				} catch (org.hibernate.LazyInitializationException ex) {
					System.out.println(ex.getMessage());
				}
			}
		} catch (javax.naming.NamingException ne) {
			ne.printStackTrace();
		}
	}
 
	public static Context getInitialContext()
			throws javax.naming.NamingException {
		return new javax.naming.InitialContext();
	}
}

jndi.properties

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java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory
java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces
java.naming.provider.url=127.0.0.1:1099

Address.java

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package com.titan.domain;
 
import javax.persistence.*;
 
@Entity
public class Address implements java.io.Serializable {
	private int id;
	private String street;
	private String city;
	private String state;
	private String zip;
 
	@Id
	@GeneratedValue
	public int getId() {return id;}
	public void setId(int id) {this.id = id;}
	public String getStreet() {return street;}
	public void setStreet(String street) {this.street = street;}
	public String getCity() {return city;}
	public void setCity(String city) {this.city = city;}
	public String getState() {return state;}
	public void setState(String state) {this.state = state;}
	public String getZip() {return zip;}
	public void setZip(String zip) {this.zip = zip;}
}

Cabin.java

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package com.titan.domain;
 
import javax.persistence.*;
 
@Entity
public class Cabin implements java.io.Serializable {
	private int id;
	private String name;
	private int bedCount;
	private int deckLevel;
	private Ship ship;
 
	@Id
	@GeneratedValue
	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 int getBedCount() {return bedCount;}
	public void setBedCount(int count) {this.bedCount = count;}
	public int getDeckLevel() {return deckLevel;}
	public void setDeckLevel(int level) {this.deckLevel = level;}
	@ManyToOne
	@JoinColumn(name = "SHIP_ID")
	public Ship getShip() {return ship;}
	public void setShip(Ship ship) {this.ship = ship;}
}

CreditCard.java

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package com.titan.domain;
 
import javax.persistence.*;
import java.util.Date;
 
@Entity
public class CreditCard implements java.io.Serializable {
	private int id;
	private Date expirationDate;
	private String number;
	private String nameOnCard;
	private String creditOrganization;
	private Customer customer;
 
	@Id
	@GeneratedValue
	public int getId() {return id;}
	public void setId(int id) {this.id = id;}
	public Date getExpirationDate() {return expirationDate;}
	public void setExpirationDate(Date date) {expirationDate = date;}
	public String getNumber() {return number;}
	public void setNumber(String number) {this.number = number;}
	public String getNameOnCard() {return nameOnCard;}
	public void setNameOnCard(String name) {nameOnCard = name;}
	public String getCreditOrganization() {return creditOrganization;}
	public void setCreditOrganization(String org) {creditOrganization = org;}
	@OneToOne(mappedBy = "creditCard")
	public Customer getCustomer() {return customer;}
	public void setCustomer(Customer customer) {this.customer = customer;}
}

Cruise.java

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package com.titan.domain;
 
import java.util.*;
import javax.persistence.*;
 
@Entity
public class Cruise implements java.io.Serializable {
	private int id;
	private String name;
	private Ship ship;
 
	private Collection<Reservation> reservations = new ArrayList<Reservation>();
 
	public Cruise() {}
	public Cruise(String name, Ship ship) {
		this.name = name;
		this.ship = ship;
	}
 
	@Id
	@GeneratedValue
	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;}
	@ManyToOne
	public Ship getShip() {return ship;}
	public void setShip(Ship ship) {this.ship = ship;}
	@OneToMany(mappedBy = "cruise")
	public Collection<Reservation> getReservations() {return reservations;}
	public void setReservations(Collection<Reservation> res) {reservations = res;}
}

Customer.java

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package com.titan.domain;
 
import javax.persistence.*;
import java.util.*;
 
@Entity
public class Customer implements java.io.Serializable {
	private int id;
	private String firstName;
	private String lastName;
	private boolean hasGoodCredit;
	private Address address;
	private Collection<Phone> phoneNumbers = new ArrayList<Phone>();
	private CreditCard creditCard;
	private Collection<Reservation> reservations = new ArrayList<Reservation>();
 
