co.cask.cdap.internal.app.runtime.batch.WrapperUtil.java Source code

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Here is the source code for co.cask.cdap.internal.app.runtime.batch.WrapperUtil.java

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/*
 * Copyright  2016 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.internal.app.runtime.batch;

import co.cask.cdap.api.ProgramLifecycle;
import co.cask.cdap.common.lang.ClassLoaders;
import com.google.common.base.Preconditions;
import com.google.common.base.Throwables;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.util.ReflectionUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Utility class that helps with creating and initializing objects from, based upon an attribute in
 * a {@link Configuration}.
 */
public final class WrapperUtil {
    private static final Logger LOG = LoggerFactory.getLogger(WrapperUtil.class);

    private WrapperUtil() {
    }

    // instantiates and initializes (if its a ProgramLifeCycle) the class specified by the attribute
    static <T> T createDelegate(Configuration conf, String attrClass) {
        String delegateClassName = conf.get(attrClass);
        Class<?> delegateClass = conf.getClassByNameOrNull(delegateClassName);
        Preconditions.checkNotNull(delegateClass, "Class could not be found: ", delegateClassName);
        T delegate = (T) ReflectionUtils.newInstance(delegateClass, conf);

        if (!(delegate instanceof ProgramLifecycle)) {
            return delegate;
        }

        MapReduceClassLoader classLoader = MapReduceClassLoader.getFromConfiguration(conf);
        BasicMapReduceTaskContext basicMapReduceContext = classLoader.getTaskContextProvider().get(conf);
        ClassLoader programClassLoader = classLoader.getProgramClassLoader();

        ClassLoader oldClassLoader = ClassLoaders.setContextClassLoader(programClassLoader);
        try {
            ProgramLifecycle programLifecycle = (ProgramLifecycle) delegate;
            programLifecycle.initialize(new MapReduceLifecycleContext(basicMapReduceContext));

            // register it so that its destroy method can get called when the BasicMapReduceTaskContext is closed
            basicMapReduceContext.registerProgramLifecycle(programLifecycle);
            return delegate;
        } catch (Exception e) {
            LOG.error("Failed to initialize delegate with {}", basicMapReduceContext, e);
            throw Throwables.propagate(e);
        } finally {
            ClassLoaders.setContextClassLoader(oldClassLoader);
        }
    }

    // copies the value from src key to destination key
    // return true if the src key had a corresponding value
    static boolean setIfDefined(Job job, String srcKey, String destinationKey) {
        // NOTE: we don't use job.getXClass or conf.getClass as we don't need to load user class here
        Configuration conf = job.getConfiguration();
        String srcVal = conf.get(srcKey);
        if (srcVal != null) {
            conf.set(destinationKey, srcVal);
            return true;
        }
        return false;
    }
}