SpringBoot快速入门-查看SpringBoot的启动器中封装的组件

发表于2022年9月23日2023年7月15日作者 IT之美

上一节我们已经对SpringBoot启动器的作用做了讲解，其主要作用就是将一个相关功能的开发场景的搭建进行整合，整合了这个功能的各种依赖，并实现了大量的默认配置，从而减少了用户处理依赖和配置的工作。
我们这一节就来看看一个SpringBoot的启动器的启动器内部帮我们组织了多少的相关依赖，我们就以Web-starter为例来看看SpringBoot内部为我们封装了多少组件。

1、我们在pom文件中添加了依赖：

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-web</artifactId>
</dependency>

2、项目启动类的main方法中编写代码：

public static void main( String[] args ) {
	ConfigurableApplicationContext run = SpringApplication.run(App.class, args);
	System.out.println("Spring Cloud 默认加载的组件数:" + run.getBeanDefinitionCount());
	Arrays.stream(run.getBeanDefinitionNames()).forEach(System.out::println);
}

3、输出：

SpringBoot Web-starter默认加载的组件数:151

org.springframework.context.annotation.internalConfigurationAnnotationProcessor
org.springframework.context.annotation.internalAutowiredAnnotationProcessor
org.springframework.context.annotation.internalCommonAnnotationProcessor
org.springframework.context.event.internalEventListenerProcessor
org.springframework.context.event.internalEventListenerFactory
app
org.springframework.boot.autoconfigure.internalCachingMetadataReaderFactory
springBootConfiguration_1
springBootConfiguration_2
org.springframework.boot.autoconfigure.AutoConfigurationPackages
org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration
propertySourcesPlaceholderConfigurer
org.springframework.boot.autoconfigure.websocket.servlet.WebSocketServletAutoConfiguration$TomcatWebSocketConfiguration
websocketServletWebServerCustomizer
org.springframework.boot.autoconfigure.websocket.servlet.WebSocketServletAutoConfiguration
org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryConfiguration$EmbeddedTomcat
tomcatServletWebServerFactory
org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryAutoConfiguration
servletWebServerFactoryCustomizer
tomcatServletWebServerFactoryCustomizer
org.springframework.boot.context.properties.ConfigurationPropertiesBindingPostProcessor
org.springframework.boot.context.internalConfigurationPropertiesBinderFactory
org.springframework.boot.context.internalConfigurationPropertiesBinder
org.springframework.boot.context.properties.BoundConfigurationProperties
org.springframework.boot.context.properties.EnableConfigurationPropertiesRegistrar.methodValidationExcludeFilter
server-org.springframework.boot.autoconfigure.web.ServerProperties
webServerFactoryCustomizerBeanPostProcessor
errorPageRegistrarBeanPostProcessor
org.springframework.boot.autoconfigure.web.servlet.DispatcherServletAutoConfiguration$DispatcherServletConfiguration
dispatcherServlet
spring.mvc-org.springframework.boot.autoconfigure.web.servlet.WebMvcProperties
org.springframework.boot.autoconfigure.web.servlet.DispatcherServletAutoConfiguration$DispatcherServletRegistrationConfiguration
dispatcherServletRegistration
org.springframework.boot.autoconfigure.web.servlet.DispatcherServletAutoConfiguration
org.springframework.boot.autoconfigure.task.TaskExecutionAutoConfiguration
taskExecutorBuilder
applicationTaskExecutor
spring.task.execution-org.springframework.boot.autoconfigure.task.TaskExecutionProperties
org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration$WhitelabelErrorViewConfiguration
error
beanNameViewResolver
org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration$DefaultErrorViewResolverConfiguration
conventionErrorViewResolver
spring.resources-org.springframework.boot.autoconfigure.web.ResourceProperties
spring.web-org.springframework.boot.autoconfigure.web.WebProperties
org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration
errorAttributes
basicErrorController
errorPageCustomizer
preserveErrorControllerTargetClassPostProcessor
org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration$EnableWebMvcConfiguration
requestMappingHandlerAdapter
requestMappingHandlerMapping
welcomePageHandlerMapping
localeResolver
themeResolver
flashMapManager
mvcConversionService
mvcValidator
mvcContentNegotiationManager
mvcPatternParser
mvcUrlPathHelper
mvcPathMatcher
viewControllerHandlerMapping
beanNameHandlerMapping
routerFunctionMapping
resourceHandlerMapping
mvcResourceUrlProvider
defaultServletHandlerMapping
handlerFunctionAdapter
mvcUriComponentsContributor
httpRequestHandlerAdapter
simpleControllerHandlerAdapter
handlerExceptionResolver
mvcViewResolver
mvcHandlerMappingIntrospector
viewNameTranslator
org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration$WebMvcAutoConfigurationAdapter
defaultViewResolver
viewResolver
requestContextFilter
org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration
formContentFilter
