ClassPathModifyingSqoopShim.java

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 *
 * Pentaho Big Data
 *
 * Copyright (C) 2002-2013 by Pentaho : http://www.pentaho.com
 *
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 *
 * 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
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 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
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package org.pentaho.hadoop.shim.common;

import org.apache.sqoop.Sqoop;
import org.pentaho.hadoop.shim.HadoopConfigurationClassLoader;
import org.pentaho.hadoop.shim.api.Configuration;

import java.util.concurrent.Callable;

/**
 * Sqoop shim to handle working around Sqoop's ConfigurationManager and how it builds up the class path when compiling
 * temporary files.
 * <p/>
 * <p> This applies to any version of Hadoop that bundles classes in separate jars instead of the conglomerate "core"
 * jar. </p>
 */
public class ClassPathModifyingSqoopShim extends CommonSqoopShim {
  protected static final String PROPERTY_JAVA_CLASS_PATH = "java.class.path";

  /**
   * Run a given {@link java.util.concurrent.Callable} within a code block that sets the {@code "java.class.path"} property to the path
   * defined for the {@link org.pentaho.hadoop.shim.HadoopConfigurationClassLoader} used to load this class, if it was used. If not, this is the
   * same as calling {@code callable.call()}.
   *
   * @param callable Callable to execute with a modified class path set.
   * @return
   */
  public int runWithModifiedClassPathProperty( Callable<Integer> callable ) {
    /**
     * WARNING: This is non-thread safe. This is only to work around the
     * deficiencies of the Sqoop CompilationManager (as of 1.4.1) as it will
     * only look for the Hadoop "core" jar. For CDH4 the necessary classes are contained within a
     * "common" jar.
     */
    String newClassPath = getClassPathString();
    String originalClassPath = System.getProperty( PROPERTY_JAVA_CLASS_PATH );
    if ( newClassPath != null ) {
      System.setProperty( PROPERTY_JAVA_CLASS_PATH, newClassPath );
    }
    try {
      Integer returnVal = callable.call();
      return returnVal == null ? Integer.MIN_VALUE : returnVal.intValue();
    } catch ( Exception ex ) {
      throw new RuntimeException( ex );
    } finally {
      if ( originalClassPath != null ) {
        System.setProperty( PROPERTY_JAVA_CLASS_PATH, originalClassPath );
      }
    }
  }

  @Override
  public int runTool( final String[] args, final Configuration c ) {
    return runWithModifiedClassPathProperty( new Callable<Integer>() {
      @Override
      public Integer call() throws Exception {
        ClassLoader cl = Thread.currentThread().getContextClassLoader();
        Thread.currentThread().setContextClassLoader( getClass().getClassLoader() );
        try {
          return Sqoop.runTool( args, ShimUtils.asConfiguration( c ) );
        } finally {
          Thread.currentThread().setContextClassLoader( cl );
        }
      }
    } );
  }

  /**
   * @return the class path to set for each run of {@link #runWithModifiedClassPathProperty(java.util.concurrent.Callable)}.
   */
  protected String getClassPathString() {
    ClassLoader cl = getClass().getClassLoader();
    if ( HadoopConfigurationClassLoader.class.isAssignableFrom( cl.getClass() ) ) {
      HadoopConfigurationClassLoader hccl = (HadoopConfigurationClassLoader) cl;
      return hccl.generateClassPathString();
    }
    return null;
  }
}