第SpringBoot超詳細分析啟動流程目錄1、創(chuàng)建SpringApplication1.1、判斷web類型1.2、加載上下文初始化器1.3、加載監(jiān)聽器1.4、獲得引導類類型2、執(zhí)行SpringApplication的run方法啟動Springboot2.1、準備environment2.1.1、創(chuàng)建environment2.1.2、配置environment2.2、打印Banner2.3、創(chuàng)建Spring上下文2.4、準備上下文2.4.1、ApplicationContext的后置處理2.4.2、應用初始化器2.4.3、獲取sources2.4.4、加載2.5、刷新上下文2.6、上下文刷新后2.7、執(zhí)行回調(diào)Springboot啟動類

@SpringBootApplication

publicclassTestApplication{

publicstaticvoidmain(String[]args){

SpringApplication.run(TestApplication.class,args);

SpringBootApplication注解

@Target(ElementType.TYPE)

@Retention(RetentionPolicy.RUNTIME)

@Documented

@Inherited

@SpringBootConfiguration

@EnableAutoConfiguration

@ComponentScan(excludeFilters={@Filter(type=FilterType.CUSTOM,classes=TypeExcludeFilter.class),

@Filter(type=FilterType.CUSTOM,classes=AutoConfigurationExcludeFilter.class)})

public@interfaceSpringBootApplication{

@SpringBootApplication注解上標注了@EnableAutoConfiguration，表示TestApplication是引導類。

Springboot的啟動方法中傳入了兩個參數(shù)，引導類，和程序參數(shù)。

publicstaticConfigurableApplicationContextrun(ClassprimarySource,String...args){

returnrun(newClass[]{primarySource},args);

調(diào)用run方法

publicstaticConfigurableApplicationContextrun(Class[]primarySources,String[]args){

returnnewSpringApplication(primarySources).run(args);

run方法中有兩步，創(chuàng)建SpringApplication和執(zhí)行SpringApplication的run方法。

1、創(chuàng)建SpringApplication

SpringApplication的構造器

publicSpringApplication(Class...primarySources){

this(null,primarySources);

privateResourceLoaderresourceLoader;

privateSetClassprimarySources;

publicSpringApplication(ResourceLoaderresourceLoader,Class...primarySources){

//將resourceLoader賦值成員變量，此處是null

this.resourceLoader=resourceLoader;

Assert.notNull(primarySources,"PrimarySourcesmustnotbenull");

//將引導類賦值成員變量

this.primarySources=newLinkedHashSet(Arrays.asList(primarySources));

//判斷web類型，賦值成員變量

this.webApplicationType=WebApplicationType.deduceFromClasspath();

//加載初始化器

setInitializers((Collection)getSpringFactoriesInstances(ApplicationContextInitializer.class));

//加載監(jiān)聽器

setListeners((Collection)getSpringFactoriesInstances(ApplicationListener.class));

//獲得引導類

this.mainApplicationClass=deduceMainApplicationClass();

1.1、判斷web類型

//org.springframework.boot.WebApplicationType#deduceFromClasspath

staticWebApplicationTypededuceFromClasspath(){

//WEBFLUX_INDICATOR_CLASS="org.springframework.web.reactive.DispatcherHandler";

//JERSEY_INDICATOR_CLASS="org.glassfish.jersey.servlet.ServletContainer";

if(ClassUtils.isPresent(WEBFLUX_INDICATOR_CLASS,null)!ClassUtils.isPresent(WEBMVC_INDICATOR_CLASS,null)

!ClassUtils.isPresent(JERSEY_INDICATOR_CLASS,null)){

returnWebApplicationType.REACTIVE;

//SERVLET_INDICATOR_CLASSES={"javax.servlet.Servlet",

"org.springframework.web.context.ConfigurableWebApplicationContext"}

for(StringclassName:SERVLET_INDICATOR_CLASSES){

if(!ClassUtils.isPresent(className,null)){

returnWebApplicationType.NONE;

returnWebApplicationType.SERVLET;

1.2、加載上下文初始化器

利用spi加載ApplicationContextInitializer的實現(xiàn)類

privateTCollectionTgetSpringFactoriesInstances(ClassTtype){

returngetSpringFactoriesInstances(type,newClass[]{});

privateTCollectionTgetSpringFactoriesInstances(ClassTtype,Class[]parameterTypes,Object...args){

//獲取classloader

ClassLoaderclassLoader=getClassLoader();

