BeanPostProcessor使用

1. BeanPostProcessor簡介

BeanPostProcessor是Spring IOC容器給我們提供的一個擴展接口。接口聲明如下：

public interface BeanPostProcessor {
    //bean初始化方法調用前被調用
    Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException;
    //bean初始化方法調用後被調用
    Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException;
}

運行順序

===Spring IOC容器實例化Bean===
===調用BeanPostProcessor的postProcessBeforeInitialization方法===
===調用bean實例的初始化方法===
===調用BeanPostProcessor的postProcessAfterInitialization方法===

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2. BeanPostProcessor實例

/**
 * 後置處理器：初始化前後進行處理工作
 * 將後置處理器加入到容器中
 */
@Component
public class MyBeanPostProcessor implements BeanPostProcessor {

    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        // TODO Auto-generated method stub
        System.out.println("postProcessBeforeInitialization..."+beanName+"=>"+bean);
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        // TODO Auto-generated method stub
        System.out.println("postProcessAfterInitialization..."+beanName+"=>"+bean);
        return bean;
    }

}

3. BeanFactoryPostProcessor簡介

bean工廠的bean屬性處理容器，說通俗一些就是可以管理我們的bean工廠內所有的beandefinition（未實例化）數據，可以隨心所欲的修改屬性。

4. BeanFactoryPostProcessor實例

@Component
public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
        System.out.println("MyBeanFactoryPostProcessor...postProcessBeanFactory...");
        int count = beanFactory.getBeanDefinitionCount();
        String[] names = beanFactory.getBeanDefinitionNames();
        System.out.println("當前BeanFactory中有"+count+" 個Bean");
        System.out.println(Arrays.asList(names));
    }

}

區別：

註冊BeanFactoryPostProcessor的實例，需要重載

void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException;

通過beanFactory可以獲取bean的示例或定義等。同時可以修改bean的屬性，這是和BeanPostProcessor最大的區別。