Spring之BeanFactory中Bean的生命周期

<声明：读书总结自《精通Spring 4.x 企业应用开发实战》 作者：陈雄华 林开雄 文建国>

spring中bean实例化的过程主要有四个关键点：

• Bean本身定义的方法，如构造函数，静态代码块，属性设置器等
• Bean级生命周期控制接口的方法，如BeanFactoryAware,BeanNameAware,InitializingBean,DisposableBean
• 容器级生命周期接口方法，如InstantiationAwareBeanPostProcessorAdapter等后处理器
• 工厂后处理器接口方法，如：ConfigurationClassPostProcessor等

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.BeanNameAware;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;

/** * 这里实现Bean级生命周期控制接口：如BeanFactoryAware,BeanNameAware,InitializingBean,DisposableBean * */
public class Car implements BeanFactoryAware,BeanNameAware,InitializingBean,DisposableBean{

    private String brand;
    private String color;
    private int maxSpeed;

    private BeanFactory beanFactory;
    private String beanName;

    //第二：通过 构造函数，实例化bean，当然 静态代码块在构造之前。
    static{
        System.out.println("调用Car的静态代码块");
    }

    public Car(){
        System.out.println("调用Car的构造函数");
    }

    public void introduce(){
        System.out.println("brand:"+brand+";color:"+color+";maxSpeed:"+maxSpeed);
    }

    //第五步：对bean的属性进行设置，
    public void setBrand(String brand){
        this.brand = brand;
        System.out.println("调用Car的setBrand()设置属性");
    }

    //第十四步：如果实现了DisposableBean接口。容器关闭时会调用销毁方法
    @Override
    public void destroy() throws Exception {
        System.out.println("调用DisposableBean.destroy()");
    }

    //第十步：如果bean实现了InitializingBean，会调用afterPropertiesSet方法。
    /* * This method allows the bean instance to perform initialization only * possible when all bean properties have been * set and to throw an exception in the event of misconfiguration. */
    @Override
    public void afterPropertiesSet() throws Exception {
        System.out.println("调用InitializingBean.afterPropertiesSet()");
    }

    //第六步是：调用 BeanNameAware.setBeanName()的方法，将配置文件中的名称设置到Bean中。
    @Override
    public void setBeanName(String beanName) {
        System.out.println("调用BeanNameAware.setBeanName()");
        this.beanName = beanName;
    }

    //第七：如果bean实现了BeanFactoryAware接口，就会调用此方法，将BeanFactory容器设置到bean中；
    //BeanFactoryAware接口方法
    @Override
    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
        System.out.println("调用BeanFactoryAware.setBeanFactory()");
        this.beanFactory = beanFactory;
    }

    //第十一步：如果配置文件对init-method进行了配置，会调用自定义的init方法
    public void myInit(){
        System.out.println("my init()");
    }

    //第十五步：如果在配置文件中定义了destroy-method="myDestroy"，则会调用自定义的销毁方法
    public void myDestroy(){
        System.out.println("my derstroy()");
    }

    public String getColor() {
        return color;
    }

    public void setColor(String color) {
        this.color = color;
    }

    public int getMaxSpeed() {
        return maxSpeed;
    }

    public void setMaxSpeed(int maxSpeed) {
        this.maxSpeed = maxSpeed;
    }

    public String getBrand() {
        return brand;
    }

    public BeanFactory getBeanFactory() {
        return beanFactory;
    }

    public String getBeanName() {
        return beanName;
    }

}

import java.beans.PropertyDescriptor;

import org.springframework.beans.BeansException;
import org.springframework.beans.PropertyValues;
import org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessorAdapter;


/** *@className MyInstantiationAwareBeanPostProcessor *@description ：容器级 生命周期接口，通过继承InstantiationAwareBeanPostProcessorAdapter适配器来进行扩展。 * */
public class MyInstantiationAwareBeanPostProcessor extends InstantiationAwareBeanPostProcessorAdapter{

    /* * 第一：当 调用者通过getBean("xxx")向spring容器请求该bean，如果容器注册了InstantiationAwareBeanPostProcessorAdapter， * 会首先吊用此方法，它发生在bean的实例化之前。 */
    @Override
    public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException {
        if("car".equals(beanName)){
            System.out.println("InstantiationAwareBeanPostProcessor.postProcessBeforeInstantiation()");
        }
        return null;
    }

    /* * 第三步：如果说 容器注册了InstantiationAwareBeanPostProcessorAdapter，实例化bean之后的首先调用postProcessAfterInstantiation方法； * 可以在这里对bean实例进行一些改造。 */
    @Override
    public boolean postProcessAfterInstantiation(Object bean, String beanName) throws BeansException {
        if("car".equals(beanName)){
            System.out.println("InstantiationAwareBeanPostProcessor.postProcessAfterInstantiation() return boolean");
        }
        return true;
    }

    /* * 第四步：如果说 bean配置了属性信息， 容器注册了InstantiationAwareBeanPostProcessorAdapter，就会先调用postProcessPropertyValues方法 * 然后才会去调用bean设置属性的相关方法 */
    @Override
    public PropertyValues postProcessPropertyValues(
            PropertyValues pvs, PropertyDescriptor[] pds, Object bean, String beanName) throws BeansException {
        if("car".equals(beanName)){
            System.out.println("InstantiationAwareBeanPostProcessor.postProcessPropertyValues() ");
        }
        return pvs;
    }

