com.googlecode.objectify

Class Ref<T>

java.lang.Object

com.googlecode.objectify.Ref<T>

All Implemented Interfaces:

Serializable, Comparable<Ref<T>>

Direct Known Subclasses:

DeadRef, LiveRef

public abstract class Ref<T>
extends Object
implements Serializable, Comparable<Ref<T>>

Ref is a Key which allows the entity value to be fetched directly.

Note that the methods might or might not throw runtime exceptions related to datastore operations; ConcurrentModificationException, DatastoreTimeoutException, DatastoreFailureException, and DatastoreNeedIndexException. Some Refs hide datastore operations that could throw these exceptions.

Author:

Jeff Schnitzer

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected Key<T>	key The key associated with this ref

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	Ref() For GWT serialization
protected	Ref(Key<T> key) Create a Ref based on the key, with the specified session

Method Summary

Methods

Modifier and Type	Method and Description
int	compareTo(Ref<T> o) Comparison is based on key
static <T> Ref<T>	create(Key<T> key) Key.create(Blah.class, id) is easier to type than new Key(Blah.class, id)
static <T> Ref<T>	create(T value) Creates a Ref from a registered pojo entity
boolean	equals(Object obj) Equality comparison is based on key equivalence
boolean	equivalent(Key<T> other) Type safe comparison for key equivalence
boolean	equivalent(Ref<T> other) Type-safe comparison for key equivalence
abstract T	get() Obtain the entity value associated with the key.
Key<T>	getKey() Same as key() but conforms to JavaBeans conventions in case this is being processed by a JSON converter or expression language.
T	getValue() This method exists to facilitate serialization via javabeans conventions.
int	hashCode() Hash code is simply that of key
abstract boolean	isLoaded() If an entity has been loaded into the session or is otherwise available, this will return true.
Key<T>	key()
T	safe() Obtain the entity value, throwing an exception if the entity was not found.
T	safeGet() Deprecated.
String	toString() Renders some info about the key

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

key

protected Key<T> key

The key associated with this ref

Constructor Detail

Ref

protected Ref()

For GWT serialization

Ref

protected Ref(Key<T> key)

Create a Ref based on the key, with the specified session

Method Detail

create

public static <T> Ref<T> create(Key<T> key)

Key.create(Blah.class, id) is easier to type than new Key(Blah.class, id)

create

public static <T> Ref<T> create(T value)

Creates a Ref from a registered pojo entity

key

public Key<T> key()

Returns:

the key associated with this Ref

get

public abstract T get()

Obtain the entity value associated with the key. Will pull from session if present, otherwise will fetch from the datastore.

Returns:

the entity referenced, or null if the entity was not found

isLoaded

public abstract boolean isLoaded()

If an entity has been loaded into the session or is otherwise available, this will return true. Calls to get() will not require a trip to backing store. Note that even when loaded, get() can still return null if there is no entity which corresponds to the key.

Returns:

true if the value is in the session or otherwise immediately available; false if get() will require a trip to the datastore or memcache.

getValue

public final T getValue()

This method exists to facilitate serialization via javabeans conventions. Unlike get(), it will return null if isLoaded() is false.

Returns:

the entity referenced, or null if either the entity was not found or isLoaded() is false.

getKey

public final Key<T> getKey()

Same as key() but conforms to JavaBeans conventions in case this is being processed by a JSON converter or expression language.

safe

public final T safe()
             throws NotFoundException

Obtain the entity value, throwing an exception if the entity was not found.

Returns:

the entity referenced. Never returns null.

Throws:

NotFoundException - if the specified entity was not found

safeGet

@Deprecated
public final T safeGet()
                throws NotFoundException

Deprecated.

Use safe() instead.

Throws:

NotFoundException

compareTo

public int compareTo(Ref<T> o)

Comparison is based on key

Specified by:

compareTo in interface Comparable<Ref<T>>

equals

public boolean equals(Object obj)

Equality comparison is based on key equivalence

Overrides:

equals in class Object

equivalent

public boolean equivalent(Ref<T> other)

Type-safe comparison for key equivalence

equivalent

public boolean equivalent(Key<T> other)

Type safe comparison for key equivalence

hashCode

public int hashCode()

Hash code is simply that of key

Overrides:

hashCode in class Object

toString

public String toString()

Renders some info about the key

Overrides:

toString in class Object