面试Spring之IOC原理

你了解Spring IOC么

IOC：控制反转

->Spring Core最核心的部分

->需要先了解依赖注入

DI：设计行李箱

轮子<-------(依赖）底盘<-------(依赖）箱体<-------(依赖）行李箱

上层建筑依赖下层建筑

public class Luggage{

    private Framework framework ;
    Luggage(int size){
        this.framework = new framework (size);
    }
    public void move(){
        // ...相关逻辑
    }
}

public class Framework {

    private Bottom bottom;
    Framework (int size){
        this.bottom = new Bottom (size);
    }
}
public class Bottom{
    private Tire tire;
    Bottom(int size){
        this.tire = new Tire(size);
    }
}
public class Tire{
    private int size;
    Tire(int size){
        this.size = size;
    }
}

int size = 30;
Luggage luggage = new Luggage(size);
luggage.move();

依赖注入

含义：把底层类作为参数传递给上层类，实现上层对下层的“控制”

行李箱<-------(注入）箱体<-------(注入）底盘<-------(注入）轮子

public class Tire{
    private int size;
    Tire(){
        this.size = 20;
    }
}

public class Bottom{
    private Tire tire;
    Bottom(Tire tire){
        this.tire = tire;
    }
}
public class Framework{
    private Bottom bottom;
    Framework(Bottom bottom){
        this.bottom = bottom;
    }
}
public class Luggage{
    private Framework framework;
    Luggage(Framework framework){
        this.framework = framework;
    }
    public void move(){
        // ...相关逻辑
    }
}

int size = 30;
Tire tire = new Tire(size);
Bottom bottom = new Bottom(tire);
Framework framework = new Framework(bottom);
Luggage luggage = new Luggage(framework);
luggage.move();

依赖注入主要有以下的方式

->Setting

->Interface

->Constructor

->Annotation(注解)

依赖倒置原则，IOC，DI，IOC容器的关系

依赖倒置原则：高层模块不应该依赖于底层模块，两者都应该依赖其抽象------->(思路）IoC，离不开依赖注入的支撑，Spring框架基于IoC，提出容器的概念 ，对IoC最重要的就是容器了，容器管理者bean的生命周期，控制着bean的依赖注入 

IOC容器的优势

->避免在各处使用new来创建对象，并且可以做到统一维护

->创建实例的时候不需要了解其中的细节

 

IocC Container "工厂"，我们就像是工厂的客户，查Config，Config，Config，Config。。。，到底了开始往上创建，注入，注入，住入，注入。。。

 

看视频《剑指Java面试》记录下的