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1. SpringBoot中怎么启动Tomcat?
1.1 ServletWebServerFactoryAutoConfiguration
配置Servlet web容器。
@Configuration(proxyBeanMethods = false)
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)
@ConditionalOnClass(ServletRequest.class)
@ConditionalOnWebApplication(type = Type.SERVLET)
@EnableConfigurationProperties(ServerProperties.class)
@Import({ ServletWebServerFactoryAutoConfiguration.BeanPostProcessorsRegistrar.class,
ServletWebServerFactoryConfiguration.EmbeddedTomcat.class,
ServletWebServerFactoryConfiguration.EmbeddedJetty.class,
ServletWebServerFactoryConfiguration.EmbeddedUndertow.class })
public class ServletWebServerFactoryAutoConfiguration {
}
- ServletWebServerFactoryAutoConfiguration.BeanPostProcessorsRegistrar.class 导入
WebServerFactoryCustomizerBeanPostProcessor组件，web服务工厂定制器的后置增强 - 导入了三种不同的web服务器（Tomcat、Jetty、Undertow），默认是Tomcat
我们来看一下 EmbeddedTomcat:
@Configuration(proxyBeanMethods = false)
class ServletWebServerFactoryConfiguration {
@Configuration(proxyBeanMethods = false)
@ConditionalOnClass({ Servlet.class, Tomcat.class, UpgradeProtocol.class })
@ConditionalOnMissingBean(value = ServletWebServerFactory.class, search = SearchStrategy.CURRENT)
static class EmbeddedTomcat {
@Bean
TomcatServletWebServerFactory tomcatServletWebServerFactory(
ObjectProvider<TomcatConnectorCustomizer> connectorCustomizers,
ObjectProvider<TomcatContextCustomizer> contextCustomizers,
ObjectProvider<TomcatProtocolHandlerCustomizer<?>> protocolHandlerCustomizers) {
TomcatServletWebServerFactory factory = new TomcatServletWebServerFactory();
factory.getTomcatConnectorCustomizers()
.addAll(connectorCustomizers.orderedStream().collect(Collectors.toList()));
factory.getTomcatContextCustomizers()
.addAll(contextCustomizers.orderedStream().collect(Collectors.toList()));
factory.getTomcatProtocolHandlerCustomizers()
.addAll(protocolHandlerCustomizers.orderedStream().collect(Collectors.toList()));
return factory;
}
}
}
tomcatServletWebServerFactory()方法中的参数都是从容器中获取，我们可以自定义直接放到容器中。实现ServletWebServerFactory接口,该接口的getWebServlet()方法就是创建 Tomcat容器。
1.2 DispatcherServletAutoConfiguration
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)
@Configuration(proxyBeanMethods = false)
@ConditionalOnWebApplication(type = Type.SERVLET)
@ConditionalOnClass(DispatcherServlet.class)
@AutoConfigureAfter(ServletWebServerFactoryAutoConfiguration.class)
public class DispatcherServletAutoConfiguration {
public static final String DEFAULT_DISPATCHER_SERVLET_BEAN_NAME = "dispatcherServlet";
public static final String DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME = "dispatcherServletRegistration";
@Configuration(proxyBeanMethods = false)
@Conditional(DefaultDispatcherServletCondition.class)
@ConditionalOnClass(ServletRegistration.class)
@EnableConfigurationProperties(WebMvcProperties.class)
protected static class DispatcherServletConfiguration {
@Bean(name = DEFAULT_DISPATCHER_SERVLET_BEAN_NAME)
public DispatcherServlet dispatcherServlet(WebMvcProperties webMvcProperties) {
DispatcherServlet dispatcherServlet = new DispatcherServlet();
dispatcherServlet.setDispatchOptionsRequest(webMvcProperties.isDispatchOptionsRequest());
dispatcherServlet.setDispatchTraceRequest(webMvcProperties.isDispatchTraceRequest());
