Spring源码之Bean生命周期

https://www.jianshu.com/p/1dec08d290c1
https://www.cnblogs.com/zrtqsk/p/3735273.html

总结

1. 将class文件加载成BeanDefinition，并向IOC容器中进行注册
2. 在实例化前，能通过实现BeanFactoryPostProcessor，进行BeanDefinition注册，设置Bean属性值等功能
3. 在createBean时，实现SmartInstantiationAwareBeanPostProcessor或InstantiationAwareBeanPostProcessor接口的postProcessBeforeInstantiation的方法
4. Bean 实例化（createBeanInstance）
5. 实现InstantiationAwareBeanPostProcessor接口，在populateBean中调用postProcessAfterInstantiation
6. initializeBean时，调用invokeAwareMethods()，实现类通过实现BeanFactoryAware, BeanNameAware进行自定义一些功能
7. 实现BeanPostProcessor的postProcessBeforeInitialization()
8. @PostConstruct
9. invokeInitMethods反射方式进行初始化
10. afterPropertiesSet()，初始化后进行属性设置
11. BeanPostProcessor#postProcessAfterInitialization（）
12. @PreDestroy
13. destroy（）

加载成BeanDefinition，并向IOC容器中进行注册

详见前文《Spring源码之IOC容器创建、BeanDefinition加载和注册和IOC容器依赖注入》

BeanFactoryPostProcessor#invokeBeanFactoryPostProcessors()

在PostProcessorRegistrationDelegate#invokeBeanFactoryPostProcessors()方法中完成invokeBeanDefinitionRegistryPostProcessors() BeanDefinition的注册后，会调用各BeanFactoryPostProcessor的postProcessBeanFactory方法，此时可自定义实现BeanFactoryPostProcessor的postProcessBeanFactory方法，进行属性添加等功能。

一个例子：

@Component
public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
    int i = 1;

    public MyBeanFactoryPostProcessor() {
        super();
        System.out.println("这是BeanFactoryPostProcessor实现类构造器！！");
    }

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)
            throws BeansException {

        if(beanFactory.getBeanDefinition("person") != null && i == 1) {
            i--;
            System.out.println("BeanFactoryPostProcessor调用postProcessBeanFactory方法");
        }

        BeanDefinition bd = beanFactory.getBeanDefinition("person");
        bd.getPropertyValues().addPropertyValue("name", "Carl");
    }
}

postProcessBeforeInstantiation()

在createBean时，实例化(Instantiation Bean)前，自定义实现SmartInstantiationAwareBeanPostProcessor接口的postProcessBeforeInstantiation的方法，可做一些自定义处理。

@Override
protected Object createBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) throws BeanCreationException {
    // Give BeanPostProcessors a chance to return a proxy instead of the target bean instance.
	Object bean = resolveBeforeInstantiation(beanName, mbdToUse);
	......
}

一个例子：

@Component
public class MyInstantiationAwareBeanPostProcessor implements SmartInstantiationAwareBeanPostProcessor {

    // 接口方法、实例化Bean之前调用
    @Override
    public Object postProcessBeforeInstantiation(Class beanClass,String beanName) throws BeansException {

        if(beanName.equals("person")) {
            System.out.println("InstantiationAwareBeanPostProcessor调用postProcessBeforeInstantiation方法");
        }
        return null;
    }
}

实例化时初始化构造器

由AbstractAutowireCapableBeanFactory#doCreateBean()入口，通过createBeanInstance去进行实例化

protected Object doCreateBean(String beanName, RootBeanDefinition mbd, @Nullable Object[] args)
			throws BeanCreationException {
    if (instanceWrapper == null) {
		instanceWrapper = createBeanInstance(beanName, mbd, args);
	}
	......
}

SimpleInstantiationStrategy#instantiate()

@Override
public Object instantiate(RootBeanDefinition bd, @Nullable String beanName, BeanFactory owner) {
    ......
    return BeanUtils.instantiateClass(constructorToUse);
}

postProcessAfterInstantiation

在AbstractAutowireCapableBeanFactory#populateBean()中

protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {
	......

	// Give any InstantiationAwareBeanPostProcessors the opportunity to modify the
	// state of the bean before properties are set. This can be used, for example,
	// to support styles of field injection.
	if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
		for (InstantiationAwareBeanPostProcessor bp : getBeanPostProcessorCache().instantiationAware) {
			if (!bp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
				return;
			}
		}
	}
}

postProcessPropertyValues()

protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {

		PropertyDescriptor[] filteredPds = null;
		if (hasInstAwareBpps) {
			for (InstantiationAwareBeanPostProcessor bp : getBeanPostProcessorCache().instantiationAware) {
				if (pvsToUse == null) {
					......
					pvsToUse = bp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
					......
				}
				pvs = pvsToUse;
			}
		}
	}

