com.gitlab.spacetrucker.modularspringcontexts.module.ModularSpringContextsModuleBean Maven / Gradle / Ivy

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package com.gitlab.spacetrucker.modularspringcontexts.module;

import java.util.List;
import java.util.concurrent.Executor;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.xml.NamespaceHandlerResolver;
import org.springframework.beans.factory.xml.XmlBeanDefinitionReader;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.support.AbstractXmlApplicationContext;

/**
 * This implementation is used to represent a module. A module is merely a
 * spring application context. It has support for a custom
 * {@link NamespaceHandlerResolver} to allow extensible XML authoring of spring
 * beans schema. The actual startup is done via a {@link #moduleStarter} to
 * allow parallel module startup. This module can depend upon a number of
 * predefined modules. Bean imports are possible from these modules.
 * 
 * The {@code module} element of {@code modular-spring-contexts.xsd} will cause
 * an initialization of an instance of this type.
 */
public class ModularSpringContextsModuleBean extends AbstractXmlApplicationContext implements ApplicationContextAware {

	private NamespaceHandlerResolver customNamespaceHandlerResolver;

	private List requiredModules;

	private Executor moduleStarter = new SameThreadExecutor();

	private ApplicationContext moduleHost;

	@Override
	protected void initBeanDefinitionReader(XmlBeanDefinitionReader reader) {
		super.initBeanDefinitionReader(reader);
		reader.setNamespaceHandlerResolver(customNamespaceHandlerResolver);
	}

	public void setCustomNamespaceHandlerResolver(NamespaceHandlerResolver customNamespaceHandlerResolver) {
		this.customNamespaceHandlerResolver = customNamespaceHandlerResolver;
	}

	public void setRequiredModules(List requiredModules) {
		this.requiredModules = requiredModules;
	}

	public void setModuleStarter(Executor moduleStarter) {
		this.moduleStarter = moduleStarter;
	}

	@Override
	public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
		this.moduleHost = applicationContext;
	}

	/**
	 * Adds the modules this module depends upon as singleton beans to the bean
	 * factory of this application context.
	 */
	@Override
	protected void onRefresh() throws BeansException {
		super.onRefresh();
		for (String requiredModule : requiredModules) {
			if (getBeanFactory().containsBeanDefinition(requiredModule)) {
				throw new IllegalStateException(
						"The name of module " + requiredModule + " is already registered as a bean definition.");
			}
			getBeanFactory().registerSingleton(requiredModule,
					moduleHost.getBean(requiredModule, ApplicationContext.class));
		}
	}

	@Override
	public void afterPropertiesSet() {
		if (!isActive()) {
			moduleStarter.execute(new Runnable() {
				@Override
				public void run() {
					refresh();
				}
			});
		}
	}
}