	@Id
	@GeneratedValue
	public int getId() {return id;}
	public void setId(int id) {this.id = id;}
	public String getFirstName() {return firstName;}
	public void setFirstName(String firstName) {this.firstName = firstName;}
	public String getLastName() {return lastName;}
	public void setLastName(String lastName) {this.lastName = lastName;}
	public boolean getHasGoodCredit() {return hasGoodCredit;}
	public void setHasGoodCredit(boolean flag) {hasGoodCredit = flag;}
 
	@OneToOne(cascade = { CascadeType.ALL })
	@JoinColumn(name = "ADDRESS_ID")
	public Address getAddress() {return address;}
	public void setAddress(Address address) {this.address = address;}
 
	@OneToOne(cascade = { CascadeType.ALL })
	public CreditCard getCreditCard() {return creditCard;}
	public void setCreditCard(CreditCard card) {creditCard = card;}
 
	@OneToMany(cascade = { CascadeType.ALL })
	@JoinColumn(name = "CUSTOMER_ID")
	public Collection<Phone> getPhoneNumbers() {return phoneNumbers;}
	public void setPhoneNumbers(Collection<Phone> phones) {this.phoneNumbers = phones;}
 
	@ManyToMany(mappedBy = "customers")
	public Collection<Reservation> getReservations() {return reservations;}
	public void setReservations(Collection<Reservation> reservations) {this.reservations = reservations;}
}

Phone.java

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package com.titan.domain;
 
import javax.persistence.*;
 
@Entity
public class Phone implements java.io.Serializable {
	private int id;
	private String number;
	private byte type;
 
	@Id
	@GeneratedValue
	public int getId() {return id;}
	public void setId(int id) {this.id = id;}
	public String getNumber() {return number;}
	public void setNumber(String number) {this.number = number;}
	public byte getType() {return type;}
	public void setType(byte type) {this.type = type;}
}

Reservation.java

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package com.titan.domain;
 
import javax.persistence.*;
import java.util.*;
 
@Entity
public class Reservation implements java.io.Serializable {
	private int id;
	private Date date;
	private double amountPaid;
	private Cruise cruise;
	private Set<Cabin> cabins = new HashSet<Cabin>();
	private Set<Customer> customers = new HashSet<Customer>();
 
	@Id
	@GeneratedValue
	public int getId() {return id;}
	public void setId(int id) {this.id = id;}
	public Date getDate() {return date;}
	public void setDate(Date date) {this.date = date;}
	public double getAmountPaid() {return amountPaid;}
	public void setAmountPaid(double amount) {amountPaid = amount;}
 
	@ManyToOne
	@JoinColumn(name = "CRUISE_ID")
	public Cruise getCruise() {return cruise;}
	public void setCruise(Cruise cruise) {this.cruise = cruise;}
 
	@ManyToMany
	@JoinTable(name = "RESERVATION_CABIN", joinColumns = { @JoinColumn(name = "RESERVATION_ID") }, inverseJoinColumns = { @JoinColumn(name = "CABIN_ID") })
	public Set<Cabin> getCabins() {return cabins;}
	public void setCabins(Set<Cabin> cabins) {this.cabins = cabins;}
 
	@ManyToMany
	@JoinTable(name = "RESERVATION_CUSTOMER", joinColumns = { @JoinColumn(name = "RESERVATION_ID") }, inverseJoinColumns = { @JoinColumn(name = "CUSTOMER_ID") })
	public Set<Customer> getCustomers() {return customers;}
	public void setCustomers(Set<Customer> customers) {this.customers = customers;}
}

Ship.java

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package com.titan.domain;
 
import javax.persistence.*;
 
@Entity
public class Ship implements java.io.Serializable {
	private int id;
	private String name;
	private double tonnage;
 
	public Ship() {}
	public Ship(String name, double tonnage) {
		this.name = name;
		this.tonnage = tonnage;
	}
 
