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.oozie.service; import java.io.IOException; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.ConcurrentMap; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.security.UserGroupInformation; import org.apache.oozie.util.XLog; public class UserGroupInformationService implements Service { private ConcurrentMap<String, UserGroupInformation> cache = new ConcurrentHashMap<String, UserGroupInformation>(); @Override public void init(Services services) throws ServiceException { } @Override public void destroy() { for (UserGroupInformation ugi : cache.values()) { try { FileSystem.closeAllForUGI(ugi); } catch (IOException ioe) { XLog.getLog(this.getClass()) .warn("Exception occurred while closing filesystems for " + ugi.getUserName(), ioe); } } cache.clear(); } @Override public Class<? extends Service> getInterface() { return UserGroupInformationService.class; } public UserGroupInformation getProxyUser(String user) throws IOException { cache.putIfAbsent(user, UserGroupInformation.createProxyUser(user, UserGroupInformation.getLoginUser())); return cache.get(user); } }