[Java] Generalize dis-own native handle and refine dispose framework.

Summary:
1. Move disOwnNativeHandle() function from RocksDB to RocksObject
to allow other RocksObject to use disOwnNativeHandle() when its
ownership of native handle has been transferred.

2. RocksObject now has an abstract implementation of dispose(),
which does the following two things.  First, it checks whether
both isOwningNativeHandle() and isInitialized() return true.
If so, it will call the protected abstract function dispose0(),
which all the subclasses of RocksObject should implement.  Second,
it sets nativeHandle_ = 0.  This redesign ensure all subclasses
of RocksObject have the same dispose behavior.

3. All subclasses of RocksObject now should implement dispose0()
instead of dispose(), and dispose0() will be called only when
isInitialized() returns true.

Test Plan:
make rocksdbjava
make jtest

Reviewers: dhruba, sdong, ankgup87, rsumbaly, swapnilghike, zzbennett, haobo

Reviewed By: haobo

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D18801

java/rocksjni/backupablejni.cc

@@ -72,10 +72,10 @@ jstring Java_org_rocksdb_BackupableDBOptions_backupDir(
 
 /*
  * Class:     org_rocksdb_BackupableDBOptions
- * Method:    dispose
+ * Method:    disposeInternal
  * Signature: (J)V
  */
-void Java_org_rocksdb_BackupableDBOptions_dispose(
+void Java_org_rocksdb_BackupableDBOptions_disposeInternal(
     JNIEnv* env, jobject jopt, jlong jhandle) {
   auto bopt = reinterpret_cast<rocksdb::BackupableDBOptions*>(jhandle);
   assert(bopt);

java/rocksjni/filter.cc

@@ -29,13 +29,10 @@ void Java_org_rocksdb_BloomFilter_createNewFilter0(
 
 /*
  * Class:     org_rocksdb_Filter
- * Method:    dispose0
+ * Method:    disposeInternal
  * Signature: (J)V
  */
-void Java_org_rocksdb_Filter_dispose0(
+void Java_org_rocksdb_Filter_disposeInternal(
     JNIEnv* env, jobject jobj, jlong handle) {
-  auto fp = reinterpret_cast<rocksdb::FilterPolicy*>(handle);
-  delete fp;
-
-  rocksdb::FilterJni::setHandle(env, jobj, nullptr);
+  delete reinterpret_cast<rocksdb::FilterPolicy*>(handle);
 }

java/rocksjni/iterator.cc

@@ -135,10 +135,10 @@ void Java_org_rocksdb_RocksIterator_status0(
 
 /*
  * Class:     org_rocksdb_RocksIterator
- * Method:    dispose
+ * Method:    disposeInternal
  * Signature: (J)V
  */
-void Java_org_rocksdb_RocksIterator_dispose(
+void Java_org_rocksdb_RocksIterator_disposeInternal(
     JNIEnv* env, jobject jobj, jlong handle) {
   auto it = reinterpret_cast<rocksdb::Iterator*>(handle);
   delete it;

java/rocksjni/options.cc

@@ -35,14 +35,12 @@ void Java_org_rocksdb_Options_newOptions(JNIEnv* env, jobject jobj) {
 
 /*
  * Class:     org_rocksdb_Options
- * Method:    dispose0
- * Signature: ()V
+ * Method:    disposeInternal
+ * Signature: (J)V
  */
-void Java_org_rocksdb_Options_dispose0(JNIEnv* env, jobject jobj) {
-  rocksdb::Options* op = rocksdb::OptionsJni::getHandle(env, jobj);
-  delete op;
-
-  rocksdb::OptionsJni::setHandle(env, jobj, nullptr);
+void Java_org_rocksdb_Options_disposeInternal(
+    JNIEnv* env, jobject jobj, jlong handle) {
+  delete reinterpret_cast<rocksdb::Options*>(handle);
 }
 
 /*
@@ -1665,10 +1663,10 @@ void Java_org_rocksdb_WriteOptions_newWriteOptions(
 
 /*
  * Class:     org_rocksdb_WriteOptions
- * Method:    dispose0
+ * Method:    disposeInternal
  * Signature: ()V
  */
-void Java_org_rocksdb_WriteOptions_dispose0(
+void Java_org_rocksdb_WriteOptions_disposeInternal(
     JNIEnv* env, jobject jwrite_options, jlong jhandle) {
   auto write_options = reinterpret_cast<rocksdb::WriteOptions*>(jhandle);
   delete write_options;
@@ -1732,10 +1730,10 @@ void Java_org_rocksdb_ReadOptions_newReadOptions(
 
 /*
  * Class:     org_rocksdb_ReadOptions
- * Method:    dispose
+ * Method:    disposeInternal
  * Signature: (J)V
  */
-void Java_org_rocksdb_ReadOptions_dispose(
+void Java_org_rocksdb_ReadOptions_disposeInternal(
     JNIEnv* env, jobject jobj, jlong jhandle) {
   delete reinterpret_cast<rocksdb::ReadOptions*>(jhandle);
   rocksdb::ReadOptionsJni::setHandle(env, jobj, nullptr);

java/rocksjni/rocksjni.cc

@@ -419,14 +419,12 @@ void Java_org_rocksdb_RocksDB_remove__JJ_3BI(
 
 /*
  * Class:     org_rocksdb_RocksDB
- * Method:    dispose
+ * Method:    disposeInternal
  * Signature: (J)V
  */
-void Java_org_rocksdb_RocksDB_dispose(
+void Java_org_rocksdb_RocksDB_disposeInternal(
     JNIEnv* env, jobject java_db, jlong jhandle) {
-  auto db = reinterpret_cast<rocksdb::DB*>(jhandle);
-  assert(db != nullptr);
-  delete db;
+  delete reinterpret_cast<rocksdb::DB*>(jhandle);
 }
 
 /*

java/rocksjni/write_batch.cc

@@ -134,15 +134,12 @@ void Java_org_rocksdb_WriteBatch_putLogData(
 
 /*
  * Class:     org_rocksdb_WriteBatch
- * Method:    dispose0
- * Signature: ()V
+ * Method:    disposeInternal
+ * Signature: (J)V
  */
-void Java_org_rocksdb_WriteBatch_dispose0(JNIEnv* env, jobject jobj) {
-  rocksdb::WriteBatch* wb = rocksdb::WriteBatchJni::getHandle(env, jobj);
-  assert(wb != nullptr);
-  delete wb;
-
-  rocksdb::WriteBatchJni::setHandle(env, jobj, nullptr);
+void Java_org_rocksdb_WriteBatch_disposeInternal(
+    JNIEnv* env, jobject jobj, jlong handle) {
+  delete reinterpret_cast<rocksdb::WriteBatch*>(handle);
 }
 
 /*