Hibernate Tutorial 11 - Configuring Collections and Adding Keys --Continued

Configuring Collections and Adding Keys---ended@T19

@you need to use the collections that has index which set collection does not fit here;

@jointable(name="USER_ADDRESS")

@jointable(name="USER_ADDRESS", joinColumns=@JoioColumn(name="USERID")

import org.hibernate.annotations.CollectionOd

import org.hibernate.annotations.GenericGenerator

import org.hibernate.annotations.Type

//which is not JPA anotation specification standard and provided by Hibernate itself;

@Generic Generator(name="hilo-gen", stragedy="hilo")

@CollectionId(columns={@Column="ADDRESS_ID"}, generator = "hilo ", type= @Type(type==long))Hibernate

private Collection<Address> ListOfAddress =new ArrayList<Address>();

 

Proxy Objects and Eager and Lazy Fetch Types:

@ElementCollection(fetch=FetchType.EAGER);

By default, It is the lazy Fetch;

The Fetch strategy is due to the performance consideration;

One To One Mapping

Since this tutorial, we will work on entity inside an entiry which is different from a valuetype(Previous ListOfAddress type) in an entity

One to One mapping means one entity contains another entity;

public class UserDetails

{

private int userId;

private String userName;

 

@OneToOne

@JoinColumn(name="Vehicle_ID")

private Vehicle vehicle;

}

One To Many Mapping

A new user_detail_vehicle table will be created for the mapping between user_detail and vehicle to record the mapping information; 

public class UserDetails

{

@OneToMany

@JoinTable(name="USER_VEHICLE "joinCilumns=@JoinColumn(name="USER_ID), linverseJoinColumn=@JoinColumn(name=VEHICLE_ID)""Vehicle_ID"))

private int userId;

private String userName;

private  Collection<Vehicle> vehicle = new ArrayList<Vehicle>();

}

Many To One Mapping

public class Vehicle

{

@Id @GeneratoedValue

private int vehicle_id;

@ManytoOne

Private UserDetails user;

}

mappedBy and Many To Many Mapping:

 

we do not have seperate table for mappiing vehicle to user_details;

two relationship tables will  be created for manttomany relationship;

public class UserDetails

{

@OneToMany(mappedBy="user")

private int userId;

private String userName;

private Collection<Vehicle> vehicle = new ArrayList<Vehicle>(); //for one to many and many to one and one to one, there is only one collection  for vehicle and user_details;

}

 

public class Vehicle

{

@Id @GeneratoedValue

private int vehicle_id;

@ManytoMany

@JoinColumn(name="USER_ID") // done the mapping within the vehicle using user_id which does not need to create another join table(!@JoinTable)

Private UserDetails user;

private Collection<UserDetail> userDetails userList = new ArrayList();

}

 

CascadeTypes and Hibernate Collections

@NotFound(action=NotFoundAction.IGNORE)

Hibernate Collections

Bag semantic- List/ArrayyList

Bag semantic with ID- List/ArrayyList

List semantic- List/ArrayyList

Set semantic- Set

Map semantic- Map

 

Cascade

public class UserDetails

{

@OneToMany(cascade=CascadeType.PERSIST(also could be all or remove))// which will automatically save the realted references entities(sess.save(userdetails;session.save(vehicle2)) will be changed to be as session.persist(user))

private Collection<Vehicle> vehicle = new ArrayList<Vehicle>(); //for one to many and many to one and one to one, there is only one collection for vehicle and private \

 

Implementing Inheritance:

To take the advantage of the java polyphorsm feature, for e..g., the userdetail class composes/embed a vehicle instance variable which has two subclass boat and car. so Hibernate needs to be aware of the inheritence relateship between entity classes;

By default, it is singble table strategy;

@Inheritance(stratigy=InheritanceType.SINGLE_TABLE)

 

@DiscriminatorColumn{ name="VEHICLE_TYPE",discriminatorType=DiscriminatorType.STRING}

@DiscriminatorValue("BIKE")

 

Implementing Inheritance With Table Per Class:

//multi tables will be created for each class

@Inheritance(stratigy=InheritanceType.TABLE_PER_CLASS)