org.apache.hadoop.hbase.util.ReflectionUtils 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.hbase.util;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;

import org.apache.hadoop.hbase.classification.InterfaceAudience;

@InterfaceAudience.Private
public class ReflectionUtils {
  @SuppressWarnings("unchecked")
  public static  T instantiateWithCustomCtor(String className,
      Class[] ctorArgTypes, Object[] ctorArgs) {
    try {
      Class resultType = (Class) Class.forName(className);
      Constructor ctor = resultType.getDeclaredConstructor(ctorArgTypes);
      return instantiate(className, ctor, ctorArgs);
    } catch (ClassNotFoundException e) {
      throw new UnsupportedOperationException(
          "Unable to find " + className, e);
    } catch (NoSuchMethodException e) {
      throw new UnsupportedOperationException(
          "Unable to find suitable constructor for class " + className, e);
    }
  }

  private static  T instantiate(final String className, Constructor ctor, Object[] ctorArgs) {
    try {
      return ctor.newInstance(ctorArgs);
    } catch (IllegalAccessException e) {
      throw new UnsupportedOperationException(
          "Unable to access specified class " + className, e);
    } catch (InstantiationException e) {
      throw new UnsupportedOperationException(
          "Unable to instantiate specified class " + className, e);
    } catch (InvocationTargetException e) {
      throw new UnsupportedOperationException(
          "Constructor threw an exception for " + className, e);
    }
  }

  @SuppressWarnings("unchecked")
  public static  T newInstance(Class type, Object... params) {
    return instantiate(type.getName(), findConstructor(type, params), params);
  }

  @SuppressWarnings("unchecked")
  public static  Constructor findConstructor(Class type, Object... paramTypes) {
    Constructor[] constructors = (Constructor[])type.getConstructors();
    for (Constructor ctor : constructors) {
      Class[] ctorParamTypes = ctor.getParameterTypes();
      if (ctorParamTypes.length != paramTypes.length) {
        continue;
      }

      boolean match = true;
      for (int i = 0; i < ctorParamTypes.length && match; ++i) {
        Class paramType = paramTypes[i].getClass();
        match = (!ctorParamTypes[i].isPrimitive()) ? ctorParamTypes[i].isAssignableFrom(paramType) :
                  ((int.class.equals(ctorParamTypes[i]) && Integer.class.equals(paramType)) ||
                   (long.class.equals(ctorParamTypes[i]) && Long.class.equals(paramType)) ||
                   (char.class.equals(ctorParamTypes[i]) && Character.class.equals(paramType)) ||
                   (short.class.equals(ctorParamTypes[i]) && Short.class.equals(paramType)) ||
                   (boolean.class.equals(ctorParamTypes[i]) && Boolean.class.equals(paramType)) ||
                   (byte.class.equals(ctorParamTypes[i]) && Byte.class.equals(paramType)));
      }

      if (match) {
        return ctor;
      }
    }
    throw new UnsupportedOperationException(
      "Unable to find suitable constructor for class " + type.getName());
  }
}