/
ResultOutput.java
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/
ResultOutput.java
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/**
* Copyright 2011-2012 Asakusa Framework Team.
*
* Licensed 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.asakusafw.runtime.flow;
import java.io.IOException;
import java.util.Collections;
import java.util.List;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.mapreduce.Counter;
import org.apache.hadoop.mapreduce.RecordWriter;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import com.asakusafw.runtime.core.Result;
/**
* 結果を出力する。
* @param <T> 結果の型
* @since 0.1.0
* @since 0.2.5
*/
public class ResultOutput<T> implements Result<T> {
static final Log LOG = LogFactory.getLog(ResultOutput.class);
private final TaskAttemptContext context;
private final RecordWriter<Object, Object> writer;
private final List<Counter> counters;
private long records;
/**
* インスタンスを生成する。
* @param context 現在のコンテキスト
* @param writer 結果の出力先
* @throws IOException 初期化に失敗した場合
* @throws InterruptedException 初期化に失敗した場合
* @throws IllegalArgumentException 引数に{@code null}が指定された場合
*/
@SuppressWarnings({ "rawtypes" })
public ResultOutput(
TaskAttemptContext context,
RecordWriter writer) throws IOException, InterruptedException {
this(context, writer, Collections.<Counter>emptyList());
}
/**
* Creates a new instance.
* @param context current context
* @param writer target writer
* @param counters record counters
* @throws IOException if initialization failed by I/O exception
* @throws InterruptedException if interrupted
* @throws IllegalArgumentException if some parameters were {@code null}
* @since 0.2.5
*/
@SuppressWarnings({ "rawtypes", "unchecked" })
public ResultOutput(
TaskAttemptContext context,
RecordWriter writer,
List<Counter> counters) throws IOException, InterruptedException {
if (context == null) {
throw new IllegalArgumentException("context must not be null"); //$NON-NLS-1$
}
if (writer == null) {
throw new IllegalArgumentException("writer must not be null"); //$NON-NLS-1$
}
if (counters == null) {
throw new IllegalArgumentException("counters must not be null"); //$NON-NLS-1$
}
this.context = context;
this.writer = writer;
this.counters = counters;
}
@Override
public void add(T result) {
try {
writer.write(getKey(result), result);
records++;
} catch (Exception e) {
throw new Result.OutputException(e);
}
}
/**
* Returns a key for the value.
* @param result target value
* @return a corresponded key
*/
protected Object getKey(T result) {
return NullWritable.get();
}
/**
* 現在の出力を破棄する。
* @throws IOException 出力のフラッシュに失敗した場合
* @throws InterruptedException 出力の破棄に割り込みが発行された場合
* @throws IllegalArgumentException 引数に{@code null}が含まれる場合
*/
public void close() throws IOException, InterruptedException {
for (Counter counter : counters) {
counter.increment(records);
}
writer.close(context);
}
}