1. Object/Relational Mapping Solving the structural paradigm mismatch

5. A simple POJO public class User implements Serializable { private String username; private Address address; public User() {} public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public Address getAddress() { return address;} public void setAddress(Address address) { this.address = address; } public MonetaryAmount calcShippingCosts(Address from) { ... } }

27. The tables of this association mapping << table >> ITEM ITEM_ID <<PK>> NAME PRICE ... << table >> BID BID_ID <<PK>> ITEM_ID <<FK>> AMOUNT ... PRICE NAME ITEM_ID 1 2 3 Bar Foo Baz 2.00 50.00 1.00 ITEM AMOUNT ITEM_ID BID_ID 1 2 3 1 1 2 10.00 20.00 55.00 BID

32. Mapping collections vs Java collections Persists an unordered,non-unique many-to-many collection using a surrogate key. java.util.List idbag Persists an indexed, non-unique collection of primitive values N/A primitive-array Persists an indexed, non-unique collection of values or objects N/A array Persists an unordered, non-unique collection of values or objects java.util.List bag Persists an ordered,non-unique collection of values or objects java.util.List list Persists a collection of key/value pairs java.util.Map map Persists an unordered,unique collection of values or objects java.util.Set set Description Java Collection Type Hibernate Collection Type

33. One-to-many association <hibernate-mapping package=“demo”> <class name=“Event” table=“events”> … . <set name=“speakers”> <key column=“event_id”/> <one-to-many class=“Speaker”/> </set> <set name=“attendees”> <key column=“event_id”/> <one-to-many class=“Attendee”/> </set> … . </class> </hibernate-mapping> public class Event { private Set speakers; private set attendees; public void setSpeakers(Set speakers) { this.speakers=speakers;} public set getSpeakers() {return this.speakers;} public void setAttendees(Set attendees) { this.attendees=attendees;} public set getAttendees() {return this.attendees;}

34. One-to-many events events events attendees id bigint(pk) id bigint (pk) event_id bigint (fk) A one-to-many association from events to attendees

36. many-to-many events events events event_attendees id bigint(pk) event_id bigint (fk) attendee_id bigint (fk) A many-to-many table schema from events to attendees events events attendees id bigint(pk)

42. idbags events events events event_attendees id bigint(pk) event_id bigint speaker_id bigint events events speakers id bigint(pk) event_speaker_id bigint (PK)

52. Adding a property at runtime // Get the existing mapping for User from Configuration PersistentClass userMapping = cfg .getClassMapping(User.class); // Define a new column for the USER table Column column = new Column(); userMapping.getTable().addColumn(column); // Wrap the column in a Value SimpleValue value = new SimpleValue(); value.setTable( userMapping.getTable() ); value.addColumn(column); // Define a new property of the User class Property prop = new Property(); prop.setValue(value); prop.setName(&quot;motto&quot;); userMapping.addProperty(prop); // Build a new session factory, using the new mapping SessionFactory sf = cfg.buildSessionFactory();