Spring boot容器导入组件

你的名字 2022-05-15 05:26 194阅读 0赞

### @Import ###

向容器中，导入组件

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

### EnableAutoConfigurationImportSelector.class ###

点击，进入  
自动配置导包选择器

@Deprecated
    public class EnableAutoConfigurationImportSelector extends AutoConfigurationImportSelector {

### AutoConfigurationImportSelector ###

点击，进入

public String[] selectImports(AnnotationMetadata annotationMetadata) {
        if(!this.isEnabled(annotationMetadata)) {
            return NO_IMPORTS;
        } else {
            try {
                AutoConfigurationMetadata autoConfigurationMetadata = AutoConfigurationMetadataLoader.loadMetadata(this.beanClassLoader);
                AnnotationAttributes attributes = this.getAttributes(annotationMetadata);
                List<String> configurations = this.getCandidateConfigurations(annotationMetadata, attributes);
                configurations = this.removeDuplicates(configurations);
                configurations = this.sort(configurations, autoConfigurationMetadata);
                Set<String> exclusions = this.getExclusions(annotationMetadata, attributes);
                this.checkExcludedClasses(configurations, exclusions);
                configurations.removeAll(exclusions);
                configurations = this.filter(configurations, autoConfigurationMetadata);
                this.fireAutoConfigurationImportEvents(configurations, exclusions);
                return (String[])configurations.toArray(new String[configurations.size()]);
            } catch (IOException var6) {
                throw new IllegalStateException(var6);
            }
        }
    }

### selectImports ###

方法，将所有需要导入的组件，以全类名的方式返回  
这些组件就会被添加到容器中

### Configurations ###

容器，需要导入的组件  
给容器中导入非常多的自动配置类xxxAutoConfiguration  
就是，给容器中导入这个场景需要的所有组件，并配置好这些组件  
有了自动配置类，免去了我们手动编写配置注入功能组件等的工作

getCandidateConfigurations(annotationMetadata, attributes)
    protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) {
        List<String> configurations = SpringFactoriesLoader.loadFactoryNames(this.getSpringFactoriesLoaderFactoryClass(), this.getBeanClassLoader());
        Assert.notEmpty(configurations, "No auto configuration classes found in META-INF/spring.factories. If you are using a custom packaging, make sure that file is correct.");
        return configurations;
    }
    SpringFactoriesLoader.loadFactoryNames(this.getSpringFactoriesLoaderFactoryClass(), this.getBeanClassLoader());

### 配置文件位置 ###

![这里写图片描述][70]

### 文件内容 ###

![这里写图片描述][70 1]  
Spring Boot  
在启动的时候，从类路径下的META-INF/spring.factories中  
获取EnableAutoConfiguration指定的值，将这些值作为自动配置类导入到容器中  
自动配置类就生效，帮我们进行自动配置工作

J2EE的整体整合解决方案和自动配置都在

### spring-boot-autoconfigure-1.5.9.RELEASE.jar ###

![这里写图片描述][70 2]

[70]: /images/20220515/fc68dbcef1df447b9c8980e7fa8f3240.png
[70 1]: /images/20220515/8d921d04e5a14e0888dedc38b4a76a72.png
[70 2]: /images/20220515/0d8237f9e9e74000b6520d038a77863a.png