org.springframework.boot.autoconfigure.jmx.JmxAutoConfiguration
mbeanExporter
objectNamingStrategy
mbeanServer
org.springframework.boot.autoconfigure.admin.SpringApplicationAdminJmxAutoConfiguration
springApplicationAdminRegistrar
org.springframework.boot.autoconfigure.aop.AopAutoConfiguration$ClassProxyingConfiguration
forceAutoProxyCreatorToUseClassProxying
org.springframework.boot.autoconfigure.aop.AopAutoConfiguration
org.springframework.boot.autoconfigure.availability.ApplicationAvailabilityAutoConfiguration
applicationAvailability
org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration$Jackson2ObjectMapperBuilderCustomizerConfiguration
standardJacksonObjectMapperBuilderCustomizer
spring.jackson-org.springframework.boot.autoconfigure.jackson.JacksonProperties
org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration$JacksonObjectMapperBuilderConfiguration
jacksonObjectMapperBuilder
org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration$ParameterNamesModuleConfiguration
parameterNamesModule
org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration$JacksonObjectMapperConfiguration
jacksonObjectMapper
org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration
jsonComponentModule
org.springframework.boot.autoconfigure.context.ConfigurationPropertiesAutoConfiguration
org.springframework.boot.autoconfigure.context.LifecycleAutoConfiguration
lifecycleProcessor
spring.lifecycle-org.springframework.boot.autoconfigure.context.LifecycleProperties
org.springframework.boot.autoconfigure.http.HttpMessageConvertersAutoConfiguration$StringHttpMessageConverterConfiguration
stringHttpMessageConverter
org.springframework.boot.autoconfigure.http.JacksonHttpMessageConvertersConfiguration$MappingJackson2HttpMessageConverterConfiguration
mappingJackson2HttpMessageConverter
org.springframework.boot.autoconfigure.http.JacksonHttpMessageConvertersConfiguration
org.springframework.boot.autoconfigure.http.HttpMessageConvertersAutoConfiguration
messageConverters
org.springframework.boot.autoconfigure.info.ProjectInfoAutoConfiguration
spring.info-org.springframework.boot.autoconfigure.info.ProjectInfoProperties
org.springframework.boot.autoconfigure.sql.init.SqlInitializationAutoConfiguration
spring.sql.init-org.springframework.boot.autoconfigure.sql.init.SqlInitializationProperties
org.springframework.boot.sql.init.dependency.DatabaseInitializationDependencyConfigurer$DependsOnDatabaseInitializationPostProcessor
org.springframework.boot.autoconfigure.task.TaskSchedulingAutoConfiguration
scheduledBeanLazyInitializationExcludeFilter
taskSchedulerBuilder
spring.task.scheduling-org.springframework.boot.autoconfigure.task.TaskSchedulingProperties
org.springframework.boot.autoconfigure.web.client.RestTemplateAutoConfiguration
restTemplateBuilderConfigurer
restTemplateBuilder
org.springframework.boot.autoconfigure.web.embedded.EmbeddedWebServerFactoryCustomizerAutoConfiguration$TomcatWebServerFactoryCustomizerConfiguration
tomcatWebServerFactoryCustomizer
org.springframework.boot.autoconfigure.web.embedded.EmbeddedWebServerFactoryCustomizerAutoConfiguration
org.springframework.boot.autoconfigure.web.servlet.HttpEncodingAutoConfiguration
characterEncodingFilter
localeCharsetMappingsCustomizer
org.springframework.boot.autoconfigure.web.servlet.MultipartAutoConfiguration
multipartConfigElement
multipartResolver
spring.servlet.multipart-org.springframework.boot.autoconfigure.web.servlet.MultipartProperties
org.springframework.boot.devtools.autoconfigure.LocalDevToolsAutoConfiguration$RestartConfiguration
restartingClassPathChangedEventListener
classPathFileSystemWatcher
classPathRestartStrategy
fileSystemWatcherFactory
conditionEvaluationDeltaLoggingListener
org.springframework.boot.devtools.autoconfigure.LocalDevToolsAutoConfiguration$LiveReloadConfiguration
liveReloadServer
optionalLiveReloadServer
liveReloadServerEventListener
org.springframework.boot.devtools.autoconfigure.LocalDevToolsAutoConfiguration
spring.devtools-org.springframework.boot.devtools.autoconfigure.DevToolsProperties
org.springframework.aop.config.internalAutoProxyCreator

从输出结果，我们可以看到，SpringBoot Web-starter默认加载的组件数:151。
以前如果使用过Servlet+Tomcat开发的同学都应该了解，使用Servlet+Tomcat开发的项目，都需要在Servlet中对request入参和response返回的结果进行字符编码处理，否则中文就会乱码。
SpringBoot项目现在不需要我们手动处理了，那原因就是SpringBoot已经做了默认处理，我们从上面输出的组件可以看到，SpringBoot Web-starter加载的组件中，默认就加载了这个组件：characterEncodingFilter，这个就是负责字符编码转换。
再比如使用SpringMVC开发的Web项目，主要负责响应前端请求，并进行请求分发的类是DispatcherServlet，从上面的输出结果上，也可以看到这个组件。

所以，可以简单理解为：SpringBoot+SpringBoot-starter就是各类开发场景的一个demo项目，可以方便我们快速搭建项目，开发项目。