//Usenamesandensureuniquetoprotectagainstduplicates

//獲取配置文件中接口實現(xiàn)類的全限定名

SetStringnames=newLinkedHashSet(SpringFactoriesLoader.loadFactoryNames(type,classLoader));

//初始化

ListTinstances=createSpringFactoriesInstances(type,parameterTypes,classLoader,args,names);

AnnotationAwareOrderComparator.sort(instances);

//返回

returninstances;

publicClassLoadergetClassLoader(){

if(this.resourceLoader!=null){

returnthis.resourceLoader.getClassLoader();

returnClassUtils.getDefaultClassLoader();

privateTListTcreateSpringFactoriesInstances(ClassTtype,Class[]parameterTypes,

ClassLoaderclassLoader,Object[]args,SetStringnames){

ListTinstances=newArrayList(names.size());

for(Stringname:names){

try{

ClassinstanceClass=ClassUtils.forName(name,classLoader);

Assert.isAssignable(type,instanceClass);

Constructorconstructor=instanceClass.getDeclaredConstructor(parameterTypes);

Tinstance=(T)BeanUtils.instantiateClass(constructor,args);

instances.add(instance);

catch(Throwableex){

thrownewIllegalArgumentException("Cannotinstantiate"+type+":"+name,ex);

returninstances;

將初始化好的上下文初始化器設置到成員變量

//privateListApplicationContextInitializerinitializers;

publicvoidsetInitializers(CollectionextendsApplicationContextInitializerinitializers){

this.initializers=newArrayList(initializers);

1.3、加載監(jiān)聽器

將初始化好的監(jiān)聽器設置到成員變量

//privateListApplicationListenerlisteners;

publicvoidsetListeners(CollectionextendsApplicationListenerlisteners){

this.listeners=newArrayList(listeners);

1.4、獲得引導類類型

privateClassdeduceMainApplicationClass(){

try{

StackTraceElement[]stackTrace=newRuntimeException().getStackTrace();

for(StackTraceElementstackTraceElement:stackTrace){

//獲取main方法的類

if("main".equals(stackTraceElement.getMethodName())){

returnClass.forName(stackTraceElement.getClassName());

catch(ClassNotFoundExceptionex){

//Swallowandcontinue

returnnull;

}

2、執(zhí)行SpringApplication的run方法啟動Springboot

publicConfigurableApplicationContextrun(String...args){

//啟動停止監(jiān)聽器

StopWatchstopWatch=newStopWatch();

stopWatch.start();

//Spring上下文

ConfigurableApplicationContextcontext=null;

//錯誤導出

CollectionSpringBootExceptionReporterexceptionReporters=newArrayList();

configureHeadlessProperty();

//運行時監(jiān)聽器

SpringApplicationRunListenerslisteners=getRunListeners(args);

//啟動運行時監(jiān)聽器

listeners.starting();

try{

//生成ApplicationArguments

ApplicationArgumentsapplicationArguments=newDefaultApplicationArguments(args);

//準備environment

ConfigurableEnvironmentenvironment=prepareEnvironment(listeners,applicationArguments);

configureIgnoreBeanInfo(environment);

//打印banner

BannerprintedBanner=printBanner(environment);

//創(chuàng)建Spring上下文

context=createApplicationContext();

exceptionReporters=getSpringFactoriesInstances(SpringBootExceptionReporter.class,

newClass[]{ConfigurableApplicationContext.class},context);

//準備上下文

prepareContext(context,environment,listeners,applicationArguments,printedBanner);

//刷新上下文

refreshContext(context);

//上下文刷新后

afterRefresh(context,applicationArguments);

//停止停止監(jiān)聽器

stopWatch.stop();

if(this.logStartupInfo){

newStartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(),stopWatch);

//停止運行時監(jiān)聽器

listeners.started(context);

//執(zhí)行回調(diào)

callRunners(context,applicationArguments);

catch(Throwableex){

handleRunFailure(context,ex,exceptionReporters,listeners);

thrownewIllegalStateException(ex);

try{

listeners.running(context);

catch(Throwableex){

handleRunFailure(context,ex,exceptionReporters,null);

thrownewIllegalStateException(ex);

returncontext;

}

2.1、準備environment

privateConfigurableEnvironmentprepareEnvironment(SpringApplicationRunListenerslisteners,

ApplicationArgumentsapplicationArguments){

//Createandconfiguretheenvironment

//創(chuàng)建environment

ConfigurableEnvironmentenvironment=getOrCreateEnvironment();

//配置environment

configureEnvironment(environment,applicationArguments.getSourceArgs());

