Refactor filter impl

java/Makefile

-NATIVE_JAVA_CLASSES = org.rocksdb.RocksDB org.rocksdb.Options org.rocksdb.WriteBatch org.rocksdb.WriteBatchInternal org.rocksdb.WriteBatchTest org.rocksdb.WriteOptions org.rocksdb.BackupableDB org.rocksdb.BackupableDBOptions org.rocksdb.Statistics org.rocksdb.Iterator org.rocksdb.VectorMemTableConfig org.rocksdb.SkipListMemTableConfig org.rocksdb.HashLinkedListMemTableConfig org.rocksdb.HashSkipListMemTableConfig org.rocksdb.PlainTableConfig org.rocksdb.ReadOptions org.rocksdb.Filter
+NATIVE_JAVA_CLASSES = org.rocksdb.RocksDB org.rocksdb.Options org.rocksdb.WriteBatch org.rocksdb.WriteBatchInternal org.rocksdb.WriteBatchTest org.rocksdb.WriteOptions org.rocksdb.BackupableDB org.rocksdb.BackupableDBOptions org.rocksdb.Statistics org.rocksdb.Iterator org.rocksdb.VectorMemTableConfig org.rocksdb.SkipListMemTableConfig org.rocksdb.HashLinkedListMemTableConfig org.rocksdb.HashSkipListMemTableConfig org.rocksdb.PlainTableConfig org.rocksdb.ReadOptions org.rocksdb.Filter org.rocksdb.BloomFilter
 NATIVE_INCLUDE = ./include
 ROCKSDB_JAR = rocksdbjni.jar
 

java/RocksDBSample.java

@@ -32,7 +32,7 @@ public class RocksDBSample {
       assert(db == null);
     }
 
-    Filter filter = new Filter(10);
+    Filter filter = new BloomFilter(10);
     options.setCreateIfMissing(true)
         .createStatistics()
         .setWriteBufferSize(8 * SizeUnit.KB)

java/org/rocksdb/BloomFilter.java

+// Copyright (c) 2014, Facebook, Inc.  All rights reserved.
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree. An additional grant
+// of patent rights can be found in the PATENTS file in the same directory.
+
+package org.rocksdb;
+
+public class BloomFilter extends Filter {
+  private final int bitsPerKey_;
+  
+  public BloomFilter(int bitsPerKey) {
+    super();
+    bitsPerKey_ = bitsPerKey;
+    createNewFilter();
+  }
+  
+  @Override
+  protected void createNewFilter() {
+    createNewFilter0(bitsPerKey_);
+  }
+  
+  private native void createNewFilter0(int bitsKeyKey);
+}
\ No newline at end of file

java/org/rocksdb/Filter.java

@@ -17,12 +17,10 @@ package org.rocksdb;
  * A good value for bitsPerKey is 10, which yields a filter
  * with ~ 1% false positive rate.
  */
-public class Filter {
-  private long nativeHandle_;
-
-  public Filter(int bitsPerKey) {
-    newFilter(bitsPerKey);
-  }
+public abstract class Filter {
+  protected long nativeHandle_ = 0;
+    
+  protected abstract void createNewFilter();
 
   /**
    * Deletes underlying C++ filter pointer.
@@ -37,10 +35,9 @@ public class Filter {
     dispose();
   }
 
-  private boolean isInitialized() {
+  protected boolean isInitialized() {
     return (nativeHandle_ != 0);
   }
 
-  private native void newFilter(int bitsPerKey);
   private native void dispose0(long handle);
 }

java/rocksjni/filter.cc

@@ -12,15 +12,16 @@
 #include <string>
 
 #include "include/org_rocksdb_Filter.h"
+#include "include/org_rocksdb_BloomFilter.h"
 #include "rocksjni/portal.h"
 #include "rocksdb/filter_policy.h"
 
 /*
- * Class:     org_rocksdb_Filter
- * Method:    newFilter
+ * Class:     org_rocksdb_BloomFilter
+ * Method:    createNewFilter0
  * Signature: (I)V
  */
-void Java_org_rocksdb_Filter_newFilter(
+void Java_org_rocksdb_BloomFilter_createNewFilter0(
     JNIEnv* env, jobject jobj, jint bits_per_key) {
   const rocksdb::FilterPolicy* fp = rocksdb::NewBloomFilterPolicy(bits_per_key);
   rocksdb::FilterJni::setHandle(env, jobj, fp);