Package javax.jdo.identity
Class SingleFieldIdentity
- java.lang.Object
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- javax.jdo.identity.SingleFieldIdentity
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- 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
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Field Summary
Fields Modifier and Type Field Description protected int
hashCode
The hashCode.protected Object
keyAsObject
The key as an Object.protected static I18NHelper
msg
The Internationalization message helper.
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Constructor Summary
Constructors Modifier Constructor Description SingleFieldIdentity()
Constructor only for Externalizable.protected
SingleFieldIdentity(Class pcClass)
Constructor with target class.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description 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
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Methods inherited from interface java.lang.Comparable
compareTo
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Field Detail
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msg
protected static I18NHelper msg
The Internationalization message helper.
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hashCode
protected int hashCode
The hashCode.
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keyAsObject
protected Object keyAsObject
The key as an Object.
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Constructor Detail
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SingleFieldIdentity
protected SingleFieldIdentity(Class pcClass)
Constructor with target class.- Parameters:
pcClass
- the class of the target- Since:
- 2.0
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SingleFieldIdentity
public SingleFieldIdentity()
Constructor only for Externalizable.- Since:
- 2.0
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Method Detail
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setKeyAsObject
protected void setKeyAsObject(Object key)
Set the given key as the key for this instance. Compute the hash code for the instance.- Parameters:
key
- The key to use- Since:
- 2.0
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assertKeyNotNull
protected void assertKeyNotNull(Object key)
Assert that the key is not null. Throw a JDONullIdentityException if the given key is null.- Parameters:
key
- The key to check- Since:
- 2.0
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getTargetClass
public Class getTargetClass()
Return the target class.- Returns:
- the target class.
- Since:
- 2.0
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getTargetClassName
public String getTargetClassName()
Return the target class name.- Returns:
- the target class name.
- Since:
- 2.0
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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
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createKeyAsObject
protected Object createKeyAsObject()
Create the key as an Object.- Returns:
- the key as an Object;
- Since:
- 2.0
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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.
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hashClassName
protected int hashClassName()
Return the hash code of the class name.- Returns:
- the hash code of the class name
- Since:
- 2.0
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hashCode
public int hashCode()
Return the cached hash code.
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writeExternal
public void writeExternal(ObjectOutput out) throws IOException
Write to the output stream.- Specified by:
writeExternal
in interfaceExternalizable
- Parameters:
out
- the stream- Throws:
IOException
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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 interfaceExternalizable
- Throws:
IOException
ClassNotFoundException
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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
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