    /* * 第九步：通过第八步的BeanPostProcessor的postProcessBeforeInitialization返回到这里的是一个经过特殊处理的bean * * 对于此方法的作用:Apply this BeanPostProcessor to the given new bean instance before any bean initialization * callbacks (like InitializingBean's afterPropertiesSet or a custom init-method). * The bean will already be populated with property values. * The returned bean instance may be a wrapper around the original. */
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        if("car".equals(beanName)){
            System.out.println("InstantiationAwareBeanPostProcessor.postProcessBeforeInitialization() ----");
        }
        return bean;
    }

    /* * * 第十三步：通过第十二步的BeanPostProcessor的postProcessAfterInitialization返回到这里的是一个经过特殊处理的bean * */
    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        if("car".equals(beanName)){
            System.out.println("InstantiationAwareBeanPostProcessor.postProcessAfterInitialization() ----");
        }
        return bean;
    }
}

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

/** *@className MyBeanPostProcessor *@description ：容器级 生命周期接口，实现 BeanPostProcessor接口； * *BeanPostProcessor有着重要作用，spring的aop、动态代理就是通过它实施的。 * */
public class MyBeanPostProcessor implements BeanPostProcessor{

    /* * *第八步： 如果BeanFactory装配了BeanPostProcessor后处理器，就会调用postProcessBeforeInitialization方法。这里的参数bean就是 *我们要处理的bean实例。beanName就是当前Bean的配置名，这里进行bean特殊处理。 * */
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        if(beanName.equals("car")){
            Car car = (Car) bean;
            if(car.getColor() == null)
                System.out.println("调用BeanPostProcessor的postProcessBeforeInitialization(),color是空，设置为黑色");
            car.setColor("黑色");
        }
        return bean;
    }

    /* * *第十二步：BeanPostProcessor后处理器的postProcessAfterInitialization，可以继续处理bean实例 * */
    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        if(beanName.equals("car")){
            Car car = (Car) bean;
            if(car.getMaxSpeed() > 200)
                System.out.println("调用BeanPostProcessor的postProcessAfterInitialization(),速度调为200");
            car.setMaxSpeed(200);
        }
        return bean;
    }

}

import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.config.ConfigurableBeanFactory;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.DefaultListableBeanFactory;
import org.springframework.beans.factory.xml.XmlBeanDefinitionReader;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;
/** * *@className SpringBeanLifeCycle *@description ：spring bean的生命周期 *@date 2017年5月30日下午7:03:13 * * * 打印出的结果如下： * 第一步：InstantiationAwareBeanPostProcessor.postProcessBeforeInstantiation() 第二步：调用Car的静态代码块 调用Car的构造函数 第三步：InstantiationAwareBeanPostProcessor.postProcessAfterInstantiation() return boolean 第四步：InstantiationAwareBeanPostProcessor.postProcessPropertyValues() 第五步：调用Car的setBrand()设置属性 第六步：调用BeanNameAware.setBeanName() 第七步：调用BeanFactoryAware.setBeanFactory() 第八步：调用BeanPostProcessor的postProcessBeforeInitialization(),color是空，设置为黑色 第九步：InstantiationAwareBeanPostProcessor.postProcessBeforeInitialization() ---- 第十步：调用InitializingBean.afterPropertiesSet() 第十一步：my init() 第十二步：调用BeanPostProcessor的postProcessAfterInitialization(),速度调为200 第十三步：InstantiationAwareBeanPostProcessor.postProcessAfterInitialization() ---- brand:奔驰;color:黑色;maxSpeed:200 car1 == car2:true 第十四步：调用DisposableBean.destroy() 第十五步：my derstroy() */
public class SpringBeanLifeCycle {
    public static void main(String[] args) {
        Resource res = new ClassPathResource("spring/IoC/beanlife/applicationContext.xml");
        BeanFactory bf = new DefaultListableBeanFactory();
        XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader((BeanDefinitionRegistry) bf);

        reader.loadBeanDefinitions(res);

        //在容器中注册 BeanPostProcessor后处理器
        ((ConfigurableBeanFactory)bf).addBeanPostProcessor(new MyBeanPostProcessor());

        //在容器中注册InstantiationAwareBeanPostProcessor后处理器
        ((ConfigurableBeanFactory)bf).addBeanPostProcessor(new MyInstantiationAwareBeanPostProcessor());

        //第一次获取Car，会触发容易实例化Bean，调用bean生命周期的方法
        Car car1 = (Car) bf.getBean("car");
        car1.introduce();
        car1.setColor("粉色");

        //第二次直接从容器缓存池中获取
        Car car2 = (Car) bf.getBean("car");

        //所以   这是同一个实例对象。配置文件改为prototype就会不同了。
        System.out.println("car1 == car2:"+(car1==car2));

        //关闭容器会 调用destroy方法
        ((ConfigurableBeanFactory)bf).destroySingletons();
    }
}

转载于:https://my.oschina.net/kevin1992/blog/913529