dispatcherServlet.setThrowExceptionIfNoHandlerFound(webMvcProperties.isThrowExceptionIfNoHandlerFound());
dispatcherServlet.setPublishEvents(webMvcProperties.isPublishRequestHandledEvents());
dispatcherServlet.setEnableLoggingRequestDetails(webMvcProperties.isLogRequestDetails());
return dispatcherServlet;
}
@Bean
@ConditionalOnBean(MultipartResolver.class)
@ConditionalOnMissingBean(name = DispatcherServlet.MULTIPART_RESOLVER_BEAN_NAME)
public MultipartResolver multipartResolver(MultipartResolver resolver) {
// Detect if the user has created a MultipartResolver but named it incorrectly
return resolver;
}
}
@Configuration(proxyBeanMethods = false)
@Conditional(DispatcherServletRegistrationCondition.class)
@ConditionalOnClass(ServletRegistration.class)
@EnableConfigurationProperties(WebMvcProperties.class)
@Import(DispatcherServletConfiguration.class)
protected static class DispatcherServletRegistrationConfiguration {
@Bean(name = DEFAULT_DISPATCHER_SERVLET_REGISTRATION_BEAN_NAME)
@ConditionalOnBean(value = DispatcherServlet.class, name = DEFAULT_DISPATCHER_SERVLET_BEAN_NAME)
public DispatcherServletRegistrationBean dispatcherServletRegistration(DispatcherServlet dispatcherServlet,
WebMvcProperties webMvcProperties, ObjectProvider<MultipartConfigElement> multipartConfig) {
DispatcherServletRegistrationBean registration = new DispatcherServletRegistrationBean(dispatcherServlet,
webMvcProperties.getServlet().getPath());
registration.setName(DEFAULT_DISPATCHER_SERVLET_BEAN_NAME);
registration.setLoadOnStartup(webMvcProperties.getServlet().getLoadOnStartup());
multipartConfig.ifAvailable(registration::setMultipartConfig);
return registration;
}
}
}
dispatcherServlet方法就是往容器中注入DispatcherServlet组件。- dispatcherServletRegistration() 方法就是将将
DispatcherServlet组件添加到Tomcat中（tomcat.addServlet()）
我们来看一下DispatcherServletRegistrationBean继承图：
在Tomcat启动的时候 会调用 ServletContextInitializer.onStartup() 方法回调，将DispatcherServlet 添加到 Tomcat中，后面的启动流程就跟SpringMVC的启动流程是一样的，参见Spring5源码14-SpringMVC入口及启动流程。
2. 核心方法run()
下面是一个简单的项目，我们直接开始看run方法
@SpringBootApplication
public class SpringbootDemoApplication {
public static void main(String[] args) {
ConfigurableApplicationContext run = SpringApplication.run(SpringbootDemoApplication.class, args);
Object demoService = run.getBean("demoService");
System.out.println("demoService = " + demoService);
}
}
我们这里直接看 SpringApplication#run(java.lang.Class<?>[], java.lang.String[])方法:
public static ConfigurableApplicationContext run(Class<?>[] primarySources, String[] args) {
return new SpringApplication(primarySources).run(args);
}
我们这里先看一下 SpringApplication 的构造函数流程:
public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {
this.resourceLoader = resourceLoader;
Assert.notNull(primarySources, "PrimarySources must not be null");
// 保存启动类信息
this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
// 初始化环境。环境分为三种 非web环境、web环境、reactive环境三种。其判断逻辑就是判断是否存在指定的类，默认是Servlet 环境，我们这也是Servlet
this.webApplicationType = WebApplicationType.deduceFromClasspath();
// getSpringFactoriesInstances 方法加载了 spring.factories文件。在这里进行了首次加载spring.factoies文件。设置 ApplicationContextInitializer
setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
// 获取监听器，也加载了spring.factories文件
setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
// 设置启动类信息
this.mainApplicationClass = deduceMainApplicationClass();
}
我们下面直接来看 SpringApplication#run(java.lang.String...) 方法的执行流程:
public ConfigurableApplicationContext run(String... args) {
// 开启关于启动时间的信息监控
StopWatch stopWatch = new StopWatch();
stopWatch.start();
// 准备 ApplicationContext
ConfigurableApplicationContext context = null;
Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();
//java.awt.headless是J2SE的一种模式用于在缺少显示屏、键盘或者鼠标时的系统配置，很多监控工具如jconsole 需要将该值设置为true，系统变量默认为true
configureHeadlessProperty();
// 1. 获取Spring的监听器类，这里是从 spring.factories 中去获取，默认的是以 org.springframework.boot.SpringApplicationRunListener 为key,获取到的监听器类型为 EventPublishingRunListener。
SpringApplicationRunListeners listeners = getRunListeners(args);
// 1.1 监听器发送启动事件
listeners.starting();
try {
// 封装参数
ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
// 2. 构造容器环境。将容器的一些配置内容加载到 environment 中
ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);
// 配置BeanInfo的忽略 ：“spring.beaninfo.ignore”，值为“true”表示跳过对BeanInfo类的搜索
configureIgnoreBeanInfo(environment);
// 打印信息对象
Banner printedBanner = printBanner(environment);
// 3. 创建上下文对象
context = createApplicationContext();
// 从 spring.factries 中获取错误报告的类。出错的时候会调用其方法通知
exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,
new Class[] { ConfigurableApplicationContext.class }, context);
// 4. 准备刷新上下文
prepareContext(context, environment, listeners, applicationArguments, printedBanner);
// 5. 刷新上下文
refreshContext(context);
// 结束刷新，留待扩展功能，并未实现什么
afterRefresh(context, applicationArguments);
// 停止监听
stopWatch.stop();
if (this.logStartupInfo) {
new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);
}
// 监听器发送启动结束时间
listeners.started(context);
// 调用 ApplicationRunner 和 CommandLineRunner 对应的方法
callRunners(context, applicationArguments);
}
catch (Throwable ex) {
handleRunFailure(context, ex, exceptionReporters, listeners);
throw new IllegalStateException(ex);
}
try {
// 发送容器运行事件
listeners.running(context);
}
catch (Throwable ex) {
handleRunFailure(context, ex, exceptionReporters, null);
throw new IllegalStateException(ex);
}
return context;
}
3. run()流程步骤详解
下面我们重点分析几个步骤
3.1 获取监听器
这一步是从 spring.factories 文件中获取监听器集合，当有事件发生时调用监听器对应事件的方法。
默认的是以org.springframework.boot.SpringApplicationRunListener 为key,获取到的监听器类型为 EventPublishingRunListener。
SpringApplicationRunListeners listeners = getRunListeners(args);
其详细代码如下：
private SpringApplicationRunListeners getRunListeners(String[] args) {
Class<?>[] types = new Class<?>[] { SpringApplication.class, String[].class };
return new SpringApplicationRunListeners(logger,
getSpringFactoriesInstances(SpringApplicationRunListener.class, types, this, args));
}
这里需要注意的是 getSpringFactoriesInstances(SpringApplicationRunListener.class, types, this, args)返回的是一个Collection 类型。也就是说明在 SpringApplicationRunListeners并非代表一个监听器，而是保存了监听器集合，在默认情况下，仅有一个 EventPublishingRunListener。在 SpringApplicationRunListeners 类中也能看到，如下：
class SpringApplicationRunListeners {
private final Log log;
private final List<SpringApplicationRunListener> listeners;
SpringApplicationRunListeners(Log log, Collection<? extends SpringApplicationRunListener> listeners) {
this.log = log;
this.listeners = new ArrayList<>(listeners);
}
...
