javax.jdo.identity
Class SingleFieldIdentity

java.lang.Object
  javax.jdo.identity.SingleFieldIdentity

All Implemented Interfaces:

Externalizable, Serializable, Comparable

Direct Known Subclasses:

ByteIdentity, CharIdentity, IntIdentity, LongIdentity, ObjectIdentity, ShortIdentity, StringIdentity

public abstract class SingleFieldIdentity
extends Object
implements Externalizable, Comparable

This class is the abstract base class for all single field identity classes. A common case of application identity uses exactly one persistent field in the class to represent identity. In this case, the application can use a standard JDO class instead of creating a new user-defined class for the purpose.

Version:

2.0

See Also:

Serialized Form

Field Summary

protected int	hashCode The hashCode.
protected Object	keyAsObject The key as an Object.
protected static I18NHelper	msg The Internationalization message helper.

Constructor Summary

	SingleFieldIdentity() Constructor only for Externalizable.
protected	SingleFieldIdentity(Class pcClass) Constructor with target class.

Method Summary

protected void	assertKeyNotNull(Object key) Assert that the key is not null.
protected int	compare(SingleFieldIdentity o) Determine the ordering of identity objects.
protected Object	createKeyAsObject() Create the key as an Object.
boolean	equals(Object obj) Check the class and class name and object type.
Object	getKeyAsObject() Return the key as an Object.
Class	getTargetClass() Return the target class.
String	getTargetClassName() Return the target class name.
protected int	hashClassName() Return the hash code of the class name.
int	hashCode() Return the cached hash code.
void	readExternal(ObjectInput in) Read from the input stream.
protected void	setKeyAsObject(Object key) Set the given key as the key for this instance.
void	writeExternal(ObjectOutput out) Write to the output stream.

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.lang.Comparable

compareTo

Field Detail

msg

protected static I18NHelper msg

The Internationalization message helper.

hashCode

protected int hashCode

The hashCode.

keyAsObject

protected Object keyAsObject

The key as an Object.

Constructor Detail

SingleFieldIdentity

protected SingleFieldIdentity(Class pcClass)

Constructor with target class.

Parameters:

pcClass - the class of the target

Since:

2.0

SingleFieldIdentity

public SingleFieldIdentity()

Constructor only for Externalizable.

Since:

2.0

Method Detail

setKeyAsObject

protected void setKeyAsObject(Object key)

Set the given key as the key for this instance. Compute the hash code for the instance.

Since:

2.0

assertKeyNotNull

protected void assertKeyNotNull(Object key)

Assert that the key is not null. Throw a JDONullIdentityException if the given key is null.

Since:

2.0

getTargetClass

public Class getTargetClass()

Return the target class.

Returns:

the target class.

Since:

2.0

getTargetClassName

public String getTargetClassName()

Return the target class name.

Returns:

the target class name.

Since:

2.0

getKeyAsObject

public Object getKeyAsObject()

Return the key as an Object. The method is synchronized to avoid race conditions in multi-threaded environments.

Returns:

the key as an Object.

Since:

2.0

createKeyAsObject

protected Object createKeyAsObject()

Create the key as an Object.

Returns:

the key as an Object;

Since:

2.0

equals

public boolean equals(Object obj)

Check the class and class name and object type. If restored from serialization, class will be null so compare class name.

Overrides:

equals in class Object

Parameters:

obj - the other object

Returns:

true if the class or class name is the same

hashClassName

protected int hashClassName()

Return the hash code of the class name.

Returns:

the hash code of the class name

Since:

2.0

hashCode

public int hashCode()

Return the cached hash code.

Overrides:

hashCode in class Object

Returns:

the cached hash code.

writeExternal

public void writeExternal(ObjectOutput out)
                   throws IOException

Write to the output stream.

Specified by:

writeExternal in interface Externalizable

Parameters:

out - the stream

Throws:

IOException

readExternal

public void readExternal(ObjectInput in)
                  throws IOException,
                         ClassNotFoundException

Read from the input stream. Creates a new instance with the target class name set

Specified by:

readExternal in interface Externalizable

Throws:

IOException

ClassNotFoundException

compare

protected int compare(SingleFieldIdentity o)

Determine the ordering of identity objects. Only the class name is compared. This method is only used by subclasses.

Parameters:

o - Other identity

Returns:

The relative ordering between the objects

Since:

2.2