org.apache.flink.runtime.io.network.api.reader.RecordReader Maven / Gradle / Ivy
/*
* 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.runtime.io.network.api.reader;
import org.apache.flink.core.io.IOReadableWritable;
import org.apache.flink.runtime.io.network.partition.consumer.InputGate;
import java.io.IOException;
/**
* Record oriented reader for immutable types.
*
* @param Thy type of the records that is read.
*/
public class RecordReader extends AbstractRecordReader implements Reader {
private final Class recordType;
private T currentRecord;
/**
* Creates a new RecordReader that de-serializes records from the given input gate and
* can spill partial records to disk, if they grow large.
*
* @param inputGate The input gate to read from.
* @param tmpDirectories The temp directories. USed for spilling if the reader concurrently
* reconstructs multiple large records.
*/
public RecordReader(InputGate inputGate, Class recordType, String[] tmpDirectories) {
super(inputGate, tmpDirectories);
this.recordType = recordType;
}
@Override
public boolean hasNext() throws IOException, InterruptedException {
if (currentRecord != null) {
return true;
}
else {
T record = instantiateRecordType();
if (getNextRecord(record)) {
currentRecord = record;
return true;
}
else {
return false;
}
}
}
@Override
public T next() throws IOException, InterruptedException {
if (hasNext()) {
T tmp = currentRecord;
currentRecord = null;
return tmp;
}
else {
return null;
}
}
@Override
public void clearBuffers() {
super.clearBuffers();
}
private T instantiateRecordType() {
try {
return recordType.newInstance();
}
catch (InstantiationException | IllegalAccessException e) {
throw new RuntimeException("Cannot instantiate class " + recordType.getName(), e);
}
}
}