com.hp.util.dao

Class AbstractBidirectionalDependentDao<I extends Serializable,P extends Storable<I> & Dependable<E>,T extends Transportable<? super T,I> & Dependent<R>,Q extends Transportable<? super Q,I> & Dependent<E>,F,S,E extends Serializable,W extends Storable<E>,R extends Transportable<? super R,E>>

java.lang.Object

com.hp.util.dao.AbstractBaseDao<I,P,T,F,S>

com.hp.util.dao.AbstractBidirectionalDependentDao<I,P,T,Q,F,S,E,W,R>

Type Parameters:

I - type of the persistent object and transport object id. This type should be immutable. It is critical this type implements equals() and hashCode() correctly.

P - type of the persistent object.

T - type of the transport object with a reference to the owner.

Q - type of the transport object with a reference to the owner's id.

F - type of the associated filter.

S - type of the associated sort specification type.

E - type of the owner persistent object and owner transport object id. This type should be immutable. It is critical this type implements equals() and hashCode() correctly.

W - type of the owner persistent object.

R - type of the owner transport object.

All Implemented Interfaces:

Converter<P,Q>, BaseDao<I,P,T,F,S>, BidirectionalDependentDao<I,P,T,Q,F,S,E,W,R>

public abstract class AbstractBidirectionalDependentDao<I extends Serializable,P extends Storable<I> & Dependable<E>,T extends Transportable<? super T,I> & Dependent<R>,Q extends Transportable<? super Q,I> & Dependent<E>,F,S,E extends Serializable,W extends Storable<E>,R extends Transportable<? super R,E>>
extends AbstractBaseDao<I,P,T,F,S>
implements BidirectionalDependentDao<I,P,T,Q,F,S,E,W,R>

JPA Data Access Object for a storable that is the dependent object in a one-to-many bidirectional relation.

One to Many Relations with Dependent Entities

Note that any other type of relation (One to many or many to many with independent entities) could be implemented using Daos.

• Let Item be a model object.
• Let Image be a model object.
• One item may have several images (One-to-Many relation). So Item has a collection of Image. Dependent classes are modeled as value type (Collection of value type).
• Let ItemEntity be a storable.
• Let ItemImageEntity be the dependent storable. The dependent object has no life outside of the collection; it's dependent on an Item entity.
• A regular Dao may be used to access ItemEntity.
• If the association from Item to Image is unidirectional then the same regular Dao that access ItemEntity could also access ItemImageEntity. No need of a separated DAO for ItemImageEntity since JPA will propagate updates when the collection of dependent entities is modified. The Dao will just need to create an ItemImageEntity from Image and vice-verza. With an unidirectional relation you can navigate to the images by accessing the collection through an item instance. This is the only way you can get the images objects; no other entity holds a reference to them (dependent entity value type).
• If the association from Item to Image is bidirectional a BidirectionalDependentDao should be used to access ItemImageEntity. In a bidirectional relation it is possible to navigate from an Image back to an Item. Note this type of navigation does not make much sense and should be avoided if possible. The JPA provider (Like Hibernate) can fill in this property for you if you annotate your entity accordingly. True bidirectional navigation is impossible with JPA, however. You can't retrieve an ItemImageEntity independently and then navigate back to its parent ItemEntity. This is an important issue: You can load ImageEntity instances by querying for them. But these images won't have a reference to their owner (the property is null). For this reason this implementation introduces Dependable to keep a reference of the owner's id so it can be manually retrieved (Since JPA provider won't fill the owner if the dependent object is queried by itself).

Annotations Examples:

One to many association in the independent object

  @OneToMany(cascade=CascadeType.ALL, mappedBy="owner", orphanRemoval=true)
  private Collection<ItemImageEntity> images = new ArrayList<ItemImageEntity>();
 

One to many association in the dependent object

 @ManyToOne
 @JoinColumn(name = "owner_fk")
 private ItemEntity owner;
 
 // Needed to implement true bidirectional navigation. See Dependable note above.
 @Column(name = "owner_id")
 private Long ownerId;
 

Author:

Fabiel Zuniga, Scott Simes

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractBidirectionalDependentDao(Class<P> entityClass) Construct DAO and initialize query predicate generator.
protected	AbstractBidirectionalDependentDao(Class<P> entityClass, UpdateStrategy<P,T> updateStrategyT, UpdateStrategy<P,Q> updateStrategyQ) Construct DAO and initialize query predicate generator.

