【小家Spring】一文读懂Spring中的BeanFactory和FactoryBean（以及它和ObjectFactory的区别）的区别(上)

public interface BeanFactory {
  // 该常量用来区分是获取FactoryBean还是FactoryBean的createBean创建的实例.如果&开始则获取FactoryBean;否则获取createBean创建的实例.
  // 备注，此常量课时定义在BeanFactory里面的哟，因为它属于Bean工厂的处理机制~~~
  String FACTORY_BEAN_PREFIX = "&";
  //==========获取bean,这边可以实现单例,原型
  Object getBean(String name) throws BeansException;
  <T> T getBean(String name, Class<T> requiredType) throws BeansException;
  Object getBean(String name, Object... args) throws BeansException;
  <T> T getBean(Class<T> requiredType) throws BeansException;
  <T> T getBean(Class<T> requiredType, Object... args) throws BeansException;
  // ======== 
  <T> ObjectProvider<T> getBeanProvider(Class<T> requiredType);
  <T> ObjectProvider<T> getBeanProvider(ResolvableType requiredType);
  //判断是否包含Bean。此处有个陷阱：这边不管类是否抽象类,懒加载,是否在容器范围内,只要符合都返回true,所以这边true,**不一定能从getBean获取实例**
  boolean containsBean(String name);
   // =============是否是单例 类型匹配的一些判断
  boolean isSingleton(String name) throws NoSuchBeanDefinitionException;
  boolean isPrototype(String name) throws NoSuchBeanDefinitionException;
  boolean isTypeMatch(String name, ResolvableType typeToMatch) throws NoSuchBeanDefinitionException;
  boolean isTypeMatch(String name, Class<?> typeToMatch) throws NoSuchBeanDefinitionException;
  // 获取Bean的类型、别名等等
  @Nullable
  Class<?> getType(String name) throws NoSuchBeanDefinitionException;
  String[] getAliases(String name);
}

Resource resource = new FileSystemResource("beans.xml");
BeanFactory factory = new XmlBeanFactory(resource);

ClassPathResource resource = new ClassPathResource("beans.xml");
BeanFactory factory = new XmlBeanFactory(resource);

ApplicationContext context = new ClassPathXmlApplicationContext(new String[] {"applicationContext.xml", "applicationContext-part2.xml"});
BeanFactory factory = (BeanFactory) context;

/**
 * 自己实现一个FactoryBean 生产出来的对象的前后都输出一个日志
 * <p>
 * InitializingBean：初始化完成后执行操作
 * DisposableBean：销毁后做出对应操作
 *
 * @author fangshixiang
 * @description //
 * @date 2018/12/18 15:19
 */
public class MyFactoryBean implements FactoryBean<Object> {
       private static final Logger logger = LoggerFactory.getLogger(MyFactoryBean.class);
    private Class<?> interfaceClazz; //实现的接口的全类名
    private Object target; //该接口的实现类
    private Object proxyObj;
    public MyFactoryBean(Class<?> interfaceClazz, Object target) {
        this.interfaceClazz = interfaceClazz;
        this.target = target;
        this.proxyObj = Proxy.newProxyInstance(
                this.getClass().getClassLoader(),
                new Class[]{interfaceClazz}, //默认必须实现这个接口
                (proxy, method, args) -> {
                    logger.debug("invoke method......" + method.getName());
                    logger.debug("invoke method before......" + System.currentTimeMillis());
                    Object result = method.invoke(target, args);
                    logger.debug("invoke method after......" + System.currentTimeMillis());
                    return result;
                });
    }
    @Override
    public Object getObject() {
        return proxyObj; //返回这个代理对象 而不是new直接new出来的对象
    }
    @Override
    public Class<?> getObjectType() {
        return proxyObj == null ? Object.class : proxyObj.getClass();
    }
    @Override
    public boolean isSingleton() {
        return true;
    }
}