1 4 Annotating Persistence

8/6/2019 1 4 Annotating Persistence

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Annotating Persistence

Applications

Struts University Series




ApplicationsIn this session, we learn how to use

annotations to describe object

relationships and associations that theJPA cannot deduce on its own.

In the lab, we extend the User object to

include other properties, including a listof subscriptions.




ApplicationsWhat are annotations?

How do we declare properties?

How do we declare relationships?

How do we declare inheritance?



What are annotations?

Advanced mechanisms often need

different concerns to work together

Dynamic proxy may need a paired interfaceand implementation (Web Services)

JavaBeans may need a way to override

getter/setter conventions (BeanInfo)

Serialization may not need to serialize

everything (transient)

We may need to indicate that a member is

being retired (@deprecated)




Message Resources (*_es.properties)

Deployment descriptors (web.xml)

Workflow configuration (struts.xml)

Object validation (object-validator.xml)




Annotations are a Java 5 mechanism for

attaching metadata (gluecode) to a

member @Annotation(name=value) member

Available to Java as XDoclet for years

Available in C# for even longer JPA is annotation-enabled XML descriptor can override annotations



What are the JPA Annotations?

Entity

Locking

Identity

Composition

Database Schema

Attributes

Direct Mappings

Relationship

Mappings

Queries

Entity Manager

Inheritance

Lifecycle CallBack

Events

http://www.oracle.com/technology/products/ias/toplink/jpa/resources/toplink-jpa-annotations.html





Entity / Locking

@Entity @Version



Identity

@Id

@IdClass

@EmbeddedId@GeneratedValue

@SequenceGenerator

@TableGenerator



Database Schema Attributes

@Table

@SecondaryTable

@SecondaryTables@Column

@JoinColumn

@JoinColumns

@PrimaryKeyJoinColumn

@PrimaryKeyJoinColumns

@JoinTable

@UniqueConstraint



Direct Mappings

@Basic

@Enumerated

@Temporal@Lob

@Transient



Relationship Mappings

@OneToOne

@OneToMany

@ManyToOne@ManyToMany

@MapKey

@OrderBy



Queries

@NamedQuery

@NamedQueries

@NamedNativeQuery@NamedNativeQueries

@QueryHint

@ColumnResult

@EntityResult

@FieldResult

@SqlResultSetMapping

@SqlResultSetMappings



Composition

@Embeddable

@Embedded

@AttributeOverride@AttributeOverrides

@AssociationOverride

@AssociationOverrides



Inheritance

@Inheritance

@DiscriminatorColumn

@DiscriminatorValue@MappedSuperclass

@AssociationOverride

@AssociationOverrides

@AttributeOverride

@AttributeOverrides



Lifecycle Callback Events

@PrePersist

@PostPersist

@PreRemove@PostRemove

@PreUpdate

@PostUpdate

@PostLoad

@EntityListeners@ExcludeDefaultListeners

@ExcludeSuperclassListeners



Entity Manager

@PersistenceUnit

@PersistenceUnits

@PersistenceContext@PersistenceContexts

@PersistenceProperty













Entity

Table

Column

Id

GeneratedValue

Version

Basic

Transient



Entity

@Entity public class User implements Serializable {

@Entity is requiredMust be persisted by EntityManager

Serializable is recommended



Entity

@Entity(name=”USER”) public class UserImpl extends UuidEntity

implements User, Serializable {

Name attribute is used by queries (SELECT u FROM USER)Defaults to class name



Entity

@Entity public class User implements Serializable { @Id // field access private String id ; public String getId() { return id ; } public void setId(String value) { id = value; }}

Primary key (@Id) is required



Entity

@Entity public class User implements Serializable { private String id ; @Id // property access public String getId() { return id ; } public void setId(String value) { id = value; }}

Either fields or getters may be annotated But not both in the same class hierarchy!



Table

@Entity(name="USER")@Table(name="APP_USER")

public class UserImpl extends UuidEntity implements Serializable, User {

name, catalog, schema, uniqueConstantsWorks well with Entity to isolate per database settings



Column

name, unique, nullable, insertable, updatable,columnDefinition, table, length, precision, scale

// ... public class User implements Serializable { @Column(length = 64) private String from_address;public String getFromAddress()

{return from_address;} // ...}



Id

public class Message { @Id private Long id ;}

Use @Column to specify a different namePrimitive or wrapper type, String, Date (sql or util)



GeneratedValue

public class Message { @Id @GeneratedValue private Long id ;

// ...}

public class Message { @Id @GeneratedValue(GenerationType.SEQUENCE) private Long id ;

// ...

