| /** |
| * 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.hcatalog.data.transfer; |
| |
| import java.util.Iterator; |
| import java.util.Map; |
| import java.util.Map.Entry; |
| |
| import org.apache.hadoop.conf.Configuration; |
| import org.apache.hcatalog.common.HCatException; |
| import org.apache.hcatalog.data.HCatRecord; |
| import org.apache.hcatalog.data.transfer.state.StateProvider; |
| |
| /** |
| * This abstract class is internal to HCatalog and abstracts away the notion of |
| * underlying system from which reads will be done. |
| */ |
| |
| public abstract class HCatReader { |
| |
| /** |
| * This should be called at master node to obtain {@link ReaderContext} which |
| * then should be serialized and sent to slave nodes. |
| * |
| * @return {@link ReaderContext} |
| * @throws HCatException |
| */ |
| public abstract ReaderContext prepareRead() throws HCatException; |
| |
| /** |
| * This should be called at slave nodes to read {@link HCatRecord}s |
| * |
| * @return {@link Iterator} of {@link HCatRecord} |
| * @throws HCatException |
| */ |
| public abstract Iterator<HCatRecord> read() throws HCatException; |
| |
| /** |
| * This constructor will be invoked by {@link DataTransferFactory} at master |
| * node. Don't use this constructor. Instead, use {@link DataTransferFactory} |
| * |
| * @param re |
| * @param config |
| */ |
| protected HCatReader(final ReadEntity re, final Map<String, String> config) { |
| this(config); |
| this.re = re; |
| } |
| |
| /** |
| * This constructor will be invoked by {@link DataTransferFactory} at slave |
| * nodes. Don't use this constructor. Instead, use {@link DataTransferFactory} |
| * |
| * @param config |
| * @param sp |
| */ |
| |
| protected HCatReader(final Configuration config, StateProvider sp) { |
| this.conf = config; |
| this.sp = sp; |
| } |
| |
| protected ReadEntity re; // This will be null at slaves. |
| protected Configuration conf; |
| protected ReaderContext info; |
| protected StateProvider sp; // This will be null at master. |
| |
| private HCatReader(final Map<String, String> config) { |
| Configuration conf = new Configuration(); |
| if (null != config) { |
| for (Entry<String, String> kv : config.entrySet()) { |
| conf.set(kv.getKey(), kv.getValue()); |
| } |
| } |
| this.conf = conf; |
| } |
| |
| public Configuration getConf() { |
| if (null == conf) { |
| throw new IllegalStateException( |
| "HCatReader is not constructed correctly."); |
| } |
| return conf; |
| } |
| } |