Enterprise Java Development@TOPIC@

Chapter 46. Identifying Entity Classes

46.1. Entities
46.2. Entity Name
46.3. Field/Property Access
46.3.1. Access Types
46.3.2. Defining Access using @Annotations
46.3.3. Defining Access using orm.xml
46.4. Approaches
46.4.1. Java First
46.4.2. Schema First

46.1. Entities

Figure 46.1. Annotated Class Example

package ejava.examples.orm.core.annotated;


import javax.persistence.*; //brings in JPA Annotations


(1)@Entity 

public class Bike {

(2)    @Id   //tells ORM that this property provides pk simple value

    private long id;

    private String make;

    private String model;

    private int size;

    

(3)    public Bike() {} //required non-private default ctor

    public Bike(long id) { this.id = id; }


    public long getId() {

        return id;

    }


    public String getMake() { return make; }

    public void setMake(String make) {

        this.make = make;

    }

...

}
1

Tells provider to include in persistence unit

2

Tells provider to use this property as the primary key

3

Default ctor required for provider to instantiate from DB


Figure 46.2. Mapped Class Example

package ejava.examples.orm.core.mapped;


public class Bike {

(1)    private long id; //orm.xml file will map this field to Identity

    private String make;

    private String model;

    private int size;

    

(2)    public Bike() {}

    public Bike(long id) { this.id = id; }


    public long getId() {

        return id;

    }


    public String getMake() { return make; }

    public void setMake(String make) {

        this.make = make;

    }

...

}
1

Must have a property to later define as a primary key

2

Must have a default ctor


Figure 46.3. Mapped Class ORM.xml Example

<?xml version="1.0" encoding="UTF-8"?>

<entity-mappings xmlns="http://java.sun.com/xml/ns/persistence/orm"

 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

 xsi:schemaLocation="http://java.sun.com/xml/ns/persistence/orm 

                     http://java.sun.com/xml/ns/persistence/orm_2_0.xsd"

 version="2.0">

            

(1)    <entity class="ejava.examples.orm.core.mapped.Bike" 

            access="FIELD"

            metadata-complete="true"

            name="MappedBike">

        <table name="Bike"/>

        <attributes>

(2)            <id name="id"/>

        </attributes>

    </entity>    

</entity-mappings>
1

Identifies class as an entity

2

Identifies @Id property for a primary key


Figure 46.4. Mapped Class META-INF/persistence.xml Reference

<?xml version="1.0" encoding="UTF-8"?>

<persistence xmlns="http://java.sun.com/xml/ns/persistence"

 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

 xsi:schemaLocation="http://java.sun.com/xml/ns/persistence 

  http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"

 version="2.0">


(1)    <persistence-unit name="ormCore">

(2)        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>

        <mapping-file>orm/Bike-orm.xml</mapping-file>

        <class>ejava.examples.orm.core.annotated.Bike</class>

...

    </persistence-unit>        

    

</persistence>
1

Reference to orm.xml to map Java class(es) to database and make part of persistence unit

2

Reference to class that may/may not be within local archive but should be part of persistence unit


Figure 46.5. Example Directory Structure

src/
|-- main
|   |-- java
|   |   `-- ejava
...
|   |                   |-- annotated
|   |         (1)          |   `-- Bike.java
|   |                   `-- mapped
|   |         (2)              `-- Bike.java
|   `-- resources
|       |-- META-INF
|       |   `-(3)- persistence.xml
|       `-- or(4)m
|           `-- Bike-orm.xml
`-- test
    `-- resour(5)ces
        `-- hibernate.properties
1

Annotated class

2

Pure-POJO class mapped by orm.xml

3

persistence.xml defines reference to orm.xml

4

orm.xml defines Java class mapping to database

5

Properties file with database runtime properties


46.2. Entity Name

46.3. Field/Property Access

FIELD Access

Direct access to Java variable

PROPERTY Access

Accessed through Java set/get methods

46.4. Approaches