}
总结一下: Spring启动时，通过 spring.factories 文件中获取监听器集合。默认类型为 EventPublishingRunListener。在事件发生时，EventPublishingRunListener 会寻找容器中 ApplicationListener 的bean，并进行事件通知。详见Spring5源码12-监听器原理
3.2 环境变量的构造
这一步的作用就是加载一些配置文件的内容
ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);
其具体实现如下:
private ConfigurableEnvironment prepareEnvironment(SpringApplicationRunListeners listeners,
ApplicationArguments applicationArguments) {
// Create and configure the environment
// 获取或者创建 environment。这里获取类型是 StandardServletEnvironment
ConfigurableEnvironment environment = getOrCreateEnvironment();
// 将入参配置到环境配置中
configureEnvironment(environment, applicationArguments.getSourceArgs());
ConfigurationPropertySources.attach(environment);
// 发布环境准备事件。
listeners.environmentPrepared(environment);
bindToSpringApplication(environment);
if (!this.isCustomEnvironment) {
environment = new EnvironmentConverter(getClassLoader()).convertEnvironmentIfNecessary(environment,
deduceEnvironmentClass());
}
ConfigurationPropertySources.attach(environment);
return environment;
}
private Class<? extends StandardEnvironment> deduceEnvironmentClass() {
switch (this.webApplicationType) {
case SERVLET:
return StandardServletEnvironment.class;
case REACTIVE:
return StandardReactiveWebEnvironment.class;
default:
return StandardEnvironment.class;
}
}
关于 webApplicationType 的值，在 org.springframework.boot.SpringApplication#SpringApplication(org.springframework.core.io.ResourceLoader, java.lang.Class<?>...) 构造函数中进行了赋值为Servlet。所以我们这里可以知道 Environment 类型为 StandardServletEnvironment 。
在 listeners.environmentPrepared(environment); 时会发送环境准备事件，环境准备事件要通知监听器如下。对于 Springboot 的配置文件application.yml或者application.properties文件的加载实际上是通过发布环境准备事件完成的，完成这项功能的就是ConfigDataEnvironmentPostProcessor。
3.2.1 application.yml 的加载
SpringBoot在启动时，读取所有的ApplicationListener下的配置类。spring-boot工程下的spring.factories文件：
# Application Listeners
org.springframework.context.ApplicationListener=\
org.springframework.boot.ClearCachesApplicationListener,\
org.springframework.boot.builder.ParentContextCloserApplicationListener,\
org.springframework.boot.context.FileEncodingApplicationListener,\
org.springframework.boot.context.config.AnsiOutputApplicationListener,\
org.springframework.boot.context.config.DelegatingApplicationListener,\
org.springframework.boot.context.logging.LoggingApplicationListener,\
org.springframework.boot.env.EnvironmentPostProcessorApplicationListener
当EnvironmentPostProcessorApplicationListener类接收到ApplicationEnvironmentPreparedEvent的事件时，就会调用EnvironmentPostProcessorsFactory类下的getEnvironmentPostProcessors方法来获取所有的EnvironmentPostProcessor下的配置类，并触发这些类的postProcessEnvironment方法。
public class EnvironmentPostProcessorApplicationListener implements SmartApplicationListener, Ordered {
...
public EnvironmentPostProcessorApplicationListener() {
this(EnvironmentPostProcessorsFactory::fromSpringFactories, new DeferredLogs());
}
@Override
public void onApplicationEvent(ApplicationEvent event) {
if (event instanceof ApplicationEnvironmentPreparedEvent) {
onApplicationEnvironmentPreparedEvent((ApplicationEnvironmentPreparedEvent) event);
}
...
}
private void onApplicationEnvironmentPreparedEvent(ApplicationEnvironmentPreparedEvent event) {
...
for (EnvironmentPostProcessor postProcessor : getEnvironmentPostProcessors(application.getResourceLoader(),
event.getBootstrapContext())) {
postProcessor.postProcessEnvironment(environment, application);
}
}
List<EnvironmentPostProcessor> getEnvironmentPostProcessors(ResourceLoader resourceLoader,
ConfigurableBootstrapContext bootstrapContext) {
...
