极简版Spring IOC

Spring的一大作用就是IOC，让使用者在使用对象的时候不用手动去赋值属性对象，等于说是把控制权从用户交给了spring，所以叫做IOC（Inversion of Control）

自定义一个注解

@Target({ElementType.CONSTRUCTOR, ElementType.METHOD, ElementType.PARAMETER, ElementType.FIELD, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Autoload {
}

定义一个bean对象，其中有一个属性是另外一个对象

public class TestinjectBean {

    @Autoload
    public Car car;

}

public class Car {
    public void run(){
        System.out.println("豪华跑车正在行驶……");
    }
}

定义一个beanfactory,可以根据class获取到bean对象，并且给加了注解的字段自动赋值

public class BeanFactory {
    /**
     * 根据完整的类名返回bean对象
     * */
    public Object getBeanByClass(Class clazz) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
        Object obj = null;
        Constructor constructor = clazz.getDeclaredConstructor(null);
        obj = constructor.newInstance();

        Field[] fields = clazz.getDeclaredFields();
        for(Field field :fields){
            Annotation[] annotations = field.getAnnotations();
            for(Annotation annotation : annotations){

                if(annotation.annotationType().getName().equals("com.chaoxing.springtest.annotation.Autoload")) {
                    if (!field.getType().isPrimitive()) {
                        Class fieldClazz = field.getType();
                        field.set(obj, fieldClazz.newInstance());
                    }
                }
            }
        }

        return obj;
    }
}

示例

    public static void main(String[] args) throws ClassNotFoundException, InvocationTargetException, NoSuchMethodException, InstantiationException, IllegalAccessException {
        BeanFactory factory = new BeanFactory();
        Class clazz = Class.forName("com.chaoxing.springtest.bean.TestinjectBean");
        TestinjectBean bean = (TestinjectBean) factory.getBeanByClass(clazz);
        bean.car.run();
    }

　整个代码流程为实现最简单的依赖注入流程，不考虑任何异常，旨在加深理解spring IOC的基本思路

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