源码学习系列之SpringBoot自动配置源码学习（篇一）

ok，本博客尝试跟一下Springboot的自动配置源码，做一下笔记记录，自动配置是Springboot的一个很关键的特性，也容易被忽略的属性，因为这个属性被包括在@SpringBootApplication注解里，所以不去跟一下源码都不知道还有这个属性，ps：本博客源码基于SpringBoot1.5.7版本

@SpringBootApplication

ok，跟一下@SpringBootApplication，发现@SpringBootApplication其实是一个复合的注解，由很多注解构成，@EnableAutoConfiguration其实只是其一部分，@EnableAutoConfiguration就是开启自动配置的注解

// // Source code recreated from a .class file by IntelliJ IDEA // (powered by Fernflower decompiler) //  package org.springframework.boot.autoconfigure;  import java.lang.annotation.Documented; import java.lang.annotation.ElementType; import java.lang.annotation.Inherited; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.annotation.Target; import org.springframework.boot.SpringBootConfiguration; import org.springframework.boot.context.TypeExcludeFilter; import org.springframework.context.annotation.ComponentScan; import org.springframework.context.annotation.FilterType; import org.springframework.context.annotation.ComponentScan.Filter; import org.springframework.core.annotation.AliasFor;  @Target({ElementType.TYPE}) @Retention(RetentionPolicy.RUNTIME) @Documented @Inherited @SpringBootConfiguration  @EnableAutoConfiguration //自动配置注解 @ComponentScan(     excludeFilters = {@Filter(     type = FilterType.CUSTOM,     classes = {TypeExcludeFilter.class} ), @Filter(     type = FilterType.CUSTOM,     classes = {AutoConfigurationExcludeFilter.class} )} ) public @interface SpringBootApplication {     ....     Class<?>[] scanBasePackageClasses() default {}; } 

@EnableAutoConfiguration

点进@EnableAutoConfiguration，比较重要的列出来：

• @AutoConfigurationPackage
• @Import({EnableAutoConfigurationImportSelector.class})

package org.springframework.boot.autoconfigure;  import java.lang.annotation.Documented; import java.lang.annotation.ElementType; import java.lang.annotation.Inherited; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.annotation.Target; import org.springframework.context.annotation.Import;  @Target({ElementType.TYPE}) @Retention(RetentionPolicy.RUNTIME) @Documented @Inherited @AutoConfigurationPackage @Import({EnableAutoConfigurationImportSelector.class}) public @interface EnableAutoConfiguration {     String ENABLED_OVERRIDE_PROPERTY = "spring.boot.enableautoconfiguration";      Class<?>[] exclude() default {};      String[] excludeName() default {}; }

@AutoConfigurationPackage

先看@AutoConfigurationPackage源码，这个注解是开启自动配置包的，关注点在@Import({Registrar.class})，核心在Registrar类

备注：@import注解是Spring的底层注解，作用是导入一个组件到容器里

 package org.springframework.boot.autoconfigure;  import java.lang.annotation.Documented; import java.lang.annotation.El