	@Id
	@GeneratedValue
	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 double getTonnage() {return tonnage;}
	public void setTonnage(double tonnage) {this.tonnage = tonnage;}
}

Initializedb.java

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package com.titan.clients;
 
import com.titan.access.*;
import com.titan.domain.*;
import javax.naming.InitialContext;
import javax.naming.Context;
import javax.naming.NamingException;
import javax.rmi.PortableRemoteObject;
import java.util.List;
 
public class Initializedb {
	public static void main(String[] args) {
		try {
			Context jndiContext = getInitialContext();
			Object ref = jndiContext.lookup("TitanCruises/DataAccessBean/remote");
			DataAccess dao = (DataAccess) ref;
			System.out.println(dao.initializeDatabase());
		} catch (javax.naming.NamingException ne) {
			ne.printStackTrace();
		}
	}
 
	public static Context getInitialContext()
			throws javax.naming.NamingException {
		return new javax.naming.InitialContext();
	}
}

DataAccess.java

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package com.titan.access;
 
import javax.ejb.Remote;
import java.util.List;
 
@Remote
public interface DataAccess {
   String initializeDatabase();
   public List fetchReservations();
   public List fetchReservationsWithRelationships();
}

DataAccessBean.java

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package com.titan.access;
 
import javax.persistence.*;
import javax.ejb.*;
import java.io.*;
import com.titan.domain.*;
import java.util.List;
import java.util.Date;
 
@Stateless
public class DataAccessBean implements DataAccess {
	@PersistenceContext(unitName = "titan")
	EntityManager manager;
 
	public List fetchReservations() {
		return manager.createQuery("FROM Reservation res").getResultList();
	}
 
	public List fetchReservationsWithRelationships() {
		List list = manager.createQuery("FROM Reservation res").getResultList();
		for (Object obj : list) {
			Reservation res = (Reservation) obj;
			res.getCabins().size();
			res.getCustomers().size();
		}
		return list;
	}
 
	public String initializeDatabase() {
		List list = manager.createQuery("FROM Reservation res").getResultList();
		if (list.size() > 0) {
			return "Database already initialized with entities";
		}
 
		String output = null;
		StringWriter writer = new StringWriter();
		PrintWriter out = new PrintWriter(writer);
 
		Customer bill = new Customer();
		bill.setFirstName("Bill");
		bill.setLastName("Burke");
		bill.setHasGoodCredit(true);
 
		Customer sacha = new Customer();
		sacha.setFirstName("Sacha");
		sacha.setLastName("Labourey");
		sacha.setHasGoodCredit(false); // Sacha get's bad credit ;)
 
		Customer marc = new Customer();
		marc.setFirstName("Marc");
		marc.setLastName("Fleury");
		marc.setHasGoodCredit(true);
 
		Address addr = new Address();
		addr.setStreet("123 Boston Road");
		addr.setCity("Billerica");
		addr.setState("MA");
		addr.setZip("01821");
		bill.setAddress(addr);
 
		addr = new Address();
		addr.setStreet("Etwa Schweitzer Strasse");
		addr.setCity("Neuchatel");
		addr.setState("Switzerland");
		addr.setZip("07711");
		sacha.setAddress(addr);
 
		addr = new Address();
		addr.setStreet("JBoss Dr.");
		addr.setState("Atlanta");
		addr.setCity("GA");
		addr.setZip("06660");
		marc.setAddress(addr);
 
		CreditCard cc;
		cc = new CreditCard();
		cc.setExpirationDate(new Date());
		cc.setNumber("5324 9393 1010 2929");
		cc.setNameOnCard("Bill Burke");
		cc.setCreditOrganization("Capital One");
		bill.setCreditCard(cc);
 
		cc = new CreditCard();
		cc.setExpirationDate(new Date());
		cc.setNumber("3311 5000 1011 2333");
		cc.setNameOnCard("Sacha Labourey");
		cc.setCreditOrganization("American Express");
		sacha.setCreditCard(cc);
 
		cc = new CreditCard();
		cc.