1.spring-boot启动的main入口
SpringBootApplication注解，点击注解，发现这个注解中的@EnableAutoConfiguration 这个注解表示开启自动配置，自动配置一些组件
@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 {};
}
这个注解中import这个注解里
AutoConfigurationImportSelector这个类就会扫描所有包，找到所有的配置类，点开这个类
里面最重要的就是这个selectImports方法，我们来分析一下：
public String[] selectImports(AnnotationMetadata annotationMetadata) {
if (!this.isEnabled(annotationMetadata)) {
return NO_IMPORTS;
} else {
AutoConfigurationMetadata autoConfigurationMetadata = AutoConfigurationMetadataLoader.loadMetadata(this.beanClassLoader);
AnnotationAttributes attributes = this.getAttributes(annotationMetadata);
List<String> configurations = this.getCandidateConfigurations(annotationMetadata, attributes);
configurations = this.removeDuplicates(configurations);
Set<String> exclusions = this.getExclusions(annotationMetadata, attributes);
this.checkExcludedClasses(configurations, exclusions);
configurations.removeAll(exclusions);
configurations = this.filter(configurations, autoConfigurationMetadata);
this.fireAutoConfigurationImportEvents(configurations, exclusions);
return StringUtils.toStringArray(configurations);
}
}
AutoConfigurationMetadata autoConfigurationMetadata = AutoConfigurationMetadataLoader.loadMetadata(this.beanClassLoader);//会去调用loadMetadata方法，传入的是一个beanClassLoader
查看loadMetadata发现其调用的是重载方法
public static AutoConfigurationMetadata loadMetadata(ClassLoader classLoader) { return loadMetadata(classLoader, "META-INF/spring-autoconfigure-metadata.properties"); } static AutoConfigurationMetadata loadMetadata(ClassLoader classLoader, String path) { try { Enumeration<URL> urls = classLoader != null ? classLoader.getResources(path) : ClassLoader.getSystemResources(path); Properties properties = new Properties(); while(urls.hasMoreElements()) { properties.putAll(PropertiesLoaderUtils.loadProperties(new UrlResource((URL)urls.nextElement()))); } return loadMetadata(properties); } catch (IOException var4) { throw new IllegalArgumentException("Unable to load @ConditionalOnClass location [" + path + "]", var4); } }
打断点后发现是把“”META-INF/spring-autoconfigure-metadata.properties“”这个文件变成一个properties返回
然后在org.springframework.boot下随便找一个配置类看一下具体实现，我这里找的是
HttpEncodingAutoConfiguration
这个类上面有个
@EnableConfigurationProperties({HttpEncodingProperties.class})
而点开这个类，里面就见到我熟悉的
ConfigurationProperties
说明我们要找的自动配置的类就在这里，
@ConfigurationProperties(
prefix = "spring.http.encoding"
)
这个类里面也是我们能够在springboot中能够使用的所有字段，验证一下
原文：https://www.cnblogs.com/qunincey/p/9729775.html