看完这篇SpringBoot配置原理,你就自己手写一个吧

╰+攻爆jí腚メ 2023-02-21 11:45 19阅读 0赞

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每天叫醒你的不是闹钟，而是梦想

**01**

**前言**

上一篇推文我们讲了几道SpringBoot面试题,今天我们来继续深入研究SpringBoot自动配置原理

从SpringBoot的启动类入手

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@SpringBootApplication:

昨天已经提过,该注解是SpringBoot的核心注解,其源码由

@SpringBootConfiguration
    @EnableAutoConfiguration
    @ComponentScan

三个注解组成,而我们今天要说的就是@EnableAutoConfiguration注解

该注解的作用就是自动配置注解

进入该注解源码

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从AutoConfigurationImportSelector.class这个类入手,进入源码,上篇推文提过,SpringBoot的自动配置原理就是由@Import注解注入了ImportSelectors接口的实现类AutoConfigurationImportSelector,进入ImportSelectors源码中查看

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**02**

**ImportSelector解释**

对注释翻译(小编英语水平较低,勿喷):

ImportSelector接口可以实现以下几个接口:
    EnvironmentAware
    BeanFactoryAware
    BeanClassLoaderAware
    ResourceLoaderAware
    且上述接口的方法会在ImportSelectors接口的方法调用之前调用

ImportSerlectors接口方法selectImports注释翻译:

选择与返回….

算了还是看有道翻译吧

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猜想 : 该方法可以返回导入类的名称,也就是自动导入类的名称?

OK。继续…….

**03**

**验证猜想**

我们现在返回AutoConfigurationImportSelector类中，顺便在返回值的代码打个断点，验证我们刚刚所分析的，启动

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通过debug我们可以看到AutoConfigurationImportSelector一共自动配置了40个Bean。

而@Import的作用就是为我们自动将Bean对象注入到IOC容器中

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也就是在SpringBoot启动类启动的时候为什么注入了40个Bean对象。

根据上面的讲解，接下来我们通过自己手写一个SpringBoot自动配置类来对Bean对象实现自动注入到IOC容器。

**04**

**实践**

步骤：

1.       需要注入到IOC容器的Bean对象

2.       需要一个启动类来启动SpringApplication

3.       启动类需要使用@Import注解来自动注入Bean对象到IOC容器。

1. Bean对象

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2. 启动类与@Import注解

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3.Console(已经创建了对象,并将Bean对象注入到IOC容器中)

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看完懂了?会了?评论给个666吧,哈哈哈!!!

谢谢阅读

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