例子：

@Component
public class MyInstantiationAwareBeanPostProcessor implements SmartInstantiationAwareBeanPostProcessor {
    // 接口方法、设置某个属性时调用
    @Override
    public PropertyValues postProcessPropertyValues(PropertyValues pvs,PropertyDescriptor[] pds, Object bean, String beanName)
            throws BeansException {
        if(beanName.equals("person")) {
            System.out.println("InstantiationAwareBeanPostProcessor调用postProcessPropertyValues方法");
        }

        return pvs;
    }
}

invokeAwareMethods()

private void invokeAwareMethods(String beanName, Object bean) {
	if (bean instanceof Aware) {
		if (bean instanceof BeanNameAware) {
			((BeanNameAware) bean).setBeanName(beanName);
		}
		if (bean instanceof BeanClassLoaderAware) {
			ClassLoader bcl = getBeanClassLoader();
			if (bcl != null) {
				((BeanClassLoaderAware) bean).setBeanClassLoader(bcl);
			}
		}
		if (bean instanceof BeanFactoryAware) {
			((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);
		}
	}
}

例子：

@Component
public class Person implements BeanFactoryAware, BeanNameAware,InitializingBean, DisposableBean {
    @Override
    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
        System.out.println("【BeanFactoryAware接口】调用BeanFactoryAware.setBeanFactory()");
        this.beanFactory = beanFactory;
    }

    // 这是BeanNameAware接口方法
    @Override
    public void setBeanName(String beanName) {
        System.out.println("【BeanNameAware接口】调用BeanNameAware.setBeanName()");
        this.beanName = beanName;
    }
}

postProcessBeforeInitialization()

执行初始化

exposedObject = initializeBean(beanName, exposedObject, mbd);

protected Object initializeBean(String beanName, Object bean, @Nullable RootBeanDefinition mbd) {
	......
	Object wrappedBean = bean;
	if (mbd == null || !mbd.isSynthetic()) {
		wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
	}
}

一个例子：

@Component
public class MyBeanPostProcessor implements BeanPostProcessor {
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName)
            throws BeansException {
        if(beanName.equals("person")) {
            System.out.println("BeanPostProcessor接口方法postProcessBeforeInitialization对属性进行更改！");
        }
        return bean;
    }
}

@PostConstruct

InitDestroyAnnotationBeanPostProcessor#postProcessBeforeInitialization()

通过反射方式去调用@PostConstruct注解的方法

@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
	LifecycleMetadata metadata = findLifecycleMetadata(bean.getClass());
	try {
		metadata.invokeInitMethods(bean, beanName);
	}
	......
	return bean;
}

例子：

@PostConstruct
public void myInit() {
    System.out.println("【init-method】调用<bean>的init-method属性指定的初始化方法");
}

初始化（invokeInitMethods）

AbstractAutowireCapableBeanFactory#initializeBean()

protected Object initializeBean(String beanName, Object bean, @Nullable RootBeanDefinition mbd) {
    try {
		invokeInitMethods(beanName, wrappedBean, mbd);
	}
}

afterPropertiesSet()

AbstractAutowireCapableBeanFactory#invokeInitMethods()

protected void invokeInitMethods(String beanName, Object bean, @Nullable RootBeanDefinition mbd)
		throws Throwable {

	((InitializingBean) bean).afterPropertiesSet();
    .......
}

BeanPostProcessor#postProcessAfterInitialization（）

protected Object initializeBean(String beanName, Object bean, @Nullable RootBeanDefinition mbd) {
	if (mbd == null || !mbd.isSynthetic()) {
		wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
	}
	......
}

例子：

@Component
public class MyBeanPostProcessor implements BeanPostProcessor {
    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName)
            throws BeansException {
        if(beanName.equals("person")){
            System.out.println("BeanPostProcessor接口方法postProcessAfterInitialization对属性进行更改！");
        }

        return bean;
    }
}

@PreDestroy

在DisposableBeanAdapter#destroy()方法中，调用InitDestroyAnnotationBeanPostProcessor#postProcessBeforeDestruction(),最后通过反射执行@PreDestroy方法

@Override
public void destroy() {
	if (!CollectionUtils.isEmpty(this.beanPostProcessors)) {
		for (DestructionAwareBeanPostProcessor processor : this.beanPostProcessors) {
			processor.postProcessBeforeDestruction(this.bean, this.beanName);
		}
	}
}

例子

@Component
public class Person implements BeanFactoryAware, BeanNameAware,InitializingBean, DisposableBean {
    @PreDestroy
    public void myDestory() {
        System.out.println("【destroy-method】调用<bean>的destroy-method属性指定的初始化方法");
    }
}

destroy

@Component
public class Person implements BeanFactoryAware, BeanNameAware,InitializingBean, DisposableBean {
    @Override
    public void destroy() throws Exception {
        System.out.println("【DiposibleBean接口】调用DiposibleBean.destory()");
    }
}