Github user chinmaykolhatkar commented on a diff in the pull request:
https://github.com/apache/incubator-apex-malhar/pull/219#discussion_r58043245
--- Diff:
contrib/src/main/java/com/datatorrent/contrib/parquet/AbstractParquetFileReader.java
---
@@ -0,0 +1,113 @@
+/**
+ * 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 com.datatorrent.contrib.parquet;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+import org.apache.hadoop.fs.Path;
+
+import com.datatorrent.api.Context.OperatorContext;
+import com.datatorrent.lib.io.fs.AbstractFileInputOperator;
+
+import parquet.example.data.Group;
+import parquet.hadoop.ParquetReader;
+import parquet.hadoop.example.GroupReadSupport;
+import parquet.schema.MessageType;
+import parquet.schema.MessageTypeParser;
+
+/**
+ * Base implementation of ParquetFileReader. Reads parquet files from input
+ * directory using GroupReadSupport. Derived classes need to implement
+ * {@link #convertGroup(Group)} method to convert Group to other type.
Example
+ * of such implementation is {@link ParquetFilePOJOReader} that converts
Group
+ * to POJO.
+ *
+ * @since 3.3.3
+ */
+public abstract class AbstractParquetFileReader<T> extends
AbstractFileInputOperator<T>
+{
+ private transient ParquetReader<Group> reader;
+ protected transient MessageType schema;
+ protected String parquetSchema;
+
+ @Override
+ public void setup(OperatorContext context)
+ {
+ super.setup(context);
+ schema = MessageTypeParser.parseMessageType(parquetSchema);
+ }
+
+ /**
+ * Opens the file to read using GroupReadSupport
+ */
+ @Override
+ protected InputStream openFile(Path path) throws IOException
+ {
+ InputStream is = super.openFile(path);
+ GroupReadSupport readSupport = new GroupReadSupport();
+ readSupport.init(configuration, null, schema);
+ reader = new ParquetReader<Group>(path, readSupport);
+ return is;
+ }
+
+ /**
+ * Reads next record in parquet file as a group. Returns null when end
of file
+ * is reached
+ */
+ @Override
+ protected T readEntity() throws IOException
+ {
+ Group group = reader.read();
+ if (group != null) {
+ return convertGroup(group);
+ }
+ return null;
+ }
+
+ /**
+ * Converts Group to object of type T. Derived classes need to provide
+ * implementation for conversion
+ *
+ * @param Group
+ * @return object of type T
+ */
+ protected abstract T convertGroup(Group group);
+
+ /**
+ * Get Parquet Schema
+ *
+ * @return parquetSchema
--- End diff --
Description missing for parquetSchema.. Same in setter method.
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