org.rocksdb.AbstractNativeReference Maven / Gradle / Ivy
// Copyright (c) 2016, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
package org.rocksdb;
/**
* AbstractNativeReference is the base-class of all RocksDB classes that have
* a pointer to a native C++ {@code rocksdb} object.
*
* AbstractNativeReference has the {@link AbstractNativeReference#close()}
* method, which frees its associated C++ object.
*
* This function should be called manually, or even better, called implicitly using a
* try-with-resources
* statement, when you are finished with the object. It is no longer
* called automatically during the regular Java GC process via finalization
* {@link AbstractNativeReference#finalize()}.
* which is deprecated from Java 9.
*
* Explanatory note - When or if the Garbage Collector calls {@link Object#finalize()}
* depends on the JVM implementation and system conditions, which the programmer
* cannot control. In addition, the GC cannot see through the native reference
* long member variable (which is the C++ pointer value to the native object),
* and cannot know what other resources depend on it.
*
*/
public abstract class AbstractNativeReference implements AutoCloseable {
/**
* Returns true if we are responsible for freeing the underlying C++ object
*
* @return true if we are responsible to free the C++ object
*/
protected abstract boolean isOwningHandle();
/**
* Frees the underlying C++ object
*
* It is strong recommended that the developer calls this after they
* have finished using the object.
*
* Note, that once an instance of {@link AbstractNativeReference} has been
* closed, calling any of its functions will lead to undefined
* behavior.
*/
@Override public abstract void close();
}