[GitHub] azagrebin commented on a change in pull request #5876: [FLINK-9126] New CassandraPojoInputFormat to output data as a custom annotated Cassandra Pojo

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azagrebin commented on a change in pull request #5876: [FLINK-9126] New CassandraPojoInputFormat to output data as a custom annotated Cassandra Pojo
URL: https://github.com/apache/flink/pull/5876#discussion_r207954696
 
 

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 File path: flink-connectors/flink-connector-cassandra/src/main/java/org/apache/flink/batch/connectors/cassandra/CassandraPojoInputFormat.java
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+/*
+ * 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.flink.batch.connectors.cassandra;
+
+import org.apache.flink.api.common.io.DefaultInputSplitAssigner;
+import org.apache.flink.api.common.io.NonParallelInput;
+import org.apache.flink.api.common.io.RichInputFormat;
+import org.apache.flink.api.common.io.statistics.BaseStatistics;
+import org.apache.flink.configuration.Configuration;
+import org.apache.flink.core.io.GenericInputSplit;
+import org.apache.flink.core.io.InputSplit;
+import org.apache.flink.core.io.InputSplitAssigner;
+import org.apache.flink.streaming.connectors.cassandra.ClusterBuilder;
+import org.apache.flink.util.Preconditions;
+
+import org.apache.flink.shaded.guava18.com.google.common.base.Strings;
+
+import com.datastax.driver.core.Cluster;
+import com.datastax.driver.core.Session;
+import com.datastax.driver.mapping.Mapper;
+import com.datastax.driver.mapping.MappingManager;
+import com.datastax.driver.mapping.Result;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+
+/**
+ * InputFormat to read data from Apache Cassandra and generate a custom Cassandra annotated object.
+ * @param <OUT> type of inputClass
+ */
+public class CassandraPojoInputFormat<OUT> extends RichInputFormat<OUT, InputSplit> implements NonParallelInput {
+	private static final Logger LOG = LoggerFactory.getLogger(CassandraInputFormat.class);
+
+	private final String query;
+	private final ClusterBuilder builder;
+
+	private transient Cluster cluster;
+	private transient Session session;
+	private transient Result<OUT> resultSet;
+	private Class<OUT> inputClass;
+
+	public CassandraPojoInputFormat(String query, ClusterBuilder builder, Class<OUT> inputClass) {
+		Preconditions.checkArgument(!Strings.isNullOrEmpty(query), "Query cannot be null or empty");
+		Preconditions.checkArgument(builder != null, "Builder cannot be null");
+		Preconditions.checkArgument(inputClass != null, "InputClass cannot be null");
+
+		this.query = query;
+		this.builder = builder;
+		this.inputClass = inputClass;
+	}
+
+	@Override
+	public void configure(Configuration parameters) {
+		this.cluster = builder.getCluster();
+	}
+
+	@Override
+	public BaseStatistics getStatistics(BaseStatistics cachedStatistics) throws IOException {
+		return cachedStatistics;
+	}
+
+	/**
+	 * Opens a Session and executes the query.
+	 *
+	 * @param ignored
+	 * @throws IOException
+	 */
+	@Override
+	public void open(InputSplit ignored) throws IOException {
+		this.session = cluster.connect();
+		MappingManager manager = new MappingManager(session);
+
+		Mapper<OUT> mapper = manager.mapper(inputClass);
 
 Review comment:
   I would also at least overload the `CassandraPojoInputFormat` constructor with additional parameter which is a factory for `Mapper<OUT>` because now it is hidden in the internals of this class but users might want to configure it in a special way (e.g. `Mapper.setDefaultSaveOptions(...)`), similar to `ClusterBuilder`.

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