Spring源码阅读（四）

我们知道，在spring bean生命周期中，我们可以在不同阶段执行处理器或者方法，比如init-method，destroy方法，BeanPostProcessor接口等。那么这些处理器或方法的执行顺序是怎样的，让我们用实际例子来观察。

package com.coshaho.learn.spring;

import java.util.HashMap;
import java.util.Map;

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;

import org.springframework.beans.MutablePropertyValues;
import org.springframework.beans.factory.BeanNameAware;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.annotation.AnnotatedGenericBeanDefinition;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.beans.factory.support.DefaultListableBeanFactory;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.DependsOn;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.stereotype.Component;

/**
 *
 * ASpringProcessor.java Create on 2017年10月17日 下午10:06:35
 *
 * 类功能说明: Spring处理器执行顺序
 *
 * Copyright: Copyright(c) 2013
 * Company: COSHAHO
 * @Version 1.0
 * @Author coshaho
 */
@Component("springProcessor")
@DependsOn("dependsBean")
@ComponentScan("com.coshaho.learn.spring")
public class ASpringProcessor implements InitializingBean, DisposableBean, BeanNameAware
{
    @Autowired
    public BAutowiredBean autowiredBean;

    public ASpringProcessor()
    {
        System.out.println("SpringProcessor construct. x is " + x + ".");
    }

    // BeanNameAware
    public void setBeanName(String name)
    {
        System.out.println("Call BeanNameAware setBeanName, name is " + name + ", x is " + x + ".");
    }

    // DisposableBean
    public void destroy() throws Exception
    {
        System.out.println("Call DisposableBean destroy.");
    }

    // InitializingBean
    public void afterPropertiesSet() throws Exception
    {
        System.out.println("Call InitializingBean afterPropertiesSet.");
    }

    @PostConstruct
    public void postConstruct()
    {
        System.out.println("Call postConstruct method.");
    }

    @PreDestroy
    public void preDestroy()
    {
        System.out.println("Call preDestroy method.");
    }

    public void initMethod()
    {
        System.out.println("Call manually initMethod.");
    }

    public void destroyMethod()
    {
        System.out.println("Call manually destroyMethod.");
    }

    public void sayHello()
    {
        System.out.println("Hello, Spring.");
    }

    @Value("cauchy")
    private String x;
    public void setX(String x)
    {
        this.x = x;
    }

    public static void main(String[] args) throws Exception
    {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath:spring.xml");
        ASpringProcessor springBean = (ASpringProcessor)context.getBean("springProcessor");
        springBean.sayHello();
        context.close();

        System.out.println();

        // 创建一个BeanFactory
        DefaultListableBeanFactory factory = new DefaultListableBeanFactory();
        factory.addBeanPostProcessor(new EBeanPostProcessor());

        // 构造一个BeanDefinition
        AnnotatedGenericBeanDefinition beanDefinition=new AnnotatedGenericBeanDefinition(ASpringProcessor.class);
        beanDefinition.setInitMethodName("initMethod");
        beanDefinition.setDestroyMethodName("destroyMethod");

        // 设置这个bean的属性
        Map<String, Object> map = new HashMap<String, Object>();
        map.put("x", "coshaho");
        beanDefinition.setPropertyValues(new MutablePropertyValues(map));

        // 注册BeanDefinition
        factory.registerBeanDefinition("springProcessor", beanDefinition);

        // 执行获取和销毁bean的方法
        factory.getBean("springProcessor");
        factory.destroySingleton("springProcessor");
    }
}

package com.coshaho.learn.spring;

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

class EBeanPostProcessor implements BeanPostProcessor
{
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException
    {
        System.out.println("MyBeanPostProcessor postProcessBeforeInitialization.");
        return bean;
    }

    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException
    {
        System.out.println("MyBeanPostProcessor postProcessAfterInitialization.");
        return bean;
    }
} 

package com.coshaho.learn.spring;

import org.springframework.stereotype.Service;

@Service
public class BAutowiredBean
{
    public BAutowiredBean()
    {
        System.out.println("AutowiredBean construct.");
    }

}

package com.coshaho.learn.spring;

import org.springframework.stereotype.Service;

@Service("dependsBean")
public class CDependsBean
{
    public CDependsBean()
    {
        System.out.println("DependsBean construct.");
    }

}

执行结果

Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@7cef4e59: startup date [Tue Oct 17 18:18:23 GMT+08:00 2017]; root of context hierarchy
Loading XML bean definitions from class path resource [spring.xml]
DependsBean construct.
SpringProcessor construct. x is null.
AutowiredBean construct.
Call BeanNameAware setBeanName, name is springProcessor, x is cauchy.
Call postConstruct method.
Call InitializingBean afterPropertiesSet.
Hello, Spring.
Closing org.springframework.context.support.ClassPathXmlApplicationContext@7cef4e59: startup date [Tue Oct 17 18:18:23 GMT+08:00 2017]; root of context hierarchy
Call preDestroy method.
Call DisposableBean destroy.

SpringProcessor construct. x is null.
Call BeanNameAware setBeanName, name is springProcessor, x is coshaho.
MyBeanPostProcessor postProcessBeforeInitialization.
Call InitializingBean afterPropertiesSet.
Call manually initMethod.
MyBeanPostProcessor postProcessAfterInitialization.
Call DisposableBean destroy.
Call manually destroyMethod.

可以看出来，spring bean加载顺序如下

1. 初始化depends bean；

2. 执行bean构造方法；

3. 初始化依赖注入bean；

4. 其他属性赋值；

5. 执行BeanNameAware接口的setBeanName方法；

6. 执行BeanPostProcessor接口postProcessBeforeInitialization方法；

7. 执行@PostConstruct注解方法；

8. 执行InitializingBean接口的afterPropertiesSet方法；

9. 执行init-method方法；

10. 执行BeanPostProcessor接口postProcessAfterInitialization方法；

11. 执行@PreDestroy注解方法；

12. 执行DisposableBean接口的destroy方法；

13. 执行destroy-method方法。