| /* |
| * 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.jena.hadoop.rdf.mapreduce; |
| |
| import java.io.IOException; |
| |
| import org.apache.hadoop.mapreduce.Mapper; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| /** |
| * A mapper which swaps the key and value around |
| * |
| * |
| * @param <TKey> Key type |
| * @param <TValue> Value type |
| */ |
| public class SwapMapper<TKey, TValue> extends Mapper<TKey, TValue, TValue, TKey> { |
| private static final Logger LOG = LoggerFactory.getLogger(SwapMapper.class); |
| |
| private boolean tracing = false; |
| |
| @Override |
| protected void setup(Context context) throws IOException, InterruptedException { |
| super.setup(context); |
| this.tracing = LOG.isTraceEnabled(); |
| } |
| |
| @Override |
| protected void map(TKey key, TValue value, Context context) throws IOException, |
| InterruptedException { |
| if (this.tracing) { |
| LOG.trace("Key = {}", key); |
| LOG.trace("Value = {}", value); |
| } |
| context.write(value, key); |
| } |
| |
| } |