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 6Basics

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


Why JPA?


Java Persistence Features

Simplify the persistence programming Default over configuration (Convention over configuration )

Elimination of deployment descriptor

Provide light-weight persistence modelIn 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


Java Persistence Features

Support rich domain modelling Support inheritance and polymorphism among entities

Provide standardized and efficient ORMOptimized for relational databaseStandardize 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


JPA Architecture

Java Application Java Persistence API

Hibernate EclipseLink Kodo (OpenJPA)

Everyone can use their own favorite persistence technology


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


Simple MappingMapping 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


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


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)


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


@Table – change the default

name of the table

JPA 2.0 in JAVA EE 6 Basics

@SecondaryTables –

associates a secondary table


O/R Mapping Annotations


@Column – changes

attibutes of the column such

as the name, length and

whether allows NULL or

NOT.


@Basic – overrides basic

persistence

fetch.LAZY

fetch.EAGER


@Temporal – provides representation of

date, hour or milliseconds


@Enumerated – maps the enum values as Text( ORDINAL

default)


@Transient – disables the mapping of a given attribute


@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.

JPA 2.0 in JAVA EE 6 Basics DEMO


Concepts of JPA Operations Entity Manger

Persistent context

Persistent unit


Life Cycle of an Entity

JPA 2.0 in JAVA EE 6

Basics

DEMO


End of

Part I

Basics

Part II – Mapping

Thank you for your patience….

[email protected] Lars Lemos

toplars

mailto:[email protected]

JPA 2.0 in JAVA

EE 6Mapping

Mapping in JPA 2.0 in JAVA EE 6Mapping

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


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.


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


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


Uni-directional Mappings @OneToOne : Employee – ParkingSpace


Uni-directional Mappings @ManyToOne : Employee – Department


Bi-directional Mappings @OneToOne : Employee – ParkingSpace

The owner is the side with he foreign key


Bi-directional Mappings @OneToMany: Employee – Department

The owner is always the “Many” side


Bi-directional Mappings @ManyToMany: Employee – Project


Embedded Objects @ManyToMany: Employee – Project

JPA 2.0 in JAVA

EE 6Query

Mapping in JPA 2.0 in JAVA EE 6Query

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


JPQL


Named query Queries tha can be reusable.


Named query


Dynamic Query Build and execute queries dynamically at runtime.


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….

[email protected] Lars Lemos

toplars

mailto:[email protected]

jpa 2.0 in java ee 6 part ii

Software