spring-batch AbstractMethodInvokingDelegator 源码

  • 2022-08-16
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spring-batch AbstractMethodInvokingDelegator 代码

文件路径:/spring-batch-infrastructure/src/main/java/org/springframework/batch/item/adapter/AbstractMethodInvokingDelegator.java

/*
 * Copyright 2006-2018 the original author or authors.
 *
 * Licensed 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
 *
 *      https://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.springframework.batch.item.adapter;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import org.springframework.beans.factory.InitializingBean;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.MethodInvoker;

/**
 * Superclass for delegating classes which dynamically call a custom method of injected
 * object. Provides convenient API for dynamic method invocation shielding subclasses from
 * low-level details and exception handling.
 *
 * {@link Exception}s thrown by a successfully invoked delegate method are re-thrown
 * without wrapping. In case the delegate method throws a {@link Throwable} that doesn't
 * subclass {@link Exception} it will be wrapped by
 * {@link InvocationTargetThrowableWrapper}.
 *
 * @author Robert Kasanicky
 * @author Mahmoud Ben Hassine
 */
public abstract class AbstractMethodInvokingDelegator<T> implements InitializingBean {

	private Object targetObject;

	private String targetMethod;

	private Object[] arguments;

	/**
	 * Invoker the target method with arguments set by {@link #setArguments(Object[])}.
	 * @return object returned by invoked method
	 * @throws Exception exception thrown when executing the delegate method.
	 */
	protected T invokeDelegateMethod() throws Exception {
		MethodInvoker invoker = createMethodInvoker(targetObject, targetMethod);
		invoker.setArguments(arguments);
		return doInvoke(invoker);
	}

	/**
	 * Invokes the target method with given argument.
	 * @param object argument for the target method
	 * @return object returned by target method
	 * @throws Exception exception thrown when executing the delegate method.
	 */
	protected T invokeDelegateMethodWithArgument(Object object) throws Exception {
		MethodInvoker invoker = createMethodInvoker(targetObject, targetMethod);
		invoker.setArguments(new Object[] { object });
		return doInvoke(invoker);
	}

	/**
	 * Invokes the target method with given arguments.
	 * @param args arguments for the invoked method
	 * @return object returned by invoked method
	 * @throws Exception exception thrown when executing the delegate method.
	 */
	protected T invokeDelegateMethodWithArguments(Object[] args) throws Exception {
		MethodInvoker invoker = createMethodInvoker(targetObject, targetMethod);
		invoker.setArguments(args);
		return doInvoke(invoker);
	}

	/**
	 * Create a new configured instance of {@link MethodInvoker}.
	 */
	private MethodInvoker createMethodInvoker(Object targetObject, String targetMethod) {
		HippyMethodInvoker invoker = new HippyMethodInvoker();
		invoker.setTargetObject(targetObject);
		invoker.setTargetMethod(targetMethod);
		invoker.setArguments(arguments);
		return invoker;
	}

	/**
	 * Prepare and invoke the invoker, rethrow checked exceptions as unchecked.
	 * @param invoker configured invoker
	 * @return return value of the invoked method
	 */
	@SuppressWarnings("unchecked")
	private T doInvoke(MethodInvoker invoker) throws Exception {
		try {
			invoker.prepare();
		}
		catch (ClassNotFoundException | NoSuchMethodException e) {
			throw new DynamicMethodInvocationException(e);
		}

		try {
			return (T) invoker.invoke();
		}
		catch (InvocationTargetException e) {
			if (e.getCause() instanceof Exception) {
				throw (Exception) e.getCause();
			}
			else {
				throw new InvocationTargetThrowableWrapper(e.getCause());
			}
		}
		catch (IllegalAccessException e) {
			throw new DynamicMethodInvocationException(e);
		}
	}

	@Override
	public void afterPropertiesSet() throws Exception {
		Assert.notNull(targetObject, "targetObject must not be null");
		Assert.hasLength(targetMethod, "targetMethod must not be empty");
		Assert.state(targetClassDeclaresTargetMethod(),
				"target class must declare a method with matching name and parameter types");
	}

	/**
	 * @return true if target class declares a method matching target method name with
	 * given number of arguments of appropriate type.
	 */
	private boolean targetClassDeclaresTargetMethod() {
		MethodInvoker invoker = createMethodInvoker(targetObject, targetMethod);

		Method[] memberMethods = invoker.getTargetClass().getMethods();
		Method[] declaredMethods = invoker.getTargetClass().getDeclaredMethods();

		List<Method> allMethods = new ArrayList<>();
		allMethods.addAll(Arrays.asList(memberMethods));
		allMethods.addAll(Arrays.asList(declaredMethods));

		String targetMethodName = invoker.getTargetMethod();

		for (Method method : allMethods) {
			if (method.getName().equals(targetMethodName)) {
				Class<?>[] params = method.getParameterTypes();
				if (arguments == null) {
					// don't check signature, assume arguments will be supplied
					// correctly at runtime
					return true;
				}
				if (arguments.length == params.length) {
					boolean argumentsMatchParameters = true;
					for (int j = 0; j < params.length; j++) {
						if (arguments[j] == null) {
							continue;
						}
						if (!(ClassUtils.isAssignableValue(params[j], arguments[j]))) {
							argumentsMatchParameters = false;
						}
					}
					if (argumentsMatchParameters) {
						return true;
					}
				}
			}
		}

		return false;
	}

	/**
	 * @param targetObject the delegate - bean id can be used to set this value in Spring
	 * configuration
	 */
	public void setTargetObject(Object targetObject) {
		this.targetObject = targetObject;
	}

	/**
	 * @param targetMethod name of the method to be invoked on
	 * {@link #setTargetObject(Object)}.
	 */
	public void setTargetMethod(String targetMethod) {
		this.targetMethod = targetMethod;
	}

	/**
	 * @param arguments arguments values for the { {@link #setTargetMethod(String)}. These
	 * will be used only when the subclass tries to invoke the target method without
	 * providing explicit argument values.
	 *
	 * If arguments are set to not-null value {@link #afterPropertiesSet()} will check the
	 * values are compatible with target method's signature. In case arguments are null
	 * (not set) method signature will not be checked and it is assumed correct values
	 * will be supplied at runtime.
	 */
	public void setArguments(Object[] arguments) {
		this.arguments = arguments == null ? null : Arrays.asList(arguments).toArray();
	}

	/**
	 * Return arguments.
	 * @return arguments
	 */
	protected Object[] getArguments() {
		return arguments;
	}

	/**
	 * Used to wrap a {@link Throwable} (not an {@link Exception}) thrown by a
	 * reflectively-invoked delegate.
	 *
	 * @author Robert Kasanicky
	 */
	@SuppressWarnings("serial")
	public static class InvocationTargetThrowableWrapper extends RuntimeException {

		public InvocationTargetThrowableWrapper(Throwable cause) {
			super(cause);
		}

	}

}

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