然后引入要自动注入的组件依赖然后现application.properties中加上相应配置就可以自动注入这个组件那么下面看看自动注入组件是如何实现的

类如下

Retention(RetentionPolicy.RUNTIME)

Documented

{AutoConfigurationExcludeFilter.class}

public

Retention(RetentionPolicy.RUNTIME)

Documented

Import({AutoConfigurationImportSelector.class})

public

spring.boot.enableautoconfiguration;Class?[]

exclude()

}这个类又通过Import({AutoConfigurationImportSelector.class})

3、AutoConfigurationImportSelector这个bean查看这个bean

public

AutoConfigurationImportSelectorimplements

ResourceLoaderAware,BeanFactoryAware,

EnvironmentAware,

{}4、这个AutoConfigurationImportSelector类继承了DeferredImportSelector最终继承了ImportSelector重写这个类的selectImports方法可以快速导入一个bean查看selectImports方法

Overridepublic

selectImports(AnnotationMetadata

annotationMetadata)

(!isEnabled(annotationMetadata))

{return

NO_IMPORTS;}AutoConfigurationMetadata

AutoConfigurationMetadataLoader.loadMetadata(this.beanClassLoader);AnnotationAttributes

attributes

getAttributes(annotationMetadata);ListString

configurations

getCandidateConfigurations(annotationMetadata,attributes);configurations

removeDuplicates(configurations);SetString

exclusions

getExclusions(annotationMetadata,

attributes);checkExcludedClasses(configurations,

exclusions);configurations.removeAll(exclusions);configurations

autoConfigurationMetadata);fireAutoConfigurationImportEvents(configurations,

exclusions);return

StringUtils.toStringArray(configurations);}5、查看ListString

configurations

getCandidateConfigurations(annotationMetadata,

attributes);

getCandidateConfigurations(AnnotationMetadata

attributes)

SpringFactoriesLoader.loadFactoryNames(getSpringFactoriesLoaderFactoryClass(),

getBeanClassLoader());Assert.notEmpty(configurations,No

auto

configurations;}6、这个方法最终会调用loadSpringFactories方法这个方法把META-INF/spring.factories定义的类全部读到出来

Auto

org.springframework.boot.autoconfigure.EnableAutoConfiguration\

org.springframework.boot.autoconfigure.admin.SpringApplicationAdminJmxAutoConfiguration,\

org.springframework.boot.autoconfigure.aop.AopAutoConfiguration,\

org.springframework.boot.autoconfigure.amqp.RabbitAutoConfiguration,\

org.springframework.boot.autoconfigure.batch.BatchAutoConfiguration,\private

static

(MultiValueMap)cache.get(classLoader);if

(result

classLoader.getResources(META-INF/spring.factories)

ClassLoader.getSystemResources(META-INF/spring.factories);LinkedMultiValueMap

result

LinkedMultiValueMap();while(urls.hasMoreElements())

{URL

(URL)urls.nextElement();UrlResource

resource

PropertiesLoaderUtils.loadProperties(resource);Iterator

var6

properties.entrySet().iterator();while(var6.hasNext())

{Entry?,

Arrays.asList(StringUtils.commaDelimitedListToStringArray((String)entry.getValue()));result.addAll((String)entry.getKey(),

factoryClassNames);}}cache.put(classLoader,

result);return

IllegalArgumentException(Unable

load

var9);}}}7、最终spring会根据这些组件中定义的注入条件将这些组件自动注入org.springframework.boot.autoconfigure下放了所有自动注入的组件以aop这个组件为例

Configuration

Advice.class,这些class存在时才注入也就是说当引入相关依赖包时注入AnnotatedElement.class

ConditionalOnClass({

Advice.class,AnnotatedElement.class

//当配置文件中有spring.aop

{ConfigurationEnableAspectJAutoProxy(proxyTargetClass

false)ConditionalOnProperty(prefix

spring.aop,

JdkDynamicAutoProxyConfiguration

{}ConfigurationEnableAspectJAutoProxy(proxyTargetClass

true)ConditionalOnProperty(prefix

spring.aop,

--dependencygroupIdorg.apache.tomcat.embed/groupIdartifactIdtomcat-embed-core/artifactIdversion8.5.16/version/dependency!--

tomcat对jsp支持

--dependencygroupIdorg.apache.tomcat/groupIdartifactIdtomcat-jasper/artifactIdversion8.5.16/version/dependency/dependencies2、新建一个servlet文件

