/**
* 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.falcon.util;
import org.apache.falcon.FalconException;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
/**
* Helper methods for class instantiation through reflection.
*/
public final class ReflectionUtils {
private ReflectionUtils() {}
public static <T> T getInstance(String classKey) throws FalconException {
return ReflectionUtils.<T>getInstanceByClassName(StartupProperties.get().getProperty(classKey));
}
public static <T> T getInstance(String classKey, Class<?> argCls, Object arg) throws FalconException {
return ReflectionUtils.<T>getInstanceByClassName(StartupProperties.get().getProperty(classKey), argCls, arg);
}
@SuppressWarnings("unchecked")
public static <T> T getInstanceByClassName(String clazzName) throws FalconException {
try {
Class<T> clazz = (Class<T>) ReflectionUtils.class.getClassLoader().loadClass(clazzName);
try {
return clazz.newInstance();
} catch (IllegalAccessException e) {
Method method = clazz.getMethod("get");
return (T) method.invoke(null);
}
} catch (Exception e) {
throw new FalconException("Unable to get instance for " + clazzName, e);
}
}
/**
* Invokes constructor with one argument.
* @param clazzName - classname
* @param argCls - Class of the argument
* @param arg - constructor argument
* @param <T> - instance type
* @return Class instance
* @throws FalconException
*/
@SuppressWarnings("unchecked")
public static <T> T getInstanceByClassName(String clazzName, Class<?> argCls, Object arg) throws
FalconException {
try {
Class<T> clazz = (Class<T>) ReflectionUtils.class.getClassLoader().loadClass(clazzName);
Constructor<T> constructor = clazz.getConstructor(argCls);
return constructor.newInstance(arg);
} catch (Exception e) {
throw new FalconException("Unable to get instance for " + clazzName, e);
}
}
}