spring-batch GenericApplicationContextFactory 源码

spring-batch GenericApplicationContextFactory 代码

文件路径：/spring-batch-core/src/main/java/org/springframework/batch/core/configuration/support/GenericApplicationContextFactory.java

/*
 * Copyright 2006-2022 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.core.configuration.support;

import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.support.DefaultListableBeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.support.GenericApplicationContext;
import org.springframework.context.support.GenericXmlApplicationContext;
import org.springframework.core.io.Resource;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * {@link ApplicationContextFactory} implementation that takes a parent context and a path
 * to the context to create. When the {@code createApplicationContext} method is called,
 * the child {@link ApplicationContext} is returned. The child context is not re-created
 * every time it is requested. It is lazily initialized and cached. Clients should ensure
 * that it is closed when it is no longer needed.
 */
public class GenericApplicationContextFactory extends AbstractApplicationContextFactory {

	/**
	 * Create an application context factory for the specified resource. The resource can
	 * be an actual {@link Resource} (in which case, it is interpreted as an XML file), or
	 * it can be a @Configuration class or a package name. All types must be the same
	 * (mixing XML with a Java package, for example, is not allowed and results in an
	 * {@link java.lang.IllegalArgumentException}).
	 * @param resources some resources (XML configuration files, @Configuration
	 * classes, or Java packages to scan)
	 */
	public GenericApplicationContextFactory(Object... resources) {
		super(resources);
	}

	/**
	 * @see AbstractApplicationContextFactory#createApplicationContext(ConfigurableApplicationContext,
	 * Object...)
	 */
	@Override
	protected ConfigurableApplicationContext createApplicationContext(ConfigurableApplicationContext parent,
			Object... resources) {
		ConfigurableApplicationContext context;

		if (allObjectsOfType(resources, Resource.class)) {
			context = new ResourceXmlApplicationContext(parent, resources);
		}
		else if (allObjectsOfType(resources, Class.class)) {
			context = new ResourceAnnotationApplicationContext(parent, resources);
		}
		else if (allObjectsOfType(resources, String.class)) {
			context = new ResourceAnnotationApplicationContext(parent, resources);
		}
		else {
			List<Class<?>> types = new ArrayList<>();
			for (Object resource : resources) {
				types.add(resource.getClass());
			}
			throw new IllegalArgumentException(
					"No application context could be created for resource types: " + Arrays.toString(types.toArray()));
		}

		return context;
	}

	private boolean allObjectsOfType(Object[] objects, Class<?> type) {
		for (Object object : objects) {
			if (!type.isInstance(object)) {
				return false;
			}
		}
		return true;
	}

	private abstract class ApplicationContextHelper {

		private final DefaultListableBeanFactory parentBeanFactory;

		private final ConfigurableApplicationContext parent;

		public ApplicationContextHelper(ConfigurableApplicationContext parent, GenericApplicationContext context,
				Object... config) {
			this.parent = parent;
			if (parent != null) {
				Assert.isTrue(parent.getBeanFactory() instanceof DefaultListableBeanFactory,
						"The parent application context must have a bean factory of type DefaultListableBeanFactory");
				parentBeanFactory = (DefaultListableBeanFactory) parent.getBeanFactory();
			}
			else {
				parentBeanFactory = null;
			}
			context.setParent(parent);
			context.setId(generateId(config));
			loadConfiguration(config);
			prepareContext(parent, context);
		}

		protected abstract String generateId(Object... configs);

		protected abstract void loadConfiguration(Object... configs);

		protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
			if (parentBeanFactory != null) {
				GenericApplicationContextFactory.this.prepareBeanFactory(parentBeanFactory, beanFactory);
				for (Class<? extends BeanFactoryPostProcessor> cls : getBeanFactoryPostProcessorClasses()) {
					for (String name : parent.getBeanNamesForType(cls)) {
						beanFactory.registerSingleton(name, (parent.getBean(name)));
					}
				}
			}
		}

	}

	private final class ResourceXmlApplicationContext extends GenericXmlApplicationContext {

		private final ApplicationContextHelper helper;

		/**
		 * @param parent
		 */
		public ResourceXmlApplicationContext(ConfigurableApplicationContext parent, Object... resources) {

			class ResourceXmlApplicationContextHelper extends ApplicationContextHelper {

				ResourceXmlApplicationContextHelper(ConfigurableApplicationContext parent,
						GenericApplicationContext context, Object... config) {
					super(parent, context, config);
				}

				@Override
				protected String generateId(Object... configs) {
					Resource[] resources = Arrays.copyOfRange(configs, 0, configs.length, Resource[].class);
					try {
						List<String> uris = new ArrayList<>();
						for (Resource resource : resources) {
							uris.add(resource.getURI().toString());
						}
						return StringUtils.collectionToCommaDelimitedString(uris);
					}
					catch (IOException e) {
						return Arrays.toString(resources);
					}
				}

				@Override
				protected void loadConfiguration(Object... configs) {
					Resource[] resources = Arrays.copyOfRange(configs, 0, configs.length, Resource[].class);
					load(resources);
				}

			}
			helper = new ResourceXmlApplicationContextHelper(parent, this, resources);
			refresh();
		}

		@Override
		protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
			super.prepareBeanFactory(beanFactory);
			helper.prepareBeanFactory(beanFactory);
		}

		@Override
		public String toString() {
			return "ResourceXmlApplicationContext:" + getId();
		}

	}

	private final class ResourceAnnotationApplicationContext extends AnnotationConfigApplicationContext {

		private final ApplicationContextHelper helper;

		public ResourceAnnotationApplicationContext(ConfigurableApplicationContext parent, Object... resources) {

			class ResourceAnnotationApplicationContextHelper extends ApplicationContextHelper {

				public ResourceAnnotationApplicationContextHelper(ConfigurableApplicationContext parent,
						GenericApplicationContext context, Object... config) {
					super(parent, context, config);
				}

				@Override
				protected String generateId(Object... configs) {
					if (allObjectsOfType(configs, Class.class)) {
						Class<?>[] types = Arrays.copyOfRange(configs, 0, configs.length, Class[].class);
						List<String> names = new ArrayList<>();
						for (Class<?> type : types) {
							names.add(type.getName());
						}
						return StringUtils.collectionToCommaDelimitedString(names);
					}
					else {
						return Arrays.toString(configs);
					}
				}

				@Override
				protected void loadConfiguration(Object... configs) {
					if (allObjectsOfType(configs, Class.class)) {
						Class<?>[] types = Arrays.copyOfRange(configs, 0, configs.length, Class[].class);
						register(types);
					}
					else {
						String[] pkgs = Arrays.copyOfRange(configs, 0, configs.length, String[].class);
						scan(pkgs);
					}
				}

			}
			helper = new ResourceAnnotationApplicationContextHelper(parent, this, resources);
			refresh();
		}

		@Override
		protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
			super.prepareBeanFactory(beanFactory);
			helper.prepareBeanFactory(beanFactory);
		}

		@Override
		public String toString() {
			return "ResourceAnnotationApplicationContext:" + getId();
		}

	}

}

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