org.apache.hadoop.hive.metastore.utils.JavaUtils Maven / Gradle / Ivy

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/*
 * 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.hadoop.hive.metastore.utils;

import org.apache.hadoop.hive.metastore.api.MetaException;
import com.facebook.presto.hive.$internal.org.slf4j.Logger;
import com.facebook.presto.hive.$internal.org.slf4j.LoggerFactory;

import java.lang.reflect.Constructor;
import java.net.InetAddress;
import java.net.UnknownHostException;

public class JavaUtils {
  public static final Logger LOG = LoggerFactory.getLogger(JavaUtils.class);

  /**
   * Standard way of getting classloader in Hive code (outside of Hadoop).
   *
   * Uses the context loader to get access to classpaths to auxiliary and jars
   * added with 'add jar' command. Falls back to current classloader.
   *
   * In Hadoop-related code, we use Configuration.getClassLoader().
   * @return the class loader
   */
  public static ClassLoader getClassLoader() {
    ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
    if (classLoader == null) {
      classLoader = JavaUtils.class.getClassLoader();
    }
    return classLoader;
  }

  @SuppressWarnings(value = "unchecked")
  public static  Class getClass(String className, Class clazz)
      throws MetaException {
    try {
      return (Class) Class.forName(className, true, getClassLoader());
    } catch (ClassNotFoundException e) {
      throw new MetaException(className + " class not found");
    }
  }

  /**
   * Create an object of the given class.
   * @param theClass
   * @param parameterTypes
   *          an array of parameterTypes for the constructor
   * @param initargs
   *          the list of arguments for the constructor
   */
  public static  T newInstance(Class theClass, Class[] parameterTypes,
                                  Object[] initargs) {
    // Perform some sanity checks on the arguments.
    if (parameterTypes.length != initargs.length) {
      throw new IllegalArgumentException(
          "Number of constructor parameter types doesn't match number of arguments");
    }
    for (int i = 0; i < parameterTypes.length; i++) {
      Class clazz = parameterTypes[i];
      if (initargs[i] != null && !(clazz.isInstance(initargs[i]))) {
        throw new IllegalArgumentException("Object : " + initargs[i]
            + " is not an instance of " + clazz);
      }
    }

    try {
      Constructor meth = theClass.getDeclaredConstructor(parameterTypes);
      meth.setAccessible(true);
      return meth.newInstance(initargs);
    } catch (Exception e) {
      throw new RuntimeException("Unable to instantiate " + theClass.getName(), e);
    }
  }

  /**
   * Create an object of the given class using a no-args constructor
   * @param theClass class to return new object of
   * @param  the type of the class to be returned
   * @return an object of the requested type
   */
  public static  T newInstance(Class theClass) {
    try {
      return theClass.newInstance();
    } catch (InstantiationException|IllegalAccessException e) {
      throw new RuntimeException("Unable to instantiate " + theClass.getName(), e);
    }
  }

  /**
   * @return name of current host
   */
  public static String hostname() {
    try {
      return InetAddress.getLocalHost().getHostName();
    } catch (UnknownHostException e) {
      LOG.error("Unable to resolve my host name " + e.getMessage());
      throw new RuntimeException(e);
    }
  }

  /**
   * Utility method for ACID to normalize logging info.  Matches
   * org.apache.hadoop.hive.metastore.api.LockRequest#toString
   */
  public static String lockIdToString(long extLockId) {
    return "lockid:" + extLockId;
  }
  /**
   * Utility method for ACID to normalize logging info.  Matches
   * org.apache.hadoop.hive.metastore.api.LockResponse#toString
   */
  public static String txnIdToString(long txnId) {
    return "txnid:" + txnId;
  }
}