Method Summary

Methods

Modifier and Type	Method and Description
protected abstract void	conformQ(P target, Q source) Synchronizes the transport object and the persistent object state.
protected abstract void	conformT(P target, T source) Synchronizes the transport object and the persistent object state.
Q	convert(P source) Converts an instance of type S to an instance of type T
T	convert(P storable, BaseDao<E,W,R,?,?> ownerDao, Converter<W,R> ownerConverter, DataStoreContext context) Converts the storable object to a transportable.
T	convert(P source, R owner) Converts the storable object to a transportable.
P	create(T transportable, W owner, DataStoreContext context) Creates a new persistent object with the data from the given transport object.
protected abstract P	createStorableInstance(T transportable, W owner) Creates the instance of the persistent object (Entity).
protected abstract Q	doConvert(P source) Converts the persistent object to a transport object.
protected abstract T	doConvert(P source, R owner) Converts the persistent object to a transport object.
protected abstract T	findDependent(I dependentId, R owner) Finds a dependent with the given id.
void	update(P target, T source, DataStoreContext context) Updates the persistent object related to the given transport object.
P	update(Q transportable, DataStoreContext context) Updates the persistent object related to the given transport object.

Methods inherited from class com.hp.util.dao.AbstractBaseDao

count, find, find, findAll, get, getQueryPredicate, getQueryPredicateGenerator, getSingularAttribute, updateDependents

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface com.hp.util.dao.BaseDao

count, find, find, findAll, get

Constructor Detail

AbstractBidirectionalDependentDao

protected AbstractBidirectionalDependentDao(Class<P> entityClass)

Construct DAO and initialize query predicate generator.

Parameters:

entityClass - persistent object class.

AbstractBidirectionalDependentDao

protected AbstractBidirectionalDependentDao(Class<P> entityClass,
                                 UpdateStrategy<P,T> updateStrategyT,
                                 UpdateStrategy<P,Q> updateStrategyQ)

Construct DAO and initialize query predicate generator.

Parameters:

entityClass - persistent object class.

updateStrategyT - update strategy for the transport object with a reference to the owner.

updateStrategyQ - update strategy for the transport object with a reference to the owner's id.

Method Detail

create

public P create(T transportable,
       W owner,
       DataStoreContext context)

Description copied from interface: BidirectionalDependentDao

Creates a new persistent object with the data from the given transport object.

Specified by:

create in interface BidirectionalDependentDao<I extends Serializable,P extends Storable<I> & Dependable<E>,T extends Transportable<? super T,I> & Dependent<R>,Q extends Transportable<? super Q,I> & Dependent<E>,F,S,E extends Serializable,W extends Storable<E>,R extends Transportable<? super R,E>>

Parameters:

transportable - transport object to get the data from.

owner - owner

context - data store context

Returns:

the new created persistent object

update

public void update(P target,
          T source,
          DataStoreContext context)

Description copied from interface: BidirectionalDependentDao

Updates the persistent object related to the given transport object. This method is meant to be called by the owner. No need to re-load the dependent storable since the owner already loads it.

Specified by:

update in interface BidirectionalDependentDao<I extends Serializable,P extends Storable<I> & Dependable<E>,T extends Transportable<? super T,I> & Dependent<R>,Q extends Transportable<? super Q,I> & Dependent<E>,F,S,E extends Serializable,W extends Storable<E>,R extends Transportable<? super R,E>>

Parameters:

target - object to update

source - object to take the data from

context - data store context

update

public P update(Q transportable,
       DataStoreContext context)

Description copied from interface: BidirectionalDependentDao

Updates the persistent object related to the given transport object.

Specified by:

update in interface BidirectionalDependentDao<I extends Serializable,P extends Storable<I> & Dependable<E>,T extends Transportable<? super T,I> & Dependent<R>,Q extends Transportable<? super Q,I> & Dependent<E>,F,S,E extends Serializable,W extends Storable<E>,R extends Transportable<? super R,E>>

Parameters:

transportable - transport object to get the data from

context - data store context

Returns:

the updated persistent object

convert

public Q convert(P source)

Description copied from interface: Converter

Converts an instance of type S to an instance of type T

Specified by:

convert in interface Converter<P extends Storable<I> & Dependable<E>,Q extends Transportable<? super Q,I> & Dependent<E>>

Parameters:

source - the source object to be converted

Returns:

an instance of the target type T converted from the source

convert

public T convert(P source,
        R owner)

Description copied from interface: BidirectionalDependentDao

Converts the storable object to a transportable.

