/*
 * 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.sentry.provider.common;

import java.io.IOException;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.security.Groups;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class HadoopGroupMappingService implements GroupMappingService {

  private static final Logger LOGGER = LoggerFactory
      .getLogger(HadoopGroupMappingService.class);
  private final Groups groups;

  public HadoopGroupMappingService(Groups groups) {
    this.groups = groups;
  }

  @Override
  public Set<String> getGroups(String user) {
    try {
      return new HashSet<String>(groups.getGroups(user));
    } catch (IOException e) {
      LOGGER.warn("Unable to obtain groups for " + user, e);
    }
    return Collections.emptySet();
  }
}

/*
 * 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.sentry.provider.common;

import java.io.IOException;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.security.Groups;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class HadoopGroupMappingService implements GroupMappingService {

  private static final Logger LOGGER = LoggerFactory
      .getLogger(HadoopGroupMappingService.class);
  private final Groups groups;

  public HadoopGroupMappingService(Groups groups) {
    this.groups = groups;
  }

  public HadoopGroupMappingService(Configuration conf, String resource) {
    this(Groups.getUserToGroupsMappingService(conf));
  }

  @Override
  public Set<String> getGroups(String user) {
    try {
      return new HashSet<String>(groups.getGroups(user));
    } catch (IOException e) {
      LOGGER.warn("Unable to obtain groups for " + user, e);
    }
    return Collections.emptySet();
  }
}

Add a new constructor to HadoopGroupMappingService (GuoquanShen, reviewed by Dapeng Sun)