public

指定端口号tomcatServer.setPort(PORT);//

是否设置自动部署tomcatServer.getHost().setAutoDeploy(false);//

创建上下文StandardContext

StandardContext();standardContex.setPath(CONTEX_PATH);//

监听上下文standardContex.addLifecycleListener(new

Tomcat.FixContextListener());//

tomcat容器添加standardContextomcatServer.getHost().addChild(standardContex);//

创建ServlettomcatServer.addServlet(CONTEX_PATH,

SERVLET_NAME,

servleturl映射standardContex.addServletMappingDecoded(/index,

SERVLET_NAME);tomcatServer.start();System.out.println(tomcat服务器启动成功..);//

异步进行接收请求tomcatServer.getServer().await();}

}4、运行main在浏览器输入

http://localhost:8080/clock/index

spring

boot在启动的时候启动一个tomcat实际上它启动的方式也是上面那么启动方式

2、tomcat加载流程

tomcat也是一个组件那么它的引入方式也是通过spring.factories文件注入的

3、查看ServletWebServerFactoryAutoConfiguration这个类

ServletWebServerFactoryAutoConfiguration这个类用import快速导入了EmbeddedTomcat类

4、查看EmbeddedTomcat类

这个类注入了TomcatServletWebServerFactory这个bean

ConfigurationConditionalOnClass({

Servlet.class,

})ConditionalOnMissingBean(value

search

tomcatServletWebServerFactory()

{return

TomcatServletWebServerFactory();}}4、查看TomcatServletWebServerFactory类

这个方法启动了一个tomcat那么这个方法是在哪个地方调用的可以在这个方法上打上断点查看它的调用链

public

getWebServer(ServletContextInitializer...

initializers)

this.createTempDir(tomcat);tomcat.setBaseDir(baseDir.getAbsolutePath());Connector

connector

Connector(this.protocol);tomcat.getService().addConnector(connector);this.customizeConnector(connector);tomcat.setConnector(connector);tomcat.getHost().setAutoDeploy(false);this.configureEngine(tomcat.getEngine());Iterator

var5

this.additionalTomcatConnectors.iterator();while(var5.hasNext())

{Connector

(Connector)var5.next();tomcat.getService().addConnector(additionalConnector);}this.prepareContext(tomcat.getHost(),

initializers);return

this.getTomcatWebServer(tomcat);}5、在getWebServer方法打断点然后启动spring

6、启动流程分析

了一个SpringApplication对象然后执行了run方法

public

SpringApplication(primarySources)).run(args);}SpringApplication结构方法

public

SpringApplication(ResourceLoader

resourceLoader,

resourceLoader;Assert.notNull(primarySources,

PrimarySources

null);//保存主类this.primarySources

new

LinkedHashSet(Arrays.asList(primarySources));//判断当前是什么类型项目this.webApplicationType

WebApplicationType.deduceFromClasspath();//从类路径下找到META-INF/spring.factories配置的所有ApplicationContextInitializersetInitializers((Collection)

getSpringFactoriesInstances(ApplicationContextInitializer.class));//从类路径下找到META-INF/spring.factories配置的所有ApplicationListenersetListeners((Collection)

getSpringFactoriesInstances(ApplicationListener.class));this.mainApplicationClass

}run方法

StopWatch();stopWatch.start();ConfigurableApplicationContext

context

null;CollectionSpringBootExceptionReporter

exceptionReporters

ArrayList();configureHeadlessProperty();//从类路径下META‐INF/spring.factories取得SpringApplicationRunListenersSpringApplicationRunListeners

listeners

//回调所有的获取SpringApplicationRunListener.starting()方法listeners.starting();try

applicationArguments

DefaultApplicationArguments(args);//准备环境ConfigurableEnvironment

environment

prepareEnvironment(listeners,applicationArguments);configureIgnoreBeanInfo(environment);//创回调SpringApplicationRunListener.environmentPrepared()

//表示环境准备完成//打印Banner

printBanner(environment);//根据环境创建contextcontext

createApplicationContext();//错误的异常报表exceptionReporters

getSpringFactoriesInstances(SpringBootExceptionReporter.class,new

Class[]

ConfigurableApplicationContext.class

context);//准备上下文环境;//将environment保存到ioc中//applyInitializers()调用所有的ApplicationContextInitializer的initialize方法

//调用所有的SpringApplicationRunListener的contextPrepared()prepareContext(context,

environment,

applicationArguments,printedBanner);

//SpringApplicationRunListener的contextLoaded

//刷新容器

//扫描创建加载所有组件refreshContext(context);afterRefresh(context,

applicationArguments);stopWatch.stop();if

{new

StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(),

stopWatch);}//所有的SpringApplicationRunListener回调started方法listeners.started(context);//获取所有的ApplicationRunner和CommandLineRunner进行调用callRunners(context,

(Throwable

{//所有的SpringApplicationRunListener的running()listeners.running(context);}catch

(Throwable

IllegalStateException(ex);}return

context;

boot内嵌的web容器是tomcat那么如果我们不想用tomcat

1、修改pom

dependenciesdependencygroupIdorg.springframework.boot/groupIdartifactIdspring-boot-starter-web/artifactIdexclusionsexclusiongroupIdorg.springframework.boot/groupIdartifactIdspring-boot-starter-tomcat/artifactId/exclusion/exclusions/dependencydependencygroupIdorg.springframework.boot/groupIdartifactIdspring-boot-starter-undertow/artifactId/dependency/dependencies这个再启动spring