EnvironmentPostProcessorsFactory postProcessorsFactory = this.postProcessorsFactory.apply(classLoader);
return postProcessorsFactory.getEnvironmentPostProcessors(this.deferredLogs, bootstrapContext);
}
}
@FunctionalInterface
public interface EnvironmentPostProcessorsFactory {
List<EnvironmentPostProcessor> getEnvironmentPostProcessors(DeferredLogFactory logFactory,
ConfigurableBootstrapContext bootstrapContext);
static EnvironmentPostProcessorsFactory fromSpringFactories(ClassLoader classLoader) {
return new ReflectionEnvironmentPostProcessorsFactory(classLoader,
SpringFactoriesLoader.loadFactoryNames(EnvironmentPostProcessor.class, classLoader));
}
spring.factories文件中 ：
# Environment Post Processors
org.springframework.boot.env.EnvironmentPostProcessor=\
org.springframework.boot.cloud.CloudFoundryVcapEnvironmentPostProcessor,\
org.springframework.boot.context.config.ConfigDataEnvironmentPostProcessor,\
org.springframework.boot.env.RandomValuePropertySourceEnvironmentPostProcessor,\
org.springframework.boot.env.SpringApplicationJsonEnvironmentPostProcessor,\
org.springframework.boot.env.SystemEnvironmentPropertySourceEnvironmentPostProcessor,\
org.springframework.boot.reactor.DebugAgentEnvironmentPostProcessor
EnvironmentPostProcessor
EnvironmentPostProcessor是处理程序的配置的，不同的子类实现不同的配置，有处理json配置文件的、有处理yaml配置文件的、有替换配置文件中的环境变量的。
- SpringBoot 2.4.0之前的版本，处理yaml配置文件的类是ConfigFileApplicationListener类
- SpringBoot 2.4.0之后的版本，处理yaml配置文件的类是ConfigDataEnvironmentPostProcessor类,我们重点看这个。
ConfigDataEnvironmentPostProcessor
SpringBoot 2.4.0之后的版本，使用ConfigDataEnvironmentPostProcessor 类来加载yaml文件中的配置。
public class ConfigDataEnvironmentPostProcessor implements EnvironmentPostProcessor, Ordered {
@Override
public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) {
postProcessEnvironment(environment, application.getResourceLoader(), application.getAdditionalProfiles());
}
void postProcessEnvironment(ConfigurableEnvironment environment, ResourceLoader resourceLoader,
Collection<String> additionalProfiles) {
...
getConfigDataEnvironment(environment, resourceLoader, additionalProfiles).processAndApply();
...
}
ConfigDataEnvironment getConfigDataEnvironment(ConfigurableEnvironment environment, ResourceLoader resourceLoader, Collection<String> additionalProfiles) {
return new ConfigDataEnvironment(this.logFactory, this.bootstrapContext, environment, resourceLoader, additionalProfiles, this.environmentUpdateListener);
}
}
ConfigDataEnvironment
ConfigDataEnvironmentPostProcessor 在postProcessEnvironment方法中会实例化一个ConfigDataEnvironment对象，这个对象会加载optional:classpath:/;optional:classpath:/config/;optional:file:./;optional:file:./config/;optional:file:./config/*/路径下的yaml文件。
class ConfigDataEnvironment {
static final String LOCATION_PROPERTY = "spring.config.location";
static final String ADDITIONAL_LOCATION_PROPERTY = "spring.config.additional-location";
static final String IMPORT_PROPERTY = "spring.config.import";
static final ConfigDataLocation[] DEFAULT_SEARCH_LOCATIONS;
static {
List<ConfigDataLocation> locations = new ArrayList<>();
locations.add(ConfigDataLocation.of("optional:classpath:/;optional:classpath:/config/"));
locations.add(ConfigDataLocation.of("optional:file:./;optional:file:./config/;optional:file:./config/*/"));
DEFAULT_SEARCH_LOCATIONS = locations.toArray(new ConfigDataLocation[0]);
}
private ConfigDataEnvironmentContributors createContributors(Binder binder) {
...
