自写Autowired注解

package com.ntan520.reflect;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

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

package com.ntan520.reflect;

public class PersonService {
}

package com.ntan520.reflect;

public class PersonController {

    @Autowired
    private PersonService personService;

    public PersonService getPersonService() {
        return personService;
    }
}

package com.ntan520.reflect;

import java.lang.reflect.Field;

public class TestAutowired {

    public static void main(String[] args) throws Exception {
        PersonController personController = new PersonController();
        Class<? extends PersonController> clazz = personController.getClass();
        //获取所有的属性值
        Field[] declaredFields = clazz.getDeclaredFields();

        for (Field field : declaredFields) {
            String fieldName = field.getName();
            System.out.println("fieldName:" + fieldName);
            Autowired annotation = field.getAnnotation(Autowired.class);

            //判断当前属性是否有Autowired这个注解
            if (null != annotation) {
                //设置属性可以访问
                field.setAccessible(true);
                //获取属性类型
                Class<?> type = field.getType();
                //通过属性类型创建实例
                Object o = type.newInstance();
                //把创建好的实例对象设置到controller上
                field.set(personController, o);
            }
        }

        System.out.println(personController.getPersonService());
    }
}

// 打印结果
fieldName:personService
com.ntan520.reflect.PersonService@63947c6b