| /** |
| * 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 com.datatorrent.lib.db; |
| |
| import java.util.ArrayList; |
| import java.util.HashMap; |
| import java.util.Iterator; |
| import java.util.List; |
| import java.util.Map; |
| |
| /** |
| * This is the base implementation of an input operator which consumes data from a key value store. |
| * Subclasses should implement the method which converts key value pairs into tuples. |
| * <p> |
| * The default behavior is to get all the values using the keys from the store for each window. Subclasses are free to override this behavior. |
| * </p> |
| * @displayName Abstract Key Value Store Input |
| * @category Input |
| * @tags key value |
| * |
| * @param <T> The tuple type. |
| * @param <S> The store type. |
| * @since 0.9.3 |
| */ |
| @org.apache.hadoop.classification.InterfaceStability.Evolving |
| public abstract class AbstractKeyValueStoreInputOperator<T, S extends KeyValueStore> extends AbstractStoreInputOperator<T, S> |
| { |
| protected List<Object> keys = new ArrayList<Object>(); |
| |
| /** |
| * Adds the key to the list of keys to be fetched for each window |
| * |
| * @param key a key. |
| */ |
| public void addKey(Object key) |
| { |
| keys.add(key); |
| } |
| |
| @Override |
| public void emitTuples() |
| { |
| List<Object> allValues = store.getAll(keys); |
| Map<Object, Object> m = new HashMap<Object, Object>(); |
| Iterator<Object> keyIterator = keys.iterator(); |
| Iterator<Object> valueIterator = allValues.iterator(); |
| while (keyIterator.hasNext() && valueIterator.hasNext()) { |
| m.put(keyIterator.next(), valueIterator.next()); |
| } |
| outputPort.emit(convertToTuple(m)); |
| } |
| |
| /** |
| * Implementations should provide the way of converting from a map of key value pairs from the store to a tuple. |
| * |
| * @param o map of keys and values. |
| * @return tuple. |
| */ |
| public abstract T convertToTuple(Map<Object, Object> o); |
| |
| } |