contributors.addAll(getInitialImportContributors(binder));
...
return createContributors(contributors);
}
protected ConfigDataEnvironmentContributors createContributors(
List<ConfigDataEnvironmentContributor> contributors) {
return new ConfigDataEnvironmentContributors(this.logFactory, this.bootstrapContext, contributors);
}
private List<ConfigDataEnvironmentContributor> getInitialImportContributors(Binder binder) {
List<ConfigDataEnvironmentContributor> initialContributors = new ArrayList<>();
addInitialImportContributors(initialContributors, bindLocations(binder, IMPORT_PROPERTY, EMPTY_LOCATIONS));
addInitialImportContributors(initialContributors,
bindLocations(binder, ADDITIONAL_LOCATION_PROPERTY, EMPTY_LOCATIONS));
addInitialImportContributors(initialContributors,
bindLocations(binder, LOCATION_PROPERTY, DEFAULT_SEARCH_LOCATIONS));
return initialContributors;
}
}
spring.factories文件中 ：
# ConfigData Location Resolvers
org.springframework.boot.context.config.ConfigDataLocationResolver=\
org.springframework.boot.context.config.ConfigTreeConfigDataLocationResolver,\
org.springframework.boot.context.config.StandardConfigDataLocationResolver
# ConfigData Loaders
org.springframework.boot.context.config.ConfigDataLoader=\
org.springframework.boot.context.config.ConfigTreeConfigDataLoader,\
org.springframework.boot.context.config.StandardConfigDataLoader
# PropertySource Loaders
org.springframework.boot.env.PropertySourceLoader=\
org.springframework.boot.env.PropertiesPropertySourceLoader,\
org.springframework.boot.env.YamlPropertySourceLoader
processAndApply()
请求路径为：processAndApply() -> ConfigDataEnvironment#processAndApply -> ConfigDataEnvironment#processWithoutProfiles -> ConfigDataEnvironmentContributors#withProcessedImports -> ConfigDataImporter#resolveAndLoad -> ConfigDataImporter#load -> ConfigDataLoaders#load -> StandardConfigDataLoader#load -> YamlPropertySourceLoader#load
我们直接看YamlPropertySourceLoader#load 方法：
public class YamlPropertySourceLoader implements PropertySourceLoader {
@Override
public String[] getFileExtensions() {
return new String[] { "yml", "yaml" };
}
@Override
public List<PropertySource<?>> load(String name, Resource resource) throws IOException {
if (!ClassUtils.isPresent("org.yaml.snakeyaml.Yaml", getClass().getClassLoader())) {
throw new IllegalStateException(
"Attempted to load " + name + " but snakeyaml was not found on the classpath");
}
List<Map<String, Object>> loaded = new OriginTrackedYamlLoader(resource).load();
if (loaded.isEmpty()) {
return Collections.emptyList();
}
List<PropertySource<?>> propertySources = new ArrayList<>(loaded.size());
for (int i = 0; i < loaded.size(); i++) {
String documentNumber = (loaded.size() != 1) ? " (document #" + i + ")" : "";
propertySources.add(new OriginTrackedMapPropertySource(name + documentNumber,
Collections.unmodifiableMap(loaded.get(i)), true));
}
return propertySources;
}
}
在这里加载 application.yml文件。
EnvironmentPostProcessor
如果想处理加载的配置文件，可以在自己的java项目里添加spring.factories，然后实现EnvironmentPostProcessor类。
org.springframework.boot.env.EnvironmentPostProcessor=\
com.camellibby.springboot.component.DemoEnvironmentPostProcessor
public class DemoEnvironmentPostProcessor implements EnvironmentPostProcessor {
@Override
public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) {
System.out.println("DemoEnvironmentPostProcessor is starting");
}
}
3.3 创建上下文
这一步是创建上下文了:
context = createApplicationContext();
其详细内容如下：
public static final String DEFAULT_CONTEXT_CLASS = "org.springframework.context."