ConfigurationPropertySources.attach(environment);

listeners.environmentPrepared(environment);

bindToSpringApplication(environment);

if(!this.isCustomEnvironment){

environment=newEnvironmentConverter(getClassLoader()).convertEnvironmentIfNecessary(environment,

deduceEnvironmentClass());

ConfigurationPropertySources.attach(environment);

returnenvironment;

}

2.1.1、創(chuàng)建environment

privateConfigurableEnvironmentgetOrCreateEnvironment(){

if(this.environment!=null){

returnthis.environment;

switch(this.webApplicationType){

caseSERVLET:

returnnewStandardServletEnvironment();

caseREACTIVE:

returnnewStandardReactiveWebEnvironment();

default:

returnnewStandardEnvironment();

}

這里根據(jù)web類型創(chuàng)建不同的environment

2.1.2、配置environment

protectedvoidconfigureEnvironment(ConfigurableEnvironmentenvironment,String[]args){

if(this.addConversionService){

//轉(zhuǎn)換服務

ConversionServiceconversionService=ApplicationConversionService.getSharedInstance();

environment.setConversionService((ConfigurableConversionService)conversionService);

configurePropertySources(environment,args);

configureProfiles(environment,args);

配置PropertySources

protectedvoidconfigurePropertySources(ConfigurableEnvironmentenvironment,String[]args){

MutablePropertySourcessources=environment.getPropertySources();

if(this.defaultProperties!=null!this.defaultProperties.isEmpty()){

sources.addLast(newMapPropertySource("defaultProperties",this.defaultProperties));

if(this.addCommandLinePropertiesargs.length0){

Stringname=CommandLinePropertySource.COMMAND_LINE_PROPERTY_SOURCE_NAME;

if(sources.contains(name)){

PropertySourcesource=sources.get(name);

CompositePropertySourcecomposite=newCompositePropertySource(name);

composite.addPropertySource(

newSimpleCommandLinePropertySource("springApplicationCommandLineArgs",args));

composite.addPropertySource(source);

sources.replace(name,composite);

else{

sources.addFirst(newSimpleCommandLinePropertySource(args));

主要為了在PropertySources添加一個SimpleCommandLinePropertySource。

配置profiles

protectedvoidconfigureProfiles(ConfigurableEnvironmentenvironment,String[]args){

SetStringprofiles=newLinkedHashSet(this.additionalProfiles);

profiles.addAll(Arrays.asList(environment.getActiveProfiles()));

environment.setActiveProfiles(StringUtils.toStringArray(profiles));

將profile添加到environment

2.2、打印Banner

privateBanner.ModebannerMode=Banner.Mode.CONSOLE;

privateBannerprintBanner(ConfigurableEnvironmentenvironment){

//無需打印

if(this.bannerMode==Banner.Mode.OFF){

returnnull;

ResourceLoaderresourceLoader=(this.resourceLoader!=null)this.resourceLoader

:newDefaultResourceLoader(getClassLoader());

SpringApplicationBannerPrinterbannerPrinter=newSpringApplicationBannerPrinter(resourceLoader,this.banner);

if(this.bannerMode==Mode.LOG){

returnbannerPrinter.print(environment,this.mainApplicationClass,logger);

returnbannerPrinter.print(environment,this.mainApplicationClass,System.out);

2.3、創(chuàng)建Spring上下文

//DEFAULT_SERVLET_WEB_CONTEXT_CLASS="org.springframework.boot."http://+"web.servlet.context.AnnotationConfigServletWebServerApplicationContext";

//DEFAULT_REACTIVE_WEB_CONTEXT_CLASS="org.springframework."http://+"boot.web.reactive.context.AnnotationConfigReactiveWebServerApplicationContext";

//DEFAULT_CONTEXT_CLASS="org.springframework.context."

//+"annotation.AnnotationConfigApplicationContext";

protectedConfigurableApplicationContextcreateApplicationContext(){

ClasscontextClass=this.applicationContextClass;

if(contextClass==null){

try{

switch(this.webApplicationType){

caseSERVLET:

contextClass=Class.forName(DEFAULT_SERVLET_WEB_CONTEXT_CLASS);

break;

caseREACTIVE:

contextClass=Class.forName(DEFAULT_REACTIVE_WEB_CONTEXT_CLASS);

break;

default:

contextClass=Class.forName(DEFAULT_CONTEXT_CLASS);

catch(ClassNotFoundExceptionex){

thrownewIllegalStateException(

"UnablecreateadefaultApplicationContext,pleasespecifyanApplicationContextClass",ex);

