springboot自动装配

装载谁

@SpringBootApplication 

    @SpringBootConfiguration，@EnableAutoConfiguration，@ComponentScan

@EnableAutoConfiguration开启自动装配

    在classpath下找到all配置的bean进行装配，据若干conditional定制规则初始化

@Import(EnableAutoConfigurationImportSelector.class)1.5中过时，查看父类AutoConfigurationImportSelector

public class AutoConfigurationImportSelector
        implements DeferredImportSelector, BeanClassLoaderAware, ResourceLoaderAware,
        BeanFactoryAware, EnvironmentAware, Ordere

首先实现了DeferredImportSelector接口，继承importSelector：接口上有很多书名，大家去看源码吧，deferred延迟的意思，该类延期导入、所有configuration都处理过后才执行

public interface ImportSelector {

    /**
     * Select and return the names of which class(es) should be imported based on
     * the {@link AnnotationMetadata} of the importing @{@link Configuration} class.
     */
    String[] selectImports(AnnotationMetadata importingClassMetadata);

}

 

 

在AutoConfigurationImportSelector中实现方法为：简单说一下主体方法

meta-inf/spring-autoconfigure-metadata.properties读取元数据及相关属性，调用getCandidateConfigurations读取meta-inf/spring.factories下的enableAutoConfiguration配置，排除过滤，得到相应装配的类，最后让配置

@Override
    public String[] selectImports(AnnotationMetadata annotationMetadata) {
        //是否自动装配，不是返回
        if (!isEnabled(annotationMetadata)) {
            return NO_IMPORTS;
        }
        try {
            //从META-INF/spring-autoconfigure-metadata.properties读取元数据与元数据的相关属性
            AutoConfigurationMetadata autoConfigurationMetadata = AutoConfigurationMetadataLoader
                    .loadMetadata(this.beanClassLoader);

            AnnotationAttributes attributes = getAttributes(annotationMetadata);

            //借助SpringFactoryiesLoader读取META-INF/spring.factories下的EnableAutoConfiguration的配置
            List configurations = getCandidateConfigurations(annotationMetadata,
                    attributes);

            //排除 与过滤
            configurations = removeDuplicates(configurations);
            configurations = sort(configurations, autoConfigurationMetadata);
            Set exclusions = getExclusions(annotationMetadata, attributes);
            checkExcludedClasses(configurations, exclusions);
            configurations.removeAll(exclusions);
            configurations = filter(configurations, autoConfigurationMetadata);

            //所有配置在META-INF/spring.factories下的AutoConfigurationImportListener执行AutoConfigurationImportEvent事件fireAutoConfigurationImportEvents(configurations, exclusions);
            return configurations.toArray(new String[configurations.size()]);

        }catch (IOException ex) {
            throw new IllegalStateException(ex);
        }
    }

 

何时进行自动装配

1、AbstractApplicationContext的refresh方法(这个方法真的是博大精深)字字玑珠，我们先把眼光移步到：

// Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory);

 处理BeanFactoryPostProcessor，

PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());

//看过源码你会知道，BeanFactoryPostProcessor是一个函数式接口
public List getBeanFactoryPostProcessors() {
		return this.beanFactoryPostProcessors;
	}

 

 

ConfigurationClassPostProcessor 这个类主要是处理@Configuration，我要说一看就知道是不是有些不讲道理，debug一下就知道了，实现了BeanDefinitionRegistryPostProcessor，实现了

public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) 

解析了每一个@ConfigurationClass类ConfigurationClassParser