spring有关bean的加载问题

一、好言

掏心掏肺的对一个人好，要么得到一生的知己，要么换来一生的教训。

二、背景

最近离职在交接，所以有时间来在看看spring的一些加载及周期问题，自己写代码测试，看看源码之类的，最近用了ApplicationContextAware，BeanPostProcessor，慢慢熟悉用法，然后在跟源码看了。下面是一些示例。

三、代码示例

3.1 bean加载顺序

1. 实例化;
2. 设置属性值;
3. 如果实现了BeanNameAware接口,调用setBeanName设置Bean的ID或者Name;
4. 如果实现BeanFactoryAware接口,调用setBeanFactory 设置BeanFactory;
5. 如果实现ApplicationContextAware,调用setApplicationContext设置ApplicationContext
6. 调用BeanPostProcessor的预先初始化方法;
7. 调用InitializingBean的afterPropertiesSet()方法;
8. 调用定制init-method方法；
9. 调用BeanPostProcessor的后初始化方法;

摘自网上

3.2 bean的初始化

package com.mouse.moon.spring.bean;
import org.springframework.beans.factory.InitializingBean;
/**
 * Created by Mahone Wu on 2017/3/17.
 */
public class Man implements InitializingBean {


    private WoMan woMan;

    public Man(){
        System.out.println("初始化  man");
    }

    public void setWoMan(WoMan woMan){
        System.out.println("setWoMan");
        this.woMan = woMan;
    }

    public void init(){
        System.out.println("init");
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        System.out.println("afterPropertiesSet");
    }

}

package com.mouse.moon.spring.bean;
/**
 * Created by Mahone Wu on 2017/3/17.
 */
public class WoMan {
    public WoMan(){
        System.out.println("init... woman类");
    }

    /**说点啥了*/
    public String say(String str){
        return  str;
    }
}

package com.mouse.moon.spring.bean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.FileSystemXmlApplicationContext;
/**
 * Created by Mahone Wu on 2017/3/17.
 */
public class Main {
    public static void main(String[] args) {
        ApplicationContext context = new FileSystemXmlApplicationContext("classpath:/test/spring.xml");
        Man man = (Man)context.getBean("man");
    }
}

打印日志如下：

初始化  man
.17:42:12.463 DEBUG [main] org.springframework.beans.factory.support.DefaultListableBeanFactory[529] - Eagerly caching bean 'man' to allow for resolving potential circular references
.17:42:12.465 DEBUG [main] org.springframework.beans.factory.support.DefaultListableBeanFactory[221] - Creating shared instance of singleton bean 'woMan'
.17:42:12.465 DEBUG [main] org.springframework.beans.factory.support.DefaultListableBeanFactory[448] - Creating instance of bean 'woMan'
init... woman类
.17:42:12.465 DEBUG [main] org.springframework.beans.factory.support.DefaultListableBeanFactory[529] - Eagerly caching bean 'woMan' to allow for resolving potential circular references
.17:42:12.466 DEBUG [main] org.springframework.beans.factory.support.DefaultListableBeanFactory[484] - Finished creating instance of bean 'woMan'
setWoMan
.17:42:12.521 DEBUG [main] org.springframework.beans.factory.support.DefaultListableBeanFactory[1620] - Invoking afterPropertiesSet() on bean with name 'man'
afterPropertiesSet
.17:42:12.522 DEBUG [main] org.springframework.beans.factory.support.DefaultListableBeanFactory[1678] - Invoking init method  'init' on bean with name 'man'
init

执行的顺序：
构造方法
set方法
afterPropertiesSet
init-method方法配置

如果加上@PostConstruct，则需要在xml里面加上如下配置

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/context
       http://www.springframework.org/schema/context/spring-context.xsd">
       <context:annotation-config/>
       <bean id="man" class="com.mouse.moon.spring.bean.Man" init-method="init">
              <property name="woMan" ref="woMan"></property>
       </bean>
       <bean id="woMan" class="com.mouse.moon.spring.bean.WoMan"></bean>
</beans>

<context:annotationconfig />将隐式地向Spring容器注册AutowiredAnnotationBeanPostProcessor、 CommonAnnotationBeanPostProcessor、 PersistenceAnnotationBeanPostProcessor以及 RequiredAnnotationBeanPostProcessor这4个BeanPostProcessor。