IOC初始化和互相引用解决

羔羊 — Wed, 10 Nov 2010 08:27:00 GMT

摘要: 观察IOC中容器初始化某个Bean顺序，现先一个JAVABean类，看看控制台输出：package com.google.aop.exception.ioc; import org.springframework.beans.BeansException; import org.springframework.beans.factory.BeanFactory... 阅读全文

羔羊 2010-11-10 16:27 发表评论

IOC监管Bean

羔羊 — Wed, 03 Nov 2010 09:04:00 GMT

1.InitializingBean接口，在初始化Bean时容器会调用前者的afterPropertiesSet()方法

2.DisposableBean接口，在析构Bean时容器会调用destroy()方法

3.BeanFactoryAware接口，当它被BeanFactory创建后，它会拥有一个指向创建它的BeanFactory的引用

4.BeanPostProcessor接口，这个接口两个方法，postProcessBeforeInitialization(Object bean, String beanName)和postProcessAfterInitialization(Object bean, String beanName) 在其他Bean构造前后执行

5.BeanFactoryPostProcessor接口，Spring IoC容器允许BeanFactoryPostProcessor在容器实际实例化任何其它的bean之前读取配置元数据，并有可能修改它

package com.google.springioctest;

import org.springframework.beans.BeansException;

import org.springframework.beans.factory.BeanFactory;

import org.springframework.beans.factory.BeanFactoryAware;

import org.springframework.beans.factory.DisposableBean;

import org.springframework.beans.factory.InitializingBean;

import org.springframework.beans.factory.config.BeanFactoryPostProcessor;

import org.springframework.beans.factory.config.BeanPostProcessor;

import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;

public class A implements BeanPostProcessor, InitializingBean,

BeanFactoryAware, BeanFactoryPostProcessor,DisposableBean {

public A() {

System.out.println("Class A");

}

private void init(){

System.out.println("Class A init");

}

@Override

public void afterPropertiesSet() throws Exception {

// TODO Auto-generated method stub

System.out.println("Class A afterPropertiesSet()");

}

@Override

public void destroy() throws Exception {

System.out.println("Class A destroy()");

}

@Override

public void setBeanFactory(BeanFactory beanFactory) throws BeansException {

// TODO Auto-generated method stub

System.out.println("Class A setBeanFactory()");

}

@Override

public Object postProcessAfterInitialization(Object bean, String beanName)

throws BeansException {

System.out.println("Class A postProcessAfterInitialization");

return null;

}

@Override

public Object postProcessBeforeInitialization(Object bean, String beanName)

throws BeansException {

// TODO Auto-generated method stub

System.out.println("Class A postProcessBeforeInitialization");

return null;

}

@Override

public void postProcessBeanFactory(

ConfigurableListableBeanFactory beanFactory) throws BeansException {

// TODO Auto-generated method stub

System.out.println("Class A postProcessBeanFactory");

}

执行结果：

Class A

Class A setBeanFactory()

Class A afterPropertiesSet()

Class A init

Class A postProcessBeanFactory

创建一个B类，由A来监管B类，B实现 InitializingBean,BeanFactoryAware,BeanFactoryPostProcessor

package com.google.springioctest;

import org.springframework.beans.BeansException;

import org.springframework.beans.factory.BeanFactory;

import org.springframework.beans.factory.BeanFactoryAware;

import org.springframework.beans.factory.DisposableBean;

import org.springframework.beans.factory.InitializingBean;

import org.springframework.beans.factory.config.BeanFactoryPostProcessor;

import org.springframework.beans.factory.config.BeanPostProcessor;

import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;

public class B implements InitializingBean, BeanFactoryAware,

BeanFactoryPostProcessor {

public B() {

System.out.println("Class B");

}

public void init() {

System.out.println("Class B init");

}

@Override

public void afterPropertiesSet() throws Exception {

System.out.println("Class B afterPropertiesSet");

}

@Override

public void setBeanFactory(BeanFactory beanFactory) throws BeansException {

System.out.println("Class B beanFactory");

