spring解决循环依赖问题

最新推荐文章于 2024-03-26 15:29:22 发布

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最新推荐文章于 2024-03-26 15:29:22 发布

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文章标签： spring ar java

本文链接：https://blog.youkuaiyun.com/m0_63723856/article/details/121187046

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本文探讨了Spring框架如何解决循环依赖问题。通过代码分析，详细解释了在`AbstractAutowireCapableBeanFactory`的`doCreateBean`方法中，Spring如何利用一级、二级和三级缓存来避免循环依赖导致的错误。当A和B类发生循环依赖时，Spring会尝试将未完整初始化的对象放入缓存，在后续的依赖注入中查找并完成实例化，从而防止错误的发生。

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@SuppressWarnings("unchecked")
	protected <T> T doGetBean(
			String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly)
			throws BeansException {

		String beanName = transformedBeanName(name);
		Object beanInstance;

		// Eagerly check singleton cache for manually registered singletons.
		Object sharedInstance = getSingleton(beanName);
		if (sharedInstance != null && args == null) {
			if (logger.isTraceEnabled()) {
				if (isSingletonCurrentlyInCreation(beanName)) {
					logger.trace("Returning eagerly cached instance of singleton bean '" + beanName +
							"' that is not fully initialized yet - a consequence of a circular reference");
				}
				else {
					logger.trace("Returning cached instance of singleton bean '" + beanName + "'");
				}
			}
			beanInstance = getObjectForBeanInstance(sharedInstance, name, beanName, null);
		}

		else {
			// Fail if we're already creating this bean instance:
			// We're assumably within a circular reference.
			if (isPrototypeCurrentlyInCreation(beanName)) {
				throw new BeanCurrentlyInCreationException(beanName);
			}

			// Check if bean definition exists in this factory.
			BeanFactory parentBeanFactory = getParentBeanFactory();
			if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
				// Not found -> check parent.
				String nameToLookup = originalBeanName(name);
				if (parentBeanFactory instanceof AbstractBeanFactory) {
					return ((

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