}

Used with @Id

.AUTO, IDENTITY, .SEQUENCE



Version

public class UuidEntity implements Serializable {

@Version private Timestamp last_update;

// ...}

int, Integer, short, Short, long, Long,Timestamp



Basic

Default annotation for unannotated fields or propertiesfetch, optional

FetchType = (EAGER, LAZY)

// ...@Basic(fetch=FetchType.LAZY )

private List<Subscription> subscriptions;// ...



Basic

Java primitive types, wrappers of the primitive types,String, BigInteger, BigDecimal, util.Date,

Calendar, sql.Date, Time, Timestamp, byte[],

Byte[], char[], Character[], enums, and any

other type that implements Serializable.

// ...@Basic(fetch=FetchType.LAZY )

private List<Subscription> subscriptions;// ...



Transient

@Entity public class User { @Transient private String password1 = null;// ...}

@Entity public class User implements Serializable {

private transient String password1 = null;// ...}

Transient members are not persisted













@OneToOne

@OneToMany

@ManyToOne

@NamedQuery

@NamedQueries



OneToOne

cascade, fetch, mappedBy, optional, targetEntity,

@Entity@Table(name = "APP_MESSAGE")

public class Message implements Serializable { @Id @GeneratedValue

private Long id; @OneToOne(cascade = CascadeType.ALL) private Message message;

// ...

}



OneToMany

cascade, fetch, mappedBy, targetEntity

// ... public class User implements Serializable {

@OneToMany(cascade = CascadeType.ALL)

private List<Subscription> subscriptions;

// ... public class UserImpl extends UuidEntity implements

@OneToMany(cascade = CascadeType.ALL, mappedBy=”user”, targetEntity=SubscriptionImpl.class) private List<Subscription> subscriptions;



OneToMany


public class UserImpl extends UuidEntity implements


Inverse side of the relationship





What's an “owner” or “inverse”

side of a relationship?Owner “persists” the relationship To change which instances are related,

which side (table) do we change? Terminology may seem counter-intuitive



What's an “owner” or “inverse”

side of a relationship?In 1:M or M:1, Many is always the owner. Change the key on the many side, change

the relationship, (Can't change the One, because the the One

side is usually a primary key!)

Important because application must keep

relationships synchronized with anychanges



OneToMany




Inverse side of the relationship



ManyToOne

// ... public class SubscriptionImpl extends UuidEntity

@JoinColumn(nullable = false) @ManyToOne(targetEntity = UserImpl.class) private User user;

Owner side of the relationship



NamedQuery

Name, query, queryHint[]

@Entity@NamedQuery(name = "User.COUNT",

query = "SELECT COUNT(*) FROM USER") public class User implements Serializable {



NamedQuery

Hints are provider-specific options or settings

cacheable, timeout, readOnly, comment

@Entity@NamedQuery(

name="findAllEmployees",query="SELECT * FROM EMPLOYEE WHERE MGR=1"

hints={@QueryHint(name=TopLinkQueryHints.REFRESH, value=HintValues.TRUE)

})



NamedQueries

@NamedQueries( {@NamedQuery(name = User.FIND_ALL,

query = UserImpl.FIND_ALL_QUERY ),@NamedQuery(name = User.FIND_BY_NAME ,

query = UserImpl.FIND_BY_NAME_QUERY ),@NamedQuery(name = User.COUNT ,

query = UserImpl.COUNT_QUERY )})
























Resources

Toplink JPA Annotation Reference http://www.oracle.com/technology/products/ias/toplink/jpa/resources/toplink-jpa-annotations.html

/docs/jpa-docs/toplink-jpa-annotations.pdf

JPA Specification, Chapters 8 and 9 http://jcp.org/en/jsr/detail?id=220

/docs/jpa-docs/ejb3_0-fr-spec-persistence.pdf

The Java Persistence APIA Simpler Programming Model for Entity Persistence

http://java.sun.com/developer/technicalArticles/J2EE/jpa/

/docs/jpa-docs/j2ee-jpa.pdf


http://jcp.org/en/jsr/detail?id=220



http://jcp.org/en/jsr/detail?id=220




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1 4 Annotating Persistence