Specified by:

convert in interface BidirectionalDependentDao<I extends Serializable,P extends Storable<I> & Dependable<E>,T extends Transportable<? super T,I> & Dependent<R>,Q extends Transportable<? super Q,I> & Dependent<E>,F,S,E extends Serializable,W extends Storable<E>,R extends Transportable<? super R,E>>

Parameters:

source - storable object to convert

owner - the storable object's owner

Returns:

the transport object representing the state of the given storable

convert

public T convert(P storable,
        BaseDao<E,W,R,?,?> ownerDao,
        Converter<W,R> ownerConverter,
        DataStoreContext context)

Description copied from interface: BidirectionalDependentDao

Converts the storable object to a transportable. This call will load the owner from the database.

Example when owner is a Dao

 Dao<E, W, R, ?, ?> ownerDao = ...;
 BidirectionalDependentDao<I, P, T, ?, ?, ?, E, W, R> dependentDao = ...;
 DataStoreContext context = ...;
 P storable = ...;
 T transportable = dependentDao.convert(storable, ownerDao, ownerDao, context);
 

Example when owner is a BidirectionalDependentDao

 final Dao<H, M, N, ?, ?> rootOwnerDao = ...;
 final BidirectionalDependentDao<E, W, R, ?, ?, ?, H, M, N> dependentOwnerDao = ...;
 BidirectionalDependentDao<I, P, T, ?, ?, ?, E, W, R> dependentDao = ...;
 final DataStoreContext context = ...;
 
 Converter<W, R> dependentOwnerConverter = new Converter<W, R>() {
     @Override
     public R convert(W source) {
         return dependentOwnerDao.convert(source, rootOwnerDao, rootOwnerDao, context);
     }
 }; 
 
 P storable = ...;
 T transportable = dependentDao.convert(storable, dependentOwnerDao, dependentOwnerConverter, context);
 

Specified by:

convert in interface BidirectionalDependentDao<I extends Serializable,P extends Storable<I> & Dependable<E>,T extends Transportable<? super T,I> & Dependent<R>,Q extends Transportable<? super Q,I> & Dependent<E>,F,S,E extends Serializable,W extends Storable<E>,R extends Transportable<? super R,E>>

Parameters:

storable - storable object to convert

ownerDao - owner dao to load the owner from the database

ownerConverter - converter to use to convert the owner persistent object to a transport object

context - data store context

Returns:

the transport object representing the state of the given storable

createStorableInstance

protected abstract P createStorableInstance(T transportable,
                       W owner)

Creates the instance of the persistent object (Entity).

Parameters:

transportable - transport object to get the data from.

owner - owner.

Returns:

a new instance of the persistent object.

doConvert

protected abstract Q doConvert(P source)

Converts the persistent object to a transport object.

Parameters:

source - persistent object to convert.

Returns:

a transport object with the same data than source

doConvert

protected abstract T doConvert(P source,
          R owner)

Converts the persistent object to a transport object.

Parameters:

source - persistent object to convert.

owner - owner.

Returns:

a transport object with the same data than source

conformT

protected abstract void conformT(P target,
            T source)

Synchronizes the transport object and the persistent object state. This method is called from update(Transportable, DataStoreContext), thus if update(Transportable, DataStoreContext) is overwritten this method could have an empty implementation.

Parameters:

target - object to update.

source - object to take the data from.

conformQ

protected abstract void conformQ(P target,
            Q source)

Synchronizes the transport object and the persistent object state. This method is called from update(Transportable, DataStoreContext), thus if update(Transportable, DataStoreContext) is overwritten this method could have an empty implementation.

Parameters:

target - object to update.

source - object to take the data from.

findDependent

protected abstract T findDependent(I dependentId,
              R owner)

Finds a dependent with the given id.

Parameters:

dependentId - id of the dependent to find.

owner - owner to search into.

Returns:

the dependent with the given id if found, null otherwise.