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.mahout.cf.taste.hadoop.item; import java.io.IOException; import java.io.InputStream; import java.util.HashMap; import java.util.Map; import java.util.regex.Pattern; import com.google.common.collect.Maps; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.Path; import org.apache.mahout.cf.taste.impl.common.FastIDSet; import org.apache.mahout.common.HadoopUtil; import org.apache.mahout.common.iterator.FileLineIterable; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import com.google.common.io.Closeables; /** * Reads user ids and item ids from files specified in usersFile, itemsFile or userItemFile options in item-based * recommender. Composes a list of users and a list of items which can be used by * {@link org.apache.mahout.cf.taste.hadoop.item.UserVectorSplitterMapper} and * {@link org.apache.mahout.cf.taste.hadoop.item.AggregateAndRecommendReducer}. */ public class IDReader { static final String USER_ITEM_FILE = "userItemFile"; private static final Logger log = LoggerFactory.getLogger(IDReader.class); private static final Pattern SEPARATOR = Pattern.compile("[\t,]"); private Configuration conf; private String usersFile; private String itemsFile; private String userItemFile; private FastIDSet userIds; private FastIDSet itemIds; private FastIDSet emptySet; /* Key - user id, value - a set of item ids to include into recommendations for this user */ private Map<Long, FastIDSet> userItemFilter; /** * Creates a new IDReader * * @param conf Job configuration */ public IDReader(Configuration conf) { this.conf = conf; emptySet = new FastIDSet(); usersFile = conf.get(UserVectorSplitterMapper.USERS_FILE); itemsFile = conf.get(AggregateAndRecommendReducer.ITEMS_FILE); userItemFile = conf.get(USER_ITEM_FILE); } /** * Reads user ids and item ids from files specified in a job configuration * * @throws IOException if an error occurs during file read operation * * @throws IllegalStateException if userItemFile option is specified together with usersFile or itemsFile */ public void readIDs() throws IOException, IllegalStateException { if (isUserItemFileSpecified()) { readUserItemFilterIfNeeded(); } if (isUsersFileSpecified() || isUserItemFilterSpecified()) { readUserIds(); } if (isItemsFileSpecified() || isUserItemFilterSpecified()) { readItemIds(); } } /** * Gets a collection of items which should be recommended for a user * * @param userId ID of a user we are interested in * @return if a userItemFile option is specified, and that file contains at least one item ID for the user, * then this method returns a {@link FastIDSet} object populated with item IDs. Otherwise, this * method returns an empty set. */ public FastIDSet getItemsToRecommendForUser(Long userId) { if (isUserItemFilterSpecified() && userItemFilter.containsKey(userId)) { return userItemFilter.get(userId); } else { return emptySet; } } private void readUserIds() throws IOException, IllegalStateException { if (isUsersFileSpecified() && !isUserItemFileSpecified()) { userIds = readIDList(usersFile); } else if (isUserItemFileSpecified() && !isUsersFileSpecified()) { readUserItemFilterIfNeeded(); userIds = extractAllUserIdsFromUserItemFilter(userItemFilter); } else if (!isUsersFileSpecified() && !isUserItemFileSpecified()) { throw new IllegalStateException("Neither usersFile nor userItemFile options are specified"); } else { throw new IllegalStateException("usersFile and userItemFile options cannot be used simultaneously"); } } private void readItemIds() throws IOException, IllegalStateException { if (isItemsFileSpecified() && !isUserItemFileSpecified()) { itemIds = readIDList(itemsFile); } else if (isUserItemFileSpecified() && !isItemsFileSpecified()) { readUserItemFilterIfNeeded(); itemIds = extractAllItemIdsFromUserItemFilter(userItemFilter); } else if (!isItemsFileSpecified() && !isUserItemFileSpecified()) { throw new IllegalStateException("Neither itemsFile nor userItemFile options are specified"); } else { throw new IllegalStateException( "itemsFile and userItemFile options cannot be specified simultaneously"); } } private void readUserItemFilterIfNeeded() throws IOException { if (!isUserItemFilterSpecified() && isUserItemFileSpecified()) { userItemFilter = readUserItemFilter(userItemFile); } } private Map<Long, FastIDSet> readUserItemFilter(String pathString) throws IOException { Map<Long, FastIDSet> result = Maps.newHashMap(); InputStream in = openFile(pathString); try { for (String line : new FileLineIterable(in)) { try { String[] tokens = SEPARATOR.split(line.toString()); Long userId = Long.parseLong(tokens[0]); Long itemId = Long.parseLong(tokens[1]); addUserAndItemIdToUserItemFilter(result, userId, itemId); } catch (NumberFormatException nfe) { log.warn("userItemFile line ignored: {}", line); } } } finally { Closeables.close(in, true); } return result; } void addUserAndItemIdToUserItemFilter(Map<Long, FastIDSet> filter, Long userId, Long itemId) { FastIDSet itemIds; if (filter.containsKey(userId)) { itemIds = filter.get(userId); } else { itemIds = new FastIDSet(); filter.put(userId, itemIds); } itemIds.add(itemId); } static FastIDSet extractAllUserIdsFromUserItemFilter(Map<Long, FastIDSet> filter) { FastIDSet result = new FastIDSet(); for (Long userId : filter.keySet()) { result.add(userId); } return result; } private FastIDSet extractAllItemIdsFromUserItemFilter(Map<Long, FastIDSet> filter) { FastIDSet result = new FastIDSet(); for (FastIDSet itemIds : filter.values()) { result.addAll(itemIds); } return result; } private FastIDSet readIDList(String pathString) throws IOException { FastIDSet result = null; if (pathString != null) { result = new FastIDSet(); InputStream in = openFile(pathString); try { for (String line : new FileLineIterable(in)) { try { result.add(Long.parseLong(line)); } catch (NumberFormatException nfe) { log.warn("line ignored: {}", line); } } } finally { Closeables.close(in, true); } } return result; } private InputStream openFile(String pathString) throws IOException { return HadoopUtil.openStream(new Path(pathString), conf); } public boolean isUsersFileSpecified() { return usersFile != null; } public boolean isItemsFileSpecified() { return itemsFile != null; } public boolean isUserItemFileSpecified() { return userItemFile != null; } public boolean isUserItemFilterSpecified() { return userItemFilter != null; } public FastIDSet getUserIds() { return userIds; } public FastIDSet getItemIds() { return itemIds; } }