Spring Boot 自动装配原理及 Starter 实现原理解析

@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 {
	@AliasFor(annotation = EnableAutoConfiguration.class)
	Class<?>[] exclude() default {};
	@AliasFor(annotation = EnableAutoConfiguration.class)
	String[] excludeName() default {};
	@AliasFor(annotation = ComponentScan.class, attribute = "basePackages")
	String[] scanBasePackages() default {};
	@AliasFor(annotation = ComponentScan.class, attribute = "basePackageClasses")
	Class<?>[] scanBasePackageClasses() default {};
	@AliasFor(annotation = ComponentScan.class, attribute = "nameGenerator")
	Class<? extends BeanNameGenerator> nameGenerator() default BeanNameGenerator.class;
	@AliasFor(annotation = Configuration.class)
	boolean proxyBeanMethods() default true;
}
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@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Configuration
@Indexed
public @interface SpringBootConfiguration {
    @AliasFor(
        annotation = Configuration.class
    )
    boolean proxyBeanMethods() default true;
}
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@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@AutoConfigurationPackage
@Import(AutoConfigurationImportSelector.class)
public @interface EnableAutoConfiguration {
	String ENABLED_OVERRIDE_PROPERTY = "spring.boot.enableautoconfiguration";
	Class<?>[] exclude() default {};
	String[] excludeName() default {};
}

public class AutoConfigurationImportSelector implements DeferredImportSelector, BeanClassLoaderAware, ResourceLoaderAware, BeanFactoryAware, EnvironmentAware, Ordered {
	@Override
	public String[] selectImports(AnnotationMetadata annotationMetadata) {
		//1.判断自动装配开关是否打开
		if (!isEnabled(annotationMetadata)) {
			return NO_IMPORTS;
		}
		//2.获取所有需要装配的bean
		AutoConfigurationEntry autoConfigurationEntry = getAutoConfigurationEntry(annotationMetadata);
		return StringUtils.toStringArray(autoConfigurationEntry.getConfigurations());
	}
	protected AutoConfigurationEntry getAutoConfigurationEntry(AnnotationMetadata annotationMetadata) {
		//1.再次判断自动装配开关是否打开
		if (!isEnabled(annotationMetadata)) {
			return EMPTY_ENTRY;
		}
		//2.获取EnableAutoConfiguration注解中的 exclude 和 excludeName
		AnnotationAttributes attributes = getAttributes(annotationMetadata);
		//3.获取需要自动装配的所有配置类，读取META-INF/spring.factories
		//(不止读取当前项目中的META-INF文件，所有的依赖中的META-INF文件都会被读取)
		List<String> configurations = getCandidateConfigurations(annotationMetadata, attributes);
		//4.删除重复依赖、过滤 exclude 的依赖
		configurations = removeDuplicates(configurations);
		Set<String> exclusions = getExclusions(annotationMetadata, attributes);
		checkExcludedClasses(configurations, exclusions);
		configurations.removeAll(exclusions);
		configurations = getConfigurationClassFilter().filter(configurations);
		fireAutoConfigurationImportEvents(configurations, exclusions);
		return new AutoConfigurationEntry(configurations, exclusions);
	}
	...
}
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public interface DeferredImportSelector extends ImportSelector {
}
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public interface ImportSelector {
    String[] selectImports(AnnotationMetadata var1);
}