org.rocksdb

Class RocksObject

java.lang.Object

org.rocksdb.RocksObject

Direct Known Subclasses:

AbstractComparator, BackupableDBOptions, Checkpoint, ColumnFamilyHandle, ColumnFamilyOptions, ComparatorOptions, DBOptions, DirectSlice, Filter, FlushOptions, Options, ReadOptions, RestoreBackupableDB, RestoreOptions, RocksDB, RocksEnv, RocksIterator, Slice, Snapshot, WriteBatch, WriteBatch.Handler, WriteOptions

public abstract class RocksObject
extends java.lang.Object

RocksObject is the base-class of all RocksDB classes that has a pointer to some c++ rocksdb object.

RocksObject has dispose() function, which releases its associated c++ resource.

This function can be either called manually, or being called automatically during the regular Java GC process. However, since Java may wrongly assume a RocksObject only contains a long member variable and think it is small in size, Java may give RocksObject low priority in the GC process. For this, it is suggested to call dispose() manually. However, it is safe to let RocksObject go out-of-scope without manually calling dispose() as dispose() will be called in the finalizer during the regular GC process.

Field Summary

Fields

Modifier and Type	Field and Description
protected long	nativeHandle_ A long variable holding c++ pointer pointing to some RocksDB C++ object.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	RocksObject()

Method Summary

Modifier and Type	Method and Description
protected void	disOwnNativeHandle() Revoke ownership of the native object.
void	dispose() Release the c++ object manually pointed by the native handle.
protected abstract void	disposeInternal() The helper function of dispose() which all subclasses of RocksObject must implement to release their associated C++ resource.
protected void	finalize() Simply calls dispose() and release its c++ resource if it has not yet released.
protected boolean	isInitialized() Returns true if the associated native handle has been initialized.
protected boolean	isOwningNativeHandle() Returns true if the current RocksObject is responsible to release its native handle.

Methods inherited from class java.lang.Object

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

Field Detail

nativeHandle_

protected long nativeHandle_

A long variable holding c++ pointer pointing to some RocksDB C++ object.

Constructor Detail

RocksObject

protected RocksObject()

Method Detail

dispose

public final void dispose()

Release the c++ object manually pointed by the native handle.

Note that dispose() will also be called during the GC process if it was not called before its RocksObject went out-of-scope. However, since Java may wrongly wrongly assume those objects are small in that they seems to only hold a long variable. As a result, they might have low priority in the GC process. To prevent this, it is suggested to call dispose() manually.

Note that once an instance of RocksObject has been disposed, calling its function will lead undefined behavior.

disposeInternal

protected abstract void disposeInternal()

The helper function of dispose() which all subclasses of RocksObject must implement to release their associated C++ resource.

disOwnNativeHandle

protected void disOwnNativeHandle()

Revoke ownership of the native object.

This will prevent the object from attempting to delete the underlying native object in its finalizer. This must be used when another object takes over ownership of the native object or both will attempt to delete the underlying object when garbage collected.

When disOwnNativeHandle() is called, dispose() will simply set nativeHandle_ to 0 without releasing its associated C++ resource. As a result, incorrectly use this function may cause memory leak, and this function call will not affect the return value of isInitialized().

See Also:

dispose(), isInitialized()

isOwningNativeHandle

protected boolean isOwningNativeHandle()

Returns true if the current RocksObject is responsible to release its native handle.

Returns:

true if the current RocksObject is responsible to release its native handle.

See Also:

disOwnNativeHandle(), dispose()

isInitialized

protected boolean isInitialized()

Returns true if the associated native handle has been initialized.

Returns:

true if the associated native handle has been initialized.

See Also:

dispose()

finalize

protected void finalize()
                 throws java.lang.Throwable

Simply calls dispose() and release its c++ resource if it has not yet released.

Overrides:

finalize in class java.lang.Object

Throws:

java.lang.Throwable