+ "annotation.AnnotationConfigApplicationContext";
public static final String DEFAULT_SERVLET_WEB_CONTEXT_CLASS = "org.springframework.boot."
+ "web.servlet.context.AnnotationConfigServletWebServerApplicationContext";
public static final String DEFAULT_REACTIVE_WEB_CONTEXT_CLASS = "org.springframework."
+ "boot.web.reactive.context.AnnotationConfigReactiveWebServerApplicationContext";
protected ConfigurableApplicationContext createApplicationContext() {
return this.applicationContextFactory.create(this.webApplicationType);
}
// org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext.Factory#create
static class Factory implements ApplicationContextFactory {
@Override
public ConfigurableApplicationContext create(WebApplicationType webApplicationType) {
return (webApplicationType != WebApplicationType.SERVLET) ? null
: new AnnotationConfigServletWebServerApplicationContext();
}
}
public AnnotationConfigServletWebServerApplicationContext() {
this.reader = new AnnotatedBeanDefinitionReader(this);
this.scanner = new ClassPathBeanDefinitionScanner(this);
}
很明显，因为我们知道 webApplicationType 值是 servlet，所以这里创建的是 AnnotationConfigServletWebServerApplicationContext 类型的上下文
这里需要注意：AnnotationConfigServletWebServerApplicationContext 构造函数中会创建 AnnotatedBeanDefinitionReader。而在 AnnotatedBeanDefinitionReader 构造函数中会调用 AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry);，该方法将一些必要Bean(如ConfigurationClassPostProcessor、AutowiredAnnotationBeanPostProcessor、CommonAnnotationBeanPostProcessor 等)注入到了容器中。
3.4 上下文准备工作
上面一步，仅仅是将上下文创建出来了，并没有对上下文进行操作。这一步开始对上下文的准备操作。
prepareContext(context, environment, listeners, applicationArguments, printedBanner);
其详细内容如下：
private void prepareContext(ConfigurableApplicationContext context, ConfigurableEnvironment environment,
SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments, Banner printedBanner) {
// 设置上下文的环境变量
context.setEnvironment(environment);
// 执行容器后置处理 ： 可以注册beanName策略生成器、设置资源加载器，设置转换服务等。但这里默认是没有做任何处理。目的是留给后续可以扩展
postProcessApplicationContext(context);
// 处理所有的初始化类的初始化方法。即 spring.factories 中key 为 org.springframework.context.ApplicationContextInitializer 指向的类，调用其 initialize 方法
applyInitializers(context);
// 向监听器发送容器准备事件
listeners.contextPrepared(context);
if (this.logStartupInfo) {
logStartupInfo(context.getParent() == null);
logStartupProfileInfo(context);
}
// Add boot specific singleton beans
// 获取上下文中的 BeanFactory。这里的BeanFactory 实际类型是 DefaultListableBeanFactory。BeanFactory 在初始化的时候，直接在构造函数里创建为 DefaultListableBeanFactory
ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
// 注册 springApplicationArguments等一系列bean
beanFactory.registerSingleton("springApplicationArguments", applicationArguments);
if (printedBanner != null) {
beanFactory.registerSingleton("springBootBanner", printedBanner);
}
if (beanFactory instanceof DefaultListableBeanFactory) {
// 设置是否允许bean定义覆盖
((DefaultListableBeanFactory) beanFactory)
.setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
}
// 如果允许懒加载，则添加对应的BeanFactory后置处理器
if (this.lazyInitialization) {
context.addBeanFactoryPostProcessor(new LazyInitializationBeanFactoryPostProcessor());
}
// Load the sources
// 这里加载的实际上是启动类
Set<Object> sources = getAllSources();
Assert.notEmpty(sources, "Sources must not be empty");
// 这里将启动类加入到 beanDefinitionMap 中，为后续的自动化配置做好了基础
load(context, sources.toArray(new Object[0]));
// 发送容器加载完成事件
listeners.contextLoaded(context);
}
....
