SpringIOC 容器手写(三)--基于注解创建容器，依赖注入

1. 自定义注解

• 类级别的注解

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface ExtService {
}

• 属性级别的注解

@Target({ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
public @interface ExtAutowired {
}

2. 指定扫描的package，得到包下的class List

具体的实现可以直接参考Spring源码(不重要)

//获取该包名下的class
List<Class<?>> classes = ClassUtil.getClasses(packageName);

3. 找到添加了注解的bean，并把实例存储到map中

 public ConcurrentHashMap<String, Object> findClassExistAnnotation(List<Class<?>> classes) throws IllegalAccessException, InstantiationException, ClassNotFoundException {
        for (Class<?> clazz : classes) {
            ExtService annotation = clazz.getAnnotation(ExtService.class);
            if (annotation != null) {
                String className = clazz.getSimpleName();
                Object obj = newInstance(clazz.getName(), new HashMap<>());
                beans.put(toLowerCaseFirstOne(className), obj);
                continue;
            }
        }
        return beans;
    }

4. 为实例添加依赖注解类

/**
     * 依赖注入
     */
    public void attributeAssign(Object obj) throws IllegalAccessException {
        Field[] fields = obj.getClass().getDeclaredFields();
        for (Field field : fields) {
            ExtAutowired autowired = field.getAnnotation(ExtAutowired.class);
            if (autowired != null) {
                String fieldName = field.getName();
                //获取到依赖注入的bean
                Object bean = beans.get(fieldName);
                if (bean != null) {
                    field.setAccessible(true);
                    field.set(obj, bean);
                }
            }
        }
    }

给bean添加依赖注解

        annotionBeans.entrySet().stream().forEach(entry -> {
            try {
                attributeAssign(entry.getValue());
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
        });