第三章 spring-bean之DefaultListableBeanFactory（7）

前言

DefaultListableBeanFactory是beanFactory體系裏面最後一個子類，也是惟一的操做類，惟一的實現。DefaultListableBeanFactory繼承了AbstractAutowireCapableBeanFactory，實現了ConfigurableListableBeanFactory接口。

解讀變量

allowBeanDefinitionOverriding變量

allowBeanDefinitionOverriding是一個坑，DefaultListableBeanFactory重寫了父類SimpleAliasRegistry的allowAliasOverriding方法。重寫的allowAliasOverriding方法就是使用的allowBeanDefinitionOverriding。若是要修改allowBeanDefinitionOverriding變量，須要深刻的考慮SimpleAliasRegistry的行爲。

private boolean allowBeanDefinitionOverriding = true;
public boolean isAllowBeanDefinitionOverriding() {
		return this.allowBeanDefinitionOverriding;
}
protected boolean allowAliasOverriding() {
	return isAllowBeanDefinitionOverriding();
}

public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition) throws BeanDefinitionStoreException {
	oldBeanDefinition = this.beanDefinitionMap.get(beanName);
	if (oldBeanDefinition != null) {
		if (!isAllowBeanDefinitionOverriding()) {
			throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
												   "Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName +
												   "': There is already [" + oldBeanDefinition + "] bound.");
		}
	}
	......
			
}

解讀

1. 修改allowBeanDefinitionOverriding，注意SimpleAliasRegistry的行爲
2. allowBeanDefinitionOverriding的做用是是否容許一個name有多個BeanDefinition

dependencyComparator變量

private Comparator<Object> dependencyComparator;

解讀

細節請看第二章 一節spring-core之comparator深刻解讀

resolvableDependencies

private final Map<Class<?>, Object> resolvableDependencies = new ConcurrentHashMap<Class<?>, Object>(16);


public void registerResolvableDependency(Class<?> dependencyType, Object autowiredValue) {
		Assert.notNull(dependencyType, "Dependency type must not be null");
		if (autowiredValue != null) {
			if (!(autowiredValue instanceof ObjectFactory || dependencyType.isInstance(autowiredValue))) {
				throw new IllegalArgumentException("Value [" + autowiredValue +"] does not implement specified dependency type [" + dependencyType.getName() + "]");
			}
			this.resolvableDependencies.put(dependencyType, autowiredValue);
		}
}

AbstractApplicationContext

protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
		// BeanFactory interface not registered as resolvable type in a plain factory.
		// MessageSource registered (and found for autowiring) as a bean.
		beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
		beanFactory.registerResolvableDependency(ResourceLoader.class, this);
		beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
		beanFactory.registerResolvableDependency(ApplicationContext.class, this);
}

解讀

resolvableDependencies用來保存spring中本身的bean。這樣隔離系統bean與業務bean，好像spring，沒有作得完全。

beanDefinitionMap屬性

private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<String, BeanDefinition>(256);

保存BeanDefinition的實現類，

allBeanNamesByType屬性 與 singletonBeanNamesByType變量

private final Map<Class<?>, String[]> allBeanNamesByType = new ConcurrentHashMap<Class<?>, String[]>(64);

private final Map<Class<?>, String[]> singletonBeanNamesByType = new ConcurrentHashMap<Class<?>, String[]>(64);

public String[] getBeanNamesForType(Class<?> type, boolean includeNonSingletons, boolean allowEagerInit) {
		if (!isConfigurationFrozen() || type == null || !allowEagerInit) {
			return doGetBeanNamesForType(ResolvableType.forRawClass(type), includeNonSingletons, allowEagerInit);
		}
		Map<Class<?>, String[]> cache =
				(includeNonSingletons ? this.allBeanNamesByType : this.singletonBeanNamesByType);
		String[] resolvedBeanNames = cache.get(type);
		if (resolvedBeanNames != null) {
			return resolvedBeanNames;
		}
		resolvedBeanNames = doGetBeanNamesForType(ResolvableType.forRawClass(type), includeNonSingletons, true);
		if (ClassUtils.isCacheSafe(type, getBeanClassLoader())) {
			cache.put(type, resolvedBeanNames);
		}
		return resolvedBeanNames;
	}

當getBeanNamesForType方法被調用的時候，會把結果緩存到allBeanNamesByType或singletonBeanNamesByType裏面。getBeanNamesForType參數type對應class類型的全部beanName

beanDefinitionNames與manualSingletonNames變量

private volatile List<String> beanDefinitionNames = new ArrayList<String>(256);

private volatile Set<String> manualSingletonNames = new LinkedHashSet<String>(16);

public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition) throws BeanDefinitionStoreException {

		if (hasBeanCreationStarted()) {
			// Cannot modify startup-time collection elements anymore (for stable iteration)
			synchronized (this.beanDefinitionMap) {
				this.beanDefinitionMap.put(beanName, beanDefinition);
				List<String> updatedDefinitions = new ArrayList<String>(this.beanDefinitionNames.size() + 1);
				updatedDefinitions.addAll(this.beanDefinitionNames);
				updatedDefinitions.add(beanName);
				this.beanDefinitionNames = updatedDefinitions;
				if (this.manualSingletonNames.contains(beanName)) {// beanDefinitionNames 存在的beanName，就不能在manualSingletonNames存在
					Set<String> updatedSingletons = new LinkedHashSet<String>(this.manualSingletonNames);
					updatedSingletons.remove(beanName);
					this.manualSingletonNames = updatedSingletons;
				}
			}
		}
		
}

public void registerSingleton(String beanName, Object singletonObject) throws IllegalStateException {
	super.registerSingleton(beanName, singletonObject);

	if (hasBeanCreationStarted()) {
		// Cannot modify startup-time collection elements anymore (for stable iteration)
		synchronized (this.beanDefinitionMap) {
			if (!this.beanDefinitionMap.containsKey(beanName)) {
				Set<String> updatedSingletons = new LinkedHashSet<String>(this.manualSingletonNames.size() + 1);
				updatedSingletons.addAll(this.manualSingletonNames);
				updatedSingletons.add(beanName);
				this.manualSingletonNames = updatedSingletons;
			}
		}
	}
	else {
		// Still in startup registration phase
		if (!this.beanDefinitionMap.containsKey(beanName)) {
			this.manualSingletonNames.add(beanName);
		}
	}

	clearByTypeCache();
}

beanDefinitionNames保存全部BeanDefinition的名字，manualSingletonNames保存了全部singleton的BeanDefinitionName。注意beanDefinitionNames聲明瞭 volatile