Spring源码分析(3)——Bean实例化代码分析

protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) {
	// Make sure bean class is actually resolved at this point.
	Class<?> beanClass = resolveBeanClass(mbd, beanName);

	if (beanClass != null && !Modifier.isPublic(beanClass.getModifiers()) && !mbd.isNonPublicAccessAllowe()) {
		throw new BeanCreationException(mbd.getResourceDescription(), beanName,
				"Bean class isn't public, and non-public access not allowed: " + beanClass.getName());
	}

	Supplier<?> instanceSupplier = mbd.getInstanceSupplier();
	if (instanceSupplier != null) {
		return obtainFromSupplier(instanceSupplier, beanName);
	}

	if (mbd.getFactoryMethodName() != null)  {
		return instantiateUsingFactoryMethod(beanName, mbd, args);
	}

	// Shortcut when re-creating the same bean...
	boolean resolved = false;
	boolean autowireNecessary = false;
	if (args == null) {
		synchronized (mbd.constructorArgumentLock) {
			if (mbd.resolvedConstructorOrFactoryMethod != null) {
				resolved = true;
				autowireNecessary = mbd.constructorArgumentsResolved;
			}
		}
	}
	if (resolved) {
		if (autowireNecessary) {
			return autowireConstructor(beanName, mbd, null, null);
		}
		else {
			return instantiateBean(beanName, mbd);
		}
	}

	// Need to determine the constructor...
	Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName);
	if (ctors != null ||
			mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_CONSTRUCTOR ||
			mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args))  {
     	//使用有参构造函数实例化
		return autowireConstructor(beanName, mbd, ctors, args);
	}

  	//使用无参构造函数实例化
	// No special handling: simply use no-arg constructor.
	return instantiateBean(beanName, mbd);
}

protected BeanWrapper instantiateBean(final String beanName, final RootBeanDefinition mbd) {
......
	beanInstance = getInstantiationStrategy().instantiate(mbd, beanName, parent);
......

public Object instantiate(RootBeanDefinition bd, @Nullable String beanName, BeanFactory owner) {
......
	{
		return BeanUtils.instantiateClass(constructorToUse);
	} else {
    	//使用CGLIB来实例化对象
		// Must generate CGLIB subclass.
		return instantiateWithMethodInjection(bd, beanName, owner);
	}
......

public static <T> T instantiateClass(Constructor<T> ctor, Object... args) throws BeanInstantiationException {
		Assert.notNull(ctor, "Constructor must not be null");
	try {
		ReflectionUtils.makeAccessible(ctor);
		return (KotlinDetector.isKotlinType(ctor.getDeclaringClass()) ?
				KotlinDelegate.instantiateClass(ctor, args) : ctor.newInstance(args));
	}
	......