| /* |
| * 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.samza.util; |
| |
| import java.lang.reflect.Constructor; |
| import java.util.stream.IntStream; |
| import org.apache.commons.lang3.Validate; |
| import org.apache.samza.SamzaException; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| |
| /** |
| * Helper methods for reflection usage. |
| */ |
| public class ReflectionUtil { |
| private static final Logger LOG = LoggerFactory.getLogger(ReflectionUtil.class); |
| |
| private ReflectionUtil() { |
| } |
| |
| /** |
| * Create an instance of the specified class with the empty constructor. |
| * |
| * @param <T> type of the object to return |
| * @param className name of the class |
| * @param clazz type of object to return |
| * @return instance of the class |
| * @throws SamzaException if an exception was thrown while trying to create the class |
| */ |
| public static <T> T getObj(String className, Class<T> clazz) { |
| return doGetObjWithArgs(className, clazz); |
| } |
| |
| /** |
| * Create an instance of the specified class with constructor matching the arguments. Make sure that the types passed |
| * using {@link ConstructorArgument} match the compile-time types of the arguments of the constructor that should be |
| * used. |
| * |
| * @param <T> type of the object to return |
| * @param className name of the class |
| * @param clazz type of object to return |
| * @param args arguments with types for finding and calling desired constructor to create an instance of className |
| * @return instance of the class |
| * @throws SamzaException if an exception was thrown while trying to create the class |
| */ |
| public static <T> T getObjWithArgs(String className, Class<T> clazz, ConstructorArgument<?>... args) { |
| return doGetObjWithArgs(className, clazz, args); |
| } |
| |
| /** |
| * Use this to create arguments for when calling |
| * {@link #doGetObjWithArgs(String, Class, ConstructorArgument[])} |
| */ |
| public static <T> ConstructorArgument<T> constructorArgument(T value, Class<T> clazz) { |
| return new ConstructorArgument<>(value, clazz); |
| } |
| |
| /** |
| * Create an instance of the specified class with constructor matching the argument array. If there are no args, then |
| * this will use the empty constructor. Make sure that the types passed using {@link ConstructorArgument} match the |
| * compile-time types of the arguments of the constructor that should be used. |
| * |
| * @param <T> type of the object to return |
| * @param className name of the class |
| * @param clazz type of object to return |
| * @param args arguments with types for finding and calling desired constructor to create an instance of className |
| * @return instance of the class |
| * @throws SamzaException if an exception was thrown while trying to create the class |
| */ |
| private static <T> T doGetObjWithArgs(String className, Class<T> clazz, ConstructorArgument<?>... args) { |
| Validate.notNull(className, "Null class name"); |
| |
| try { |
| //noinspection unchecked |
| Class<T> classObj = (Class<T>) Class.forName(className); |
| if (args.length == 0) { |
| return classObj.newInstance(); |
| } else { |
| // can't just use getClass on argument values since runtime types might not exactly match constructor signatures |
| Class<?>[] argClasses = new Class<?>[args.length]; |
| Object[] argValues = new Object[args.length]; |
| IntStream.range(0, args.length).forEach(i -> { |
| ConstructorArgument<?> constructorArgument = args[i]; |
| argClasses[i] = constructorArgument.getClazz(); |
| argValues[i] = constructorArgument.getValue(); |
| }); |
| Constructor<T> constructor = classObj.getDeclaredConstructor(argClasses); |
| return constructor.newInstance(argValues); |
| } |
| } catch (Exception e) { |
| String errorMessage = String.format("Unable to create instance for class: %s", className); |
| LOG.error(errorMessage, e); |
| throw new SamzaException(errorMessage, e); |
| } |
| } |
| |
| /** |
| * This is public because the compiler complains when using a non-visible modifier with varargs. |
| * Use {@link #constructorArgument(Object, Class)} to build an instance of this. |
| */ |
| public static class ConstructorArgument<T> { |
| private final T value; |
| private final Class<T> clazz; |
| |
| private ConstructorArgument(T value, Class<T> clazz) { |
| this.value = value; |
| this.clazz = clazz; |
| } |
| |
| private T getValue() { |
| return value; |
| } |
| |
| private Class<T> getClazz() { |
| return clazz; |
| } |
| } |
| } |