//初始化上下文并返回

return(ConfigurableApplicationContext)BeanUtils.instantiateClass(contextClass);

}

2.4、準備上下文

privatevoidprepareContext(ConfigurableApplicationContextcontext,ConfigurableEnvironmentenvironment,

SpringApplicationRunListenerslisteners,ApplicationArgumentsapplicationArguments,BannerprintedBanner){

context.setEnvironment(environment);

//ApplicationContext的后置處理

postProcessApplicationContext(context);

//應用初始化器

applyInitializers(context);

//運行時監(jiān)聽器的準備上下文監(jiān)聽

listeners.contextPrepared(context);

if(this.logStartupInfo){

logStartupInfo(context.getParent()==null);

logStartupProfileInfo(context);

//Addbootspecificsingletonbeans

//獲取beanFactory

ConfigurableListableBeanFactorybeanFactory=context.getBeanFactory();

//將程序入?yún)⒆詁eanspringApplicationArguments

beanFactory.registerSingleton("springApplicationArguments",applicationArguments);

//將banner注冊beanspringBootBanner

if(printedBanner!=null){

beanFactory.registerSingleton("springBootBanner",printedBanner);

//設置BeanDefinition是否允許重寫

if(beanFactoryinstanceofDefaultListableBeanFactory){

((DefaultListableBeanFactory)beanFactory)

.setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);

//初始化允許懶加載，設置BeanfactorypostProcessor

if(this.lazyInitialization){

context.addBeanFactoryPostProcessor(newLazyInitializationBeanFactoryPostProcessor());

//Loadthesources

//獲取source

SetObjectsources=getAllSources();

Assert.notEmpty(sources,"Sourcesmustnotbeempty");

load(context,sources.toArray(newObject[0]));

//運行時監(jiān)聽器，上下文加載完成

listeners.contextLoaded(context);

2.4.1、ApplicationContext的后置處理

protectedvoidpostProcessApplicationContext(ConfigurableApplicationContextcontext){

//注冊beanNameGenerator

if(this.beanNameGenerator!=null){

context.getBeanFactory().registerSingleton(AnnotationConfigUtils.CONFIGURATION_BEAN_NAME_GENERATOR,

this.beanNameGenerator);

//注冊resourceLoader

if(this.resourceLoader!=null){

if(contextinstanceofGenericApplicationContext){

((GenericApplicationContext)context).setResourceLoader(this.resourceLoader);

if(contextinstanceofDefaultResourceLoader){

((DefaultResourceLoader)context).setClassLoader(this.resourceLoader.getClassLoader());

//設置ConversionService

if(this.addConversionService){

context.getBeanFactory().setConversionService(ApplicationConversionService.getSharedInstance());

//org.springframework.boot.convert.ApplicationConversionService#getSharedInstance

publicstaticConversionServicegetSharedInstance(){

ApplicationConversionServicesharedInstance=ApplicationConversionService.sharedInstance;

if(sharedInstance==null){

synchronized(ApplicationConversionService.class){

sharedInstance=ApplicationConversionService.sharedInstance;

if(sharedInstance==null){

sharedInstance=newApplicationConversionService();

ApplicationConversionService.sharedInstance=sharedInstance;

returnsharedInstance;

2.4.2、應用初始化器

protectedvoidapplyInitializers(ConfigurableApplicationContextcontext){

for(ApplicationContextInitializerinitializer:getInitializers()){

ClassrequiredType=GenericTypeResolver.resolveTypeArgument(initializer.getClass(),

ApplicationContextInitializer.class);

Assert.isInstanceOf(requiredType,context,"Unabletocallinitializer.");

initializer.initialize(context);

執(zhí)行所有實現(xiàn)了ApplicationContextInitializer接口的類的initialize方法。

2.4.3、獲取sources

publicSetObjectgetAllSources(){

SetObjectallSources=newLinkedHashSet();

if(!CollectionUtils.isEmpty(this.primarySources)){

allSources.addAll(this.primarySources);

if(!CollectionUtils.isEmpty(this.sources)){

allSources.addAll(this.sources);

returnCollections.unmodifiableSet(allSources);

這里組裝了引導類和自定義的source

2.4.4、加載

protectedvoidload(ApplicationContextcontext,Object[]sources){

if(logger.isDebugEnabled()){

logger.debug("Loadingsource"+StringUtils.arrayToCommaDelimitedString(sources));

//創(chuàng)建BeanDefinitionLoader

BeanDefinitionLoaderloader=createBeanDefinitionLoader(getBeanDefinitionRegistry(context),s