1. 优秀源码点

1.1 给一个对象设置属性

ReflectUtil.setFieldValue(bean, fieldNameOrIndex, value);

1.2 先instanceOf 再强转

if (value instanceof BeanReference) {
    // A 依赖 B，获取 B 的实例化
    BeanReference beanReference = (BeanReference) value;
    value = getBean(beanReference.getBeanName());
}

1.3 泛型定义一个接口

public interface BeanFactory {

   Object getBean(String name) throws BeansException;

   Object getBean(String name, Object... args) throws BeansException;

   <T> T getBean(String name, Class<T> requiredType) throws BeansException;

}

1.4 自定义异常

public class BeansException extends RuntimeException {

    public BeansException(String msg) {
        super(msg);
    }

    public BeansException(String msg, Throwable cause) {
        super(msg, cause);
    }

}

1.5 流读取文件

String content = IoUtil.readUtf8(inputStream);

public InputStream getInputStream() throws IOException {
    InputStream is = classLoader.getResourceAsStream(path);
    if (is == null) {
        throw new FileNotFoundException(
                this.path + " cannot be opened because it does not exist");
    }
    return is;
}

1.6 判断beanClass是不是type的子类

type.isAssignableFrom(beanClass)

1.7 注册jvm关闭的钩子

Runtime.getRuntime().addShutdownHook(new Thread(() -> System.out.println("close！")));

2. 源码总结

2.1 源码中重要的接口

定义标记接口
在 Spring 中有特别多类似这样的标记接口的设计方式，它们的存在就像是一种标 签一样，可以方便统一摘取出属于此类接口的实现类，通常会有 instanceof 一起 判断使用
public interface Aware {
}

2.2 源码中重要的map

单例池，一级缓存singletonObjects

public class DefaultSingletonBeanRegistry implements SingletonBeanRegistry {

    private Map<String, Object> singletonObjects = new HashMap<>();
}


bean的定义map beanDefinitionMap 

public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFactory implements BeanDefinitionRegistry, ConfigurableListableBeanFactory {

    private Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>();

}

3. 需要记住的地方

1. AbstractAutowireCapableBeanFactory 的方法createBean

   AbstractBeanFactory的方法getBean

2. AbstractApplicationContext的refresh方法

3. AbstractBeanFactory
private final List<BeanPostProcessor> beanPostProcessors = new ArrayList<BeanPostProcessor>();