Spring核心学习（2）管理Bean的生命周期

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前导：开始学习Spring核心思想，通过一个山寨精简版Spring代码结合学习。

内容：1. 抽象BeanFactory-面向接口更易拓展BeanFactory-面向接口更易拓展。 2. 在AbstractBeanFactory内部初始化Bean。

这里的BeanDefinition相比上一个更加丰富，多了BeanDefinition包含的Bean的Class的信息，这里我们不在注册前就把Bean实例化给BeanDefinition，而是延迟到注册的时候才实例化Bean给BeanDefinition。

BeanDefinition：

package step2.core;public class BeanDefinition {private Object bean;private Class beanClass;private String beanClassName;public BeanDefinition() {}public Object getBean() {return bean;}public void setBean(Object bean) {this.bean = bean;}public Class getBeanClass() {return beanClass;}public void setBeanClass(Class beanClass) {this.beanClass = beanClass;}public String getBeanClassName() {return beanClassName;}public void setBeanClassName(String beanClassName) {this.beanClassName = beanClassName;try {this.beanClass = Class.forName(beanClassName);} catch (ClassNotFoundException e) {e.printStackTrace();}}}

BeanFactory：

public interface BeanFactory {Object getBean(String name);void registerBeanDefinition(String name, BeanDefinition beanDefinition);}

AbstractBeanFactory：

public abstract class AbstractBeanFactory implements BeanFactory{private Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<String, BeanDefinition>();@Overridepublic Object getBean(String name) {return beanDefinitionMap.get(name).getBean();}@Overridepublic void registerBeanDefinition(String name,BeanDefinition beanDefinition) {Object bean = doCreateBean(beanDefinition);beanDefinition.setBean(bean);beanDefinitionMap.put(name, beanDefinition);}/**     * 初始化bean     * @param beanDefinition     * @return     */    protected abstract Object doCreateBean(BeanDefinition beanDefinition);}

AutowireCapableBeanFactory：

public class AutowireCapableBeanFactory extends AbstractBeanFactory{@Overrideprotected Object doCreateBean(BeanDefinition beanDefinition) {try {Object bean = beanDefinition.getBeanClass().newInstance();return bean;} catch (InstantiationException e) {e.printStackTrace();} catch (IllegalAccessException e) {e.printStackTrace();}return null;}}

public class HelloWorldService {    public void helloWorld(){        System.out.println("Hello World! from step2");    }}

public class BeanFactoryTest {@Testpublic void test() {// 1.初始化beanBeanFactory beanFactory = new AutowireCapableBeanFactory();// 2.注入beanBeanDefinition beanDefinition = new BeanDefinition();beanDefinition.setBeanClassName("step2.test.HelloWorldService");beanFactory.registerBeanDefinition("helloWorldService", beanDefinition);// 3.获取beanHelloWorldService helloWorldService = (HelloWorldService)beanFactory.getBean("helloWorldService");helloWorldService.helloWorld();}}

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