}

@Override

public void postProcessBeanFactory(

ConfigurableListableBeanFactory beanFactory) throws BeansException {

// TODO Auto-generated method stub

System.out.println("Class B postProcessBeanFactory");

}

执行结果：

Class A

Class A setBeanFactory()

Class A afterPropertiesSet()

Class A init

Class B

Class B beanFactory

Class B afterPropertiesSet

Class B init

Class A postProcessBeanFactory

Class B postProcessBeanFactory

可以看出A并没有监管B类，也就是没调用BeanPostProcessor这个接口的2个方法

再来去掉B上的BeanFactoryPostProcessor接口

package com.google.springioctest;

import org.springframework.beans.BeansException;

import org.springframework.beans.factory.BeanFactory;

import org.springframework.beans.factory.BeanFactoryAware;

import org.springframework.beans.factory.DisposableBean;

import org.springframework.beans.factory.InitializingBean;

import org.springframework.beans.factory.config.BeanFactoryPostProcessor;

import org.springframework.beans.factory.config.BeanPostProcessor;

import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;

public class B implements InitializingBean,

BeanFactoryAware{

public B() {

System.out.println("Class B");

}

public void init() {

System.out.println("Class B init");

}

@Override

public void afterPropertiesSet() throws Exception {

System.out.println("Class B afterPropertiesSet");

}

@Override

public void setBeanFactory(BeanFactory beanFactory) throws BeansException {

System.out.println("Class B beanFactory");

}

public void postProcessBeanFactory(

ConfigurableListableBeanFactory beanFactory) throws BeansException {

// TODO Auto-generated method stub

System.out.println("Class B postProcessBeanFactory");

}

执行输出：Class A

Class A setBeanFactory()

Class A afterPropertiesSet()

Class A init

Class A postProcessBeanFactory

2010-11-3 21:33:31 org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons

信息: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@8916a2: defining beans [A,B]; root of factory hierarchy

Class B

Class B beanFactory

Class A postProcessBeforeInitialization

2010-11-3 21:33:31 org.springframework.beans.factory.support.DefaultSingletonBeanRegistry destroySingletons

信息: Destroying singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@8916a2: defining beans [A,B]; root of factory hierarchy

Class A destroy()

Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'B' defined in class path resource [icoContext.xml]: Invocation of init method failed; nested exception is java.lang.NullPointerException

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1338)

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:473)

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409)

at java.security.AccessController.doPrivileged(Native Method)

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380)

at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264)

at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)

at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261)

at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185)

at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164)

at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:429)

at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:728)

at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:380)

at org.springframework.context.support.ClassPathXmlApplicationContext.(ClassPathXmlApplicationContext.java:139)

at org.springframework.context.support.ClassPathXmlApplicationContext.(ClassPathXmlApplicationContext.java:83)

at com.google.springioctest.Test.main(Test.java:8)

Caused by: java.lang.NullPointerException

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeCustomInitMethod(AbstractAutowireCapableBeanFactory.java:1393)

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1375)

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1335)

... 15 more

抛异常了。。。。。

原因是A类里的postProcessBeforeInitialization，postProcessAfterInitialization2个方法没有返回bean,修改下

执行输出：

Class A

Class A setBeanFactory()

Class A afterPropertiesSet()

Class A init

Class A postProcessBeanFactory

2010-11-3 21:37:10 org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons

信息: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@1193779: defining beans [A,B]; root of factory hierarchy

Class B

Class B beanFactory

Class A postProcessBeforeInitialization

Class B afterPropertiesSet

Class B init

Class A postProcessAfterInitialization

在B类被初始化之后，也就是调用afterPropertiesSet之前那段时间，属性初始化完成后，进行了回调，控制B类

注意:在写被监控的Bean的时候，不能实现BeanFactoryPostProcessor这个接口,没看源码，其实也不知道是什么原因，哈哈，只能硬记了

羔羊 2010-11-03 17:04 发表评论

BlogJava-yuyee-随笔分类-IOC

IOC初始化和互相引用解决

IOC监管Bean