Java tutorial
/** * 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. * * Copyright 2013 Josh Elser * */ package cosmos.impl; import java.nio.charset.CharacterCodingException; import java.util.Map.Entry; import org.apache.accumulo.core.data.Key; import org.apache.accumulo.core.data.Value; import org.apache.hadoop.io.Text; import org.apache.hadoop.io.VLongWritable; import com.google.common.base.Function; import com.google.common.base.Preconditions; import com.google.common.collect.Maps; import cosmos.accumulo.GroupByRowSuffixIterator; import cosmos.options.Defaults; import cosmos.records.values.RecordValue; /** * */ public class GroupByFunction implements Function<Entry<Key, Value>, Entry<RecordValue<?>, Long>> { private final Text _holder = new Text(); @Override public Entry<RecordValue<?>, Long> apply(Entry<Key, Value> entry) { String value = getValueFromKey(entry.getKey()); //TODO Add Cache for CV RecordValue<?> val = RecordValue.create(value, entry.getKey().getColumnVisibilityParsed()); VLongWritable writable = GroupByRowSuffixIterator.getWritable(entry.getValue()); return Maps.<RecordValue<?>, Long>immutableEntry(val, writable.get()); } private String getValueFromKey(Key k) { Preconditions.checkNotNull(k); k.getRow(_holder); int index = _holder.find(Defaults.NULL_BYTE_STR); if (-1 == index) { throw new IllegalArgumentException("Found no null byte in key: " + k); } try { return Text.decode(_holder.getBytes(), index + 1, _holder.getLength() - (index + 1)); } catch (CharacterCodingException e) { throw new IllegalArgumentException(e); } } }