org.apache.geode

Class CopyHelper

java.lang.Object

org.apache.geode.CopyHelper

public final class CopyHelper
extends Object

A static helper for optimally creating copies. Creating copies of cache values provides improved concurrency as well as isolation. For transactions, creating a copy is the guaranteed way to enforce "Read Committed" isolation on changes to cache Entries.

Here is a simple example of how to use CopyHelper.copy

 Object o = r.get("stringBuf");
 StringBuilder s = (StringBuilder) CopyHelper.copy(o);
 s.append("... and they lived happily ever after.  The End.");
 r.put("stringBuf", s);
 

Since:

GemFire 4.0

See Also:

Cloneable, Serializable, DataSerializer, GemFireCache.setCopyOnRead(boolean), CacheTransactionManager

Method Summary

Modifier and Type	Method and Description
static <T> T	copy(T o) Makes a copy of the specified object.
static <T> T	deepCopy(T o) Makes a deep copy of the specified object o using serialization, so the object has to be serializable by GemFire.
static boolean	isWellKnownImmutableInstance(Object o) Return true if the given object is an instance of a well known immutable class.

Methods inherited from class java.lang.Object

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

Method Detail

isWellKnownImmutableInstance

public static boolean isWellKnownImmutableInstance(Object o)

Return true if the given object is an instance of a well known immutable class. The well known classes are:

• String
• Byte
• Character
• Short
• Integer
• Long
• Float
• Double
• BigInteger
• BigDecimal
• UUID
• PdxInstance but not WritablePdxInstance

Parameters:

o - the object to check

Returns:

true if o is an instance of a well known immutable class.

Since:

GemFire 6.6.2

copy

public static <T> T copy(T o)

Makes a copy of the specified object. The object returned is not guaranteed to be a deep copy of the original object, as explained below.

Copies can only be made if the original is a Cloneable or serializable by GemFire. If o is a well known immutable instance then it will be returned without copying it.

If the argument o is an instance of Cloneable, a copy is made by invoking clone on it. Note that not all implementations of clone make deep copies (e.g. HashMap.clone). Otherwise, if the argument is not an instance of Cloneable, a copy is made using serialization: if GemFire serialization is implemented, it is used; otherwise, java serialization is used.

The difference between this method and deepCopy, is that this method uses clone if available, whereas deepCopy does not. As a result, for Cloneable objects copied using this method, how deep a copy the returned object is depends on its implementation of clone.

Type Parameters:

T - the type of the object to be copied

Parameters:

o - the original object that a copy is needed of

Returns:

the new instance that is a copy of of the original

Throws:

CopyException - if copying fails because a class could not be found or could not be serialized.

Since:

GemFire 4.0

See Also:

deepCopy(Object)

deepCopy

public static <T> T deepCopy(T o)

Makes a deep copy of the specified object o using serialization, so the object has to be serializable by GemFire.

If o is a well known immutable instance then it will be returned without copying it.

The passed in object is serialized in memory, and then deserialized into a new instance, which is returned. If GemFire serialization is implemented for the object, it is used; otherwise, java serialization is used.

Type Parameters:

T - the type of the object to be copied

Parameters:

o - the original object to be copied

Returns:

the new instance that is a copy of the original

Throws:

CopyException - if copying fails because a class could not be found or could not be serialized

See Also:

copy(Object)