org.apache.hive.common.util.ReflectionUtil Maven / Gradle / Ivy
/**
* 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.hive.common.util;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.util.concurrent.TimeUnit;
import org.apache.hadoop.conf.Configurable;
import org.apache.hadoop.conf.Configuration;
import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;
/**
* Same as Hadoop ReflectionUtils, but (1) does not leak classloaders (or shouldn't anyway, we
* rely on Guava cache, and could fix it otherwise); (2) does not have a hidden epic lock.
*/
public class ReflectionUtil {
// TODO: expireAfterAccess locks cache segments on put and expired get. It doesn't look too bad,
// but if we find some perf issues it might be a good idea to remove this - we are probably
// not caching that many constructors.
// Note that weakKeys causes "==" to be used for key compare; this will only work
// for classes in the same classloader. Should be ok in this case.
private static final Cache, Constructor> CONSTRUCTOR_CACHE =
CacheBuilder.newBuilder().expireAfterAccess(15, TimeUnit.MINUTES)
.concurrencyLevel(64)
.weakKeys().weakValues().build();
private static final Class[] EMPTY_ARRAY = new Class[] {};
private static final Class jobConfClass, jobConfigurableClass;
private static final Method configureMethod;
static {
Class jobConfClassLocal, jobConfigurableClassLocal;
Method configureMethodLocal;
try {
jobConfClassLocal = Class.forName("org.apache.hadoop.mapred.JobConf");
jobConfigurableClassLocal = Class.forName("org.apache.hadoop.mapred.JobConfigurable");
configureMethodLocal = jobConfigurableClassLocal.getMethod("configure", jobConfClassLocal);
} catch (Throwable t) {
// Meh.
jobConfClassLocal = jobConfigurableClassLocal = null;
configureMethodLocal = null;
}
jobConfClass = jobConfClassLocal;
jobConfigurableClass = jobConfigurableClassLocal;
configureMethod = configureMethodLocal;
}
/**
* Create an object for the given class and initialize it from conf
* @param theClass class of which an object is created
* @param conf Configuration
* @return a new object
*/
@SuppressWarnings("unchecked")
public static T newInstance(Class theClass, Configuration conf) {
T result;
try {
Constructor ctor = CONSTRUCTOR_CACHE.getIfPresent(theClass);
if (ctor == null) {
ctor = theClass.getDeclaredConstructor(EMPTY_ARRAY);
ctor.setAccessible(true);
CONSTRUCTOR_CACHE.put(theClass, ctor);
}
result = (T)ctor.newInstance();
} catch (Exception e) {
throw new RuntimeException(e);
}
setConf(result, conf);
return result;
}
/**
* Check and set 'configuration' if necessary.
*
* @param theObject object for which to set configuration
* @param conf Configuration
*/
public static void setConf(Object theObject, Configuration conf) {
if (conf != null) {
if (theObject instanceof Configurable) {
((Configurable) theObject).setConf(conf);
}
setJobConf(theObject, conf);
}
}
private static void setJobConf(Object theObject, Configuration conf) {
if (configureMethod == null) return;
try {
if (jobConfClass.isAssignableFrom(conf.getClass()) &&
jobConfigurableClass.isAssignableFrom(theObject.getClass())) {
configureMethod.invoke(theObject, conf);
}
} catch (Exception e) {
throw new RuntimeException("Error in configuring object", e);
}
}
}