Jpa 2.0 in java ee 6 part ii

JPA 2.0
in JAVA
EE 6
Basics
Mapping
Query
Transaction and Concurrency

JPA 2.0 in JAVA EE 6
Basics
What is JPA?
 Java EE Standard ORM Framework JPA 2.0 (JSR 317)
 JPA 1.0 part of EJB 3.0 JSR 220
 JPA 2.0 standalone JSR 317
 JPA 2.1 (JSR 338) included in Java EE 7
 Enables transparent POJO Persistence
 Handles Object Relational impedance mismatch
 Enables building persistent objects following common
OOP concepts

Basics
Why JPA?

Basics
Java Persistence Features
 Simplify the persistence programming
 Default over configuration (Convention over configuration )
 Elimination of deployment descriptor
 Provide light-weight persistence model
 In both programming model and deployment
 Runtime performance
 Enable testability outside of the containers
 Enables test-driven development
 Test entities as part of nightly-buid process

Basics
Java Persistence Features
 Support rich domain modelling
 Support inheritance and polymorphism among entities
 Provide standardized and efficient ORM
 Optimized for relational database
 Standardize annotations and XML configuration files
 Provide extensive querying capabiliies
 Support for pluggable, third-party persistence providers.
 Through persistence unit – represented by persistence.xml
 Persistence API expanded to include use outside EJB
container
 Evolved into “common” Java persistence API between Java
SE and Java EE apps

Basics
JPA Architecture
Java Application Java Persistence API
Hibernate EclipseLink Kodo (OpenJPA)
Everyone can use their own favorite persistence technology

Basics
Entity
 Plain Old Java Object (POJO)
 Supports OO programming model, (PIE)
 Can be in either persistent(manage) or non-persistent
state (detached)
 Example of non-persistent state is “transient” state
 Have persistent identity
 When it is in managed state
 Can extend other entity and non-entity classes
(Inheritance)
 Serializable; usable as detached objecs in other tiers

Basics
Simple Mapping
Mapping defaults to
matching column name.
Default Mapping
 Entity name -> table name
(customizable via @Table)
 Attribute name -> column
name(customizable via
@Column)
 Data type mapping (some
differences among databases)
 String -> VARCHAR(255)
 Long, long -> BIGINT
 Double, double -> DOUBLE
 Boolean -> SMALLINT

Basics
Entity Class (@Entity)
 Annotated with @Entity
 Can extend another entity
 Can be a concrete or abstract class
 Programming requirement
 Must have a primary key field
 Must have a public no-arg constructor
 Instance variables must not be public
 Must not be final or have final methods

Basics
Entity Identity (@Id, @GeneratedValue )
 Every entity has a persistence identity
 Maps to primary key in database
 Cancorrespond to simple type
 @Id – single field/property in entity class
 @GeneratedValue – value can be generated automatically using
various strategies
 AUTO – Choose type depending on database, e.g: IDENTITY for
MySQL
 IDENTITY – using a database identity column
 SEQUENCE – using a database sequence
 TABLE – Use a sequence table for key generation (most portable)

Basics
O/R Mapping Annotations
 Set of annotations defined for mapping
(Relationships, Joins, Database tables and
columns)
 An Example Data Model
 Maps entity state to data store
 Maps relationships to other entities

Basics
@Table – change the default
name of the table

JPA 2.0 in JAVA EE 6 Basics
@SecondaryTables –
associates a secondary table

BasicsO/R Mapping Annotations

Basics
@Column – changes
attibutes of the column such
as the name, length and
whether allows NULL or NOT.

Basics
@Basic – overrides basic
persistence
 fetch.LAZY
 fetch.EAGER

Basics
@Temporal – provides representation of
date, hour or milliseconds

Basics
@Enumerated – maps the enum values as Text( ORDINAL
default)

Basics
@Transient – disables the mapping of a given attribute

Basics
@CollectionTable – specifies the table
that is used for the mapping of collection
of basic or embeddable types.
@ElementCollection – inform the
persistence provider rerence is a set of
collection and defines the “fetch”
mode.

Basics DEMO

Basics
Concepts of JPA Operations
 Entity Manger
 Persistent context
 Persistent unit

Basics
Life Cycle of an Entity

Basics
DEMO

End of
Part I
Basics
Part II – Mapping
Thank you for your patience….
larslemos@gmail.com
Lars Lemos
toplars

Mapping in JPA 2.0 in JAVA EE 6
Mapping
Types of Entity Relationship
 Directionality
 Uni-directional
 Bi-directional
 Cardinality relationships
 One to one
 One to many
 Many to many
 Inheritance relationship
 Single table
 Joined Table

Mapping
Directionality & Ownership
 Relationship has an ownership
 Who owns the relationship affects how tables are created.
 Uni-directional
 Ownership is implied
 Bi-directional
 Ownership needs to be explicitly specified.
 Owner of the relationship, inverse-owner of the relationship.

Mapping
Directionality & Navigation
 Directionality affects the navigation
 Uni-directional
 customer.getAddress() is allowed but address.getCustomer() is not supported
for 1-1 relationship
 customer.getOrders() is allowed but order.getCustomers() is not supported for
1-m relationship.
 speaker.getEvents() is allowed but event.getSpeakers() is not supported for n-
m relationship.
 Bi-directional
 Navigation on both direction

Mapping
Cardinality Relationship
 Cardinality relationships
 @OneToOne : Customer – Address
 @OneToMany: Customer – Orders
 @ManyToMany : Speakers – Events
 @ManyToOne: Employee - Project
 One-to-Many and Many-to-Many relationships are
represented in Java code through
 Collection, Set, List and Map

Mapping
Uni-directional Mappings
 @OneToOne : Employee – ParkingSpace

Mapping
Uni-directional Mappings
 @ManyToOne : Employee – Department

Mapping
Bi-directional Mappings
 @OneToOne : Employee – ParkingSpace
 The owner is the side with he foreign key

Mapping
 @OneToMany: Employee – Department
 The owner is always the “Many” side

Mapping
 @ManyToMany: Employee – Project

Mapping
Embedded Objects
 @ManyToMany: Employee – Project

Query
JPA Query Features
 Static queries
 Defined with Java language metadata or XML
 Anonotations: @NamedQuery, @NamedNativeQuery
 Dynamic queries
 Query string can be created at runtime.
 Use Java Persistence Query Language (JPQL) or SQL
 Named or positional parameters
 EntityManager is factory for Query objects
 createNamedQuery, createQuery, createNativeQuery
 Query methods for controlling max results, pagination, flush
mode

Query
 JPQL

Query
 Named query
 Queries tha can be reusable.

Query
 Named query

Query
 Dynamic Query
 Build and execute queries dynamically at runtime.

Query
 Native Query
 Build and execute queries based on native SQL.

Mapping &
Querying
DEMO

End of
Part III
Basics
Part IV – Advanced JPA & Transactions
Thank you for your patience….
larslemos@gmail.com
Lars Lemos
toplars

Jpa 2.0 in java ee 6 part ii

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