- 处理器扩展点流程图
- resolveBeforeInstantiation实例化之前
-
- applyBeanPostProcessorsBeforeInstantiation实例化之前
-
- applyBeanPostProcessorsAfterInitialization初始化
- 扩展点实战
-
- MyInstantiationAwareBeanPostProcessor扩展类
- 测试代码
处理器扩展点流程图
先把这个图送上，在创建bean的过程中基本就是这些了，可能还有其他地方我漏了，看到的大神提醒下啊，下次补。然后我们一个个来将下这些扩展点能做什么。
resolveBeforeInstantiation实例化之前
在实例化之前吃
@Nullable
protected Object resolveBeforeInstantiation(String beanName, RootBeanDefinition mbd) {
Object bean = null;
if (!Boolean.FALSE.equals(mbd.beforeInstantiationResolved)) {
// Make sure bean class is actually resolved at this point.
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
//非合成的，且有InstantiationAwareBeanPostProcessors
Class<?> targetType = determineTargetType(beanName, mbd);//获取类型
if (targetType != null) {
bean = applyBeanPostProcessorsBeforeInstantiation(targetType, beanName);
if (bean != null) {
bean = applyBeanPostProcessorsAfterInitialization(bean, beanName);
}
}
}
mbd.beforeInstantiationResolved = (bean != null);//是否解析了
}
return bean;
}
applyBeanPostProcessorsBeforeInstantiation实例化之前
InstantiationAwareBeanPostProcessor接口的处理器处理，比如可以把一个对象替换成另外一个。
@Nullable
protected Object applyBeanPostProcessorsBeforeInstantiation(Class<?> beanClass, String beanName) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
Object result = ibp.postProcessBeforeInstantiation(beanClass, beanName);
if (result != null) {
return result;
}
}
}
return null;
}
applyBeanPostProcessorsAfterInitialization初始化
这个主要是前面如果有返回不为空的，就会执行这个来初始化。
@Override
public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)
throws BeansException {
Object result = existingBean;
for (BeanPostProcessor processor : getBeanPostProcessors()) {
Object current = processor.postProcessAfterInitialization(result, beanName);
if (current == null) {
return result;
}
result = current;
}
return result;
}
扩展点实战
我们来试试刚才的扩展点，我想把MyConfig类替换掉。替换成和spring无依赖的一个类：
MyInstantiationAwareBeanPostProcessor扩展类
postProcessBeforeInstantiation方法返回MyBeforeInstantiation对象，然后postProcessAfterInitialization初始化属性age。
@Component
public class MyInstantiationAwareBeanPostProcessor implements InstantiationAwareBeanPostProcessor
{
@Override
public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException {
return new MyBeforeInstantiation();
}
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
MyBeforeInstantiation myBeforeInstantiation=(MyBeforeInstantiation)bean;
myBeforeInstantiation.age=10;
return null;
}
}
测试代码
@Test
public void BeanDefinitionRegistryPostProcessorTest0() throws Exception {
AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext();
applicationContext.register(MyConfig.class);
applicationContext.refresh();
MyBeforeInstantiation myBeforeInstantiation = applicationContext.getBean(MyBeforeInstantiation.class);
System.out.println(myBeforeInstantiation.age);
在MyConfig实例化之前替换：
之后就初始化age：
最后单例就变这样：
取出来了：
好了，今天就到这里了，希望对学习理解有帮助，大神看见勿喷，仅为自己的学习理解，能力有限，请多包涵。