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  • Springtboot源码(一)

    一、简单构建一个springboot项目

    @SpringBootApplication
    public class SpringbootApplication {
        public static void main(String[] args) {
            SpringApplication.run(SpringbootApplication.class, args);
        }
    }

      只要启动上述代码,就能启动一个基本的springboot项目,springboot启动的核心就在于  @SpringBootApplication 注解以及 SpringApplication.run(SpringbootApplication.class, args); 

    下面也将围绕这两个方法进行讲解。

    二、@SpringBootApplication 原理

    @Target(ElementType.TYPE)
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    @Inherited
    @SpringBootConfiguration
    @EnableAutoConfiguration
    @ComponentScan(excludeFilters = { @Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class),
            @Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) })
    public @interface SpringBootApplication {

      源码如上,可以看到@SpringBootApplication 是个符合注解,其中重点是

    • @ComponentScan(excludeFilters = { @Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class), @Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) })

    • @EnableAutoConfiguration

      2.1  第一个注解@ComponentScan

    @ComponentScan(excludeFilters = { @Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class), @Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) })  

      扫码根路径下所有@Controller @Service @Respository @componet 并注入到spring容器中,然后排除TypeExcludeFilter和AutoConfigurationExcludeFilter中定义的bean。

      2.2  第二个注解:@EnableAutoConfiguration (核心)

    @Target(ElementType.TYPE)
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    @Inherited
    @AutoConfigurationPackage
    @Import(AutoConfigurationImportSelector.class)
    public @interface EnableAutoConfiguration {

      查看源码可知,@EnableAutoConfiguration也是一个符合注解,其中

    • @Import(AutoConfigurationImportSelector.class)
    • @AutoConfigurationPackage

        2.2.1  @Import(AutoConfigurationImportSelector.class)

       @import注解用于将bean导入到spring容器中,具体哪些bean需要导入容器则查看AutoConfigurationImportSelector 源码,查看AutoConfigurationImportSelector 的

     selectImports 方法,该方法加载META-INF/spring.factories下EnableAutoConfiguration的类(常用的JdbcTemplateAutoConfiguration等自动注解类)加载到容器中,如下图spring.factories

    • @EnableAutoConfiguration
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  • 原文地址:https://www.cnblogs.com/shyroke/p/14618898.html
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