simpleinstantiationstrategy.java

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/*
 * Copyright 2002-2007 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
 *
 *      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.springframework.beans.factory.support;

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

import org.springframework.beans.BeanInstantiationException;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.BeanDefinitionStoreException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.util.StringUtils;

/**
 * Simple object instantiation strategy for use in a BeanFactory.
 *
 * <p>Does not support Method Injection, although it provides hooks for subclasses
 * to override to add Method Injection support, for example by overriding methods.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @since 1.1
 */
public class SimpleInstantiationStrategy implements InstantiationStrategy {

	public Object instantiate(
			RootBeanDefinition beanDefinition, String beanName, BeanFactory owner) {

		// Don't override the class with CGLIB if no overrides.
		if (beanDefinition.getMethodOverrides().isEmpty()) {
			Constructor constructorToUse = (Constructor) beanDefinition.resolvedConstructorOrFactoryMethod;
			if (constructorToUse == null) {
				Class clazz = beanDefinition.getBeanClass();
				if (clazz.isInterface()) {
					throw new BeanInstantiationException(clazz, "Specified class is an interface");
				}
				try {
					constructorToUse = clazz.getDeclaredConstructor((Class[]) null);
					beanDefinition.resolvedConstructorOrFactoryMethod = constructorToUse;
				}
				catch (Exception ex) {
					throw new BeanInstantiationException(clazz, "No default constructor found", ex);
				}
			}
			return BeanUtils.instantiateClass(constructorToUse, null);
		}
		else {
			// Must generate CGLIB subclass.
			return instantiateWithMethodInjection(beanDefinition, beanName, owner);
		}
	}

	/**
	 * Subclasses can override this method, which is implemented to throw
	 * UnsupportedOperationException, if they can instantiate an object with
	 * the Method Injection specified in the given RootBeanDefinition.
	 * Instantiation should use a no-arg constructor.
	 */
	protected Object instantiateWithMethodInjection(
			RootBeanDefinition beanDefinition, String beanName, BeanFactory owner) {

		throw new UnsupportedOperationException(
				"Method Injection not supported in SimpleInstantiationStrategy");
	}

	public Object instantiate(
			RootBeanDefinition beanDefinition, String beanName, BeanFactory owner,
			Constructor ctor, Object[] args) {

		if (beanDefinition.getMethodOverrides().isEmpty()) {
			return BeanUtils.instantiateClass(ctor, args);
		}
		else {
			return instantiateWithMethodInjection(beanDefinition, beanName, owner, ctor, args);
		}
	}

	/**
	 * Subclasses can override this method, which is implemented to throw
	 * UnsupportedOperationException, if they can instantiate an object with
	 * the Method Injection specified in the given RootBeanDefinition.
	 * Instantiation should use the given constructor and parameters.
	 */
	protected Object instantiateWithMethodInjection(
			RootBeanDefinition beanDefinition, String beanName, BeanFactory owner,
			Constructor ctor, Object[] args) {

		throw new UnsupportedOperationException(
				"Method Injection not supported in SimpleInstantiationStrategy");
	}

	public Object instantiate(
			RootBeanDefinition beanDefinition, String beanName, BeanFactory owner,
			Object factoryBean, Method factoryMethod, Object[] args) {

		try {
			// It's a static method if the target is null.
			if (!Modifier.isPublic(factoryMethod.getModifiers()) ||
					!Modifier.isPublic(factoryMethod.getDeclaringClass().getModifiers())) {
				factoryMethod.setAccessible(true);
			}
			return factoryMethod.invoke(factoryBean, args);
		}
		catch (IllegalArgumentException ex) {
			throw new BeanDefinitionStoreException(
					"Illegal arguments to factory method [" + factoryMethod + "]; " +
					"args: " + StringUtils.arrayToCommaDelimitedString(args));
		}
		catch (IllegalAccessException ex) {
			throw new BeanDefinitionStoreException(
					"Cannot access factory method [" + factoryMethod + "]; is it public?");
		}
		catch (InvocationTargetException ex) {
			throw new BeanDefinitionStoreException(
					"Factory method [" + factoryMethod + "] threw exception", ex.getTargetException());
		}
	}

}