co.cask.cdap.security.impersonation.ImpersonationUtils.java Source code

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Here is the source code for co.cask.cdap.security.impersonation.ImpersonationUtils.java

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/*
 * Copyright  2016-2017 Cask Data, Inc.
 *
 * Licensed 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 co.cask.cdap.security.impersonation;

import com.google.common.base.Throwables;
import org.apache.hadoop.security.UserGroupInformation;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.lang.reflect.UndeclaredThrowableException;
import java.security.PrivilegedExceptionAction;
import java.util.concurrent.Callable;

/**
 * Utility functions for impersonation.
 */
public final class ImpersonationUtils {

    private static final Logger LOG = LoggerFactory.getLogger(ImpersonationUtils.class);

    private ImpersonationUtils() {
    }

    /**
     * Helper function, to unwrap any exceptions that were wrapped
     * by {@link UserGroupInformation#doAs(PrivilegedExceptionAction)}
     */
    public static <T> T doAs(UserGroupInformation ugi, final Callable<T> callable) throws Exception {
        try {
            return ugi.doAs(new PrivilegedExceptionAction<T>() {
                @Override
                public T run() throws Exception {
                    return callable.call();
                }
            });
        } catch (UndeclaredThrowableException e) {
            // UserGroupInformation#doAs will wrap any checked exceptions, so unwrap and rethrow here
            Throwable wrappedException = e.getUndeclaredThrowable();
            Throwables.propagateIfPossible(wrappedException);

            if (wrappedException instanceof Exception) {
                throw (Exception) wrappedException;
            }
            // since PrivilegedExceptionAction#run can only throw Exception (besides runtime exception),
            // this should never happen
            LOG.warn("Unexpected exception while executing callable as {}.", ugi.getUserName(), wrappedException);
            throw Throwables.propagate(wrappedException);
        }
    }
}