[GitHub] [jackrabbit-oak] nfsantos commented on a diff in pull request #1123: OAK-10429: Implementation for IncrementalFFS

["nfsantos (via GitHub)" <gi...@apache.org>]

nfsantos commented on code in PR #1123:
URL: https://github.com/apache/jackrabbit-oak/pull/1123#discussion_r1335615576


##########
oak-run-commons/src/main/java/org/apache/jackrabbit/oak/index/indexer/document/indexstore/IndexStoreMetadataOperatorImpl.java:
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@@ -0,0 +1,70 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.jackrabbit.oak.index.indexer.document.indexstore;
+
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.fasterxml.jackson.databind.JavaType;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.apache.jackrabbit.oak.commons.Compression;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.BufferedReader;
+import java.io.BufferedWriter;
+import java.io.File;
+import java.io.IOException;
+
+public class IndexStoreMetadataOperatorImpl<M> implements IndexStoreMetadataOperator<M> {
+    private static final Logger log = LoggerFactory.getLogger(IndexStoreMetadataOperatorImpl.class);
+
+    @Override
+    public File createMetadataFile(M m, File file, Compression algorithm) throws IOException {
+        File metadataFile;
+        if (file.isDirectory()) {
+            metadataFile = new File(file, IndexStoreUtils.getMetadataFileName(algorithm));
+        } else {
+            metadataFile = file;
+        }
+
+        try (BufferedWriter metadataWriter = IndexStoreUtils.createWriter(metadataFile, algorithm)) {
+            writeMetadataToFile(metadataWriter, m);
+        }
+        log.info("Created metadataFile:{} ", metadataFile.getPath());
+        return metadataFile;
+    }
+
+    private void writeMetadataToFile(BufferedWriter bufferedWriter, M m) throws IOException {
+        ObjectMapper mapper = new ObjectMapper();
+        mapper.writeValue(bufferedWriter, m);
+    }
+
+    /*
+        deserialization with generic type doesnot happen automatically. So we explicitly added this 3rd argument to
+        provide JavaType info to jackson.
+     */
+    @Override
+    public M getIndexStoreMetadata(File metadataFile, Compression algorithm, TypeReference<M> clazz) throws IOException {
+        ObjectMapper mapper = new ObjectMapper();

Review Comment:
   ObjectMapper is an expensive object to build. Since it is thread-safe, it is preferable to reuse it. There are a few more similar situations in this PR.



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