Spring中refresh分析之obtainFreshBeanFactory方法详解

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#获取BeanFactory

于 2016-11-21 10:46:33 首次发布

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本文深入分析Spring框架中AbstractApplicationContext的refresh方法之obtainFreshBeanFactory部分。主要介绍如何通过GenericApplicationContext获取并初始化beanFactory，包括刷新标志设置及序列化ID配置。

接上文AbstractApplicationContext中refresh方法详解我们分析过prepareRefresh后，本文分析obtainFreshBeanFactory方法。

该方法主要是获取到应用上下文维护的beanFactory，默认是DefaultListableBeanFactory 。

ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// AbstractApplicationContext
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
	refreshBeanFactory();
	return getBeanFactory();
}

① refreshBeanFactory

GenericApplicationContext的refreshBeanFactory方法。其首先应用CAS思想设置刷新标志，然后为beanFactory设置序列化ID-默认是application。

@Override
protected final void refreshBeanFactory() throws IllegalStateException {
	if (!this.refreshed.compareAndSet(false, true)) {
		throw new IllegalStateException(
				"GenericApplicationContext does not support multiple refresh attempts: just call 'refresh' once");
	}
	this.beanFactory.setSerializationId(getId());
}

当前对象this指的是AnnotationConfigServletWebServerApplicationContext，而refreshBeanFactory调用是其传递祖父类GenericApplicationContext 。GenericApplicationContext 内部如下所示维护了beanFactory。

public class GenericApplicationContext extends AbstractApplicationContext implements BeanDefinitionRegistry {

	private final DefaultListableBeanFactory beanFactory;

	@Nullable
	private ResourceLoader resourceLoader;

	private boolean customClassLoader = false;

	private final AtomicBoolean refreshed = new AtomicBoolean();
	
	public GenericApplicationContext() {
		this.beanFactory = new DefaultListableBeanFactory();
	}
	//...
}

② getBeanFactory

这里调用的仍旧是GenericApplicationContext的方法，如下所示，只是返回了内部维护的beanFactory，默认是DefaultListableBeanFactory。

@Override
public final ConfigurableListableBeanFactory getBeanFactory() {
	return this.beanFactory;
}

GenericApplicationContext关于BeanDefinition的行为比如get、remove，其实就是交给了beanFactory来处理。