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. */ package org.apache.nutch.indexer; import org.apache.hadoop.conf.Configuration; public class NutchIndexWriterFactory { @SuppressWarnings("unchecked") public static NutchIndexWriter[] getNutchIndexWriters(Configuration conf) { final String[] classes = conf.getStrings("indexer.writer.classes"); final NutchIndexWriter[] writers = new NutchIndexWriter[classes.length]; for (int i = 0; i < classes.length; i++) { final String clazz = classes[i]; try { final Class<NutchIndexWriter> implClass = (Class<NutchIndexWriter>) Class.forName(clazz); writers[i] = implClass.newInstance(); } catch (final Exception e) { throw new RuntimeException("Couldn't create " + clazz, e); } } return writers; } public static void addClassToConf(Configuration conf, Class<? extends NutchIndexWriter> clazz) { final String classes = conf.get("indexer.writer.classes"); final String newClass = clazz.getName(); if (classes == null) { conf.set("indexer.writer.classes", newClass); } else { conf.set("indexer.writer.classes", classes + "," + newClass); } } }