前言：
spring bean 的生命周期粗糙的分为以下步骤。
实例化（创建一个属性都为空的对象）---------》属性填充（populateBean，下文中这个步骤我都称为初始化）-----------》init方法的执行（invokerInitMethods，下文称为init）
postprocessor的方法就是穿插在这三个大的步骤中。
BeanPostProcessor：
postProcessBeforeInitialization调用时机
向上找调用者：
继续向上：
看以看出populateBean(初始化bean)-------------------》beanpostBeforeInitialization---------------------------------->invokeinitMethods(配置的init-method)
postProcessAfterInitialization调用时机：
向上：
可以看出在init-method方法之后
看以看出populateBean(初始化bean)-------------------》beanpostBeforeInitialization---------------------------------->invokeinitMethods(配置的init-method)------->postProcessAfterInitialization
public class MBeanPostProcessor implements BeanPostProcessor {
@Override
//populateBean之后 invokeinitMethods之前
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
System.out.println("post bean before! ："+beanName);
return bean;
}
@Override
//invokeinitMethods之后
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
System.out.println("post bean after!"+beanName);
return bean;
}
}另一个重要的是：
InstantiationAwareBeanPostProcessor
postProcessBeforeInstantiation调用时机：
向上找调用者：
继续向上：
可以看出是在实例化之前：（也就是反射创建对象之前，如果postProcessBeforeInstantiation创建了一个非空的对象，则不会走实例化步骤。）
postProcessAfterInstantiation调用时机：protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {
PropertyValues pvs = mbd.getPropertyValues();
if (bw == null) {
if (!pvs.isEmpty()) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance");
}
else {
// Skip property population phase for null instance.
return;
}
}
// 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.
boolean continueWithPropertyPopulation = true;
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
//在这里执行
if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
continueWithPropertyPopulation = false;
break;
}
}
}
}
if (!continueWithPropertyPopulation) {
return;
}
省略。。。。。
applyPropertyValues(beanName, mbd, bw, pvs);
}
可以看出是在在初始化之前，具体是属性填充之前。（初始化之前，实例化之后） 如果返回fales，则不会继续初始化，即不会属性填充。postProcessPropertyValues调用时机：protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {
PropertyValues pvs = mbd.getPropertyValues();
if (bw == null) {
if (!pvs.isEmpty()) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance");
}
else {
// Skip property population phase for null instance.
return;
}
}
// 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.
boolean continueWithPropertyPopulation = true;
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
continueWithPropertyPopulation = false;
break;
}
}
}
}
if (!continueWithPropertyPopulation) {
return;
}
if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME ||
mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
// Add property values based on autowire by name if applicable.
if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) {
autowireByName(beanName, mbd, bw, newPvs);
}
// Add property values based on autowire by type if applicable.
if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
autowireByType(beanName, mbd, bw, newPvs);
}
pvs = newPvs;
}
boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
boolean needsDepCheck = (mbd.getDependencyCheck() != RootBeanDefinition.DEPENDENCY_CHECK_NONE);
if (hasInstAwareBpps || needsDepCheck) {
PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
if (hasInstAwareBpps) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
if (pvs == null) {
return;
}
}
}
}
if (needsDepCheck) {
checkDependencies(beanName, mbd, filteredPds, pvs);
}
}
applyPropertyValues(beanName, mbd, bw, pvs);
}在postProcessAfterInstantiation之后，applyPropertyValues之前。（属性填充之前修改属性值）
总结： 执行顺序
1.postProcessBeforeInstantiation(实现这个方法可以做自定义实例化)
2.实例化
3.postProcessAfterInstantiation（是否要初始化）
4.postProcessPropertyValues（修改属性）
5.初始化（属性填充）（populateBean）
6.postProcesstBeforeInitialization( 自定义init方法执行之前)
7.invokeinitMethods(执行自定义的init方法)
8.postProcessAfterInitialization(自定义init方法执行之后)
如果加上aware
1.postProcessBeforeInstantiation(实现这个方法可以做自定义实例化)
2.实例化
3.postProcessAfterInstantiation（是否要初始化）
4.postProcessPropertyValues（修改属性）
5.初始化（属性填充）（populateBean）
6.postProcesstBeforeInitialization( 自定义init方法执行之前)
7.invokeAwareMethod
8.invokeinitMethods(执行自定义的init方法)
9.postProcessAfterInitialization(自定义init方法执行之后)