// 需要注意这里的 sources参数实际上是 启动类的 Class
protected void load(ApplicationContext context, Object[] sources) {
if (logger.isDebugEnabled()) {
logger.debug("Loading source " + StringUtils.arrayToCommaDelimitedString(sources));
}
// 从上下文中获取 BeanDefinitionRegistry并依次创建出 BeanDefinitionLoader 。这里将sources作为参数保存到了 loader 中。也就是 loader 中保存了 启动类的Class信息
BeanDefinitionLoader loader = createBeanDefinitionLoader(getBeanDefinitionRegistry(context), sources);
if (this.beanNameGenerator != null) {
loader.setBeanNameGenerator(this.beanNameGenerator);
}
if (this.resourceLoader != null) {
loader.setResourceLoader(this.resourceLoader);
}
if (this.environment != null) {
loader.setEnvironment(this.environment);
}
loader.load();
}
我们这里比较关键的方法是 loader.load(); 方法 其中 loader.load(); 不管怎么跳转，最后都会跳转到 BeanDefinitionLoader#load(java.lang.Class<?>) 方法中。如下:
private int load(Class<?> source) {
// 判断是否存在 groovy 加载方式
if (isGroovyPresent() && GroovyBeanDefinitionSource.class.isAssignableFrom(source)) {
// Any GroovyLoaders added in beans{} DSL can contribute beans here
GroovyBeanDefinitionSource loader = BeanUtils.instantiateClass(source, GroovyBeanDefinitionSource.class);
load(loader);
}
// 判断 source 是否 需要被加载到Spring容器中。实际上是根据判断是否存在 @Component
if (isComponent(source)) {
// 将source 就是启动类的 class，注册到 annotatedReader 中。annotatedReader 类型是AnnotatedBeanDefinitionReader。
this.annotatedReader.register(source);
return 1;
}
return 0;
}
this.annotatedReader.register(source); 后续会跳转到 AnnotatedBeanDefinitionReader#doRegisterBean 方法中，看名字就知道是这个方法的工作是注册 Bean。实际上，在这个方法中完成了对@Qualifier 以及一些其他注解的处理。具体如下：
// 这里的 beanClass 其实就是启动类的 beanClass
private <T> void doRegisterBean(Class<T> beanClass, @Nullable String name,
@Nullable Class<? extends Annotation>[] qualifiers, @Nullable Supplier<T> supplier,
@Nullable BeanDefinitionCustomizer[] customizers) {
// 将Class 转换成一个 BeanDefinition 类
AnnotatedGenericBeanDefinition abd = new AnnotatedGenericBeanDefinition(beanClass);
// 判断是否应该跳过
if (this.conditionEvaluator.shouldSkip(abd.getMetadata())) {
return;
}
abd.setInstanceSupplier(supplier);
// 保存其作用域信息。这里默认是 singleton
ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(abd);
abd.setScope(scopeMetadata.getScopeName());
// 获取 beanName
String beanName = (name != null ? name : this.beanNameGenerator.generateBeanName(abd, this.registry));
// 处理一些通用的注解信息，包括Lazy、Primary、DependsOn、Role、Description 注解。获取其value值并保存到 abd 中
AnnotationConfigUtils.processCommonDefinitionAnnotations(abd);
// 处理 @Qualifier
if (qualifiers != null) {
for (Class<? extends Annotation> qualifier : qualifiers) {
if (Primary.class == qualifier) {
abd.setPrimary(true);
}
else if (Lazy.class == qualifier) {
abd.setLazyInit(true);
}
else {
abd.addQualifier(new AutowireCandidateQualifier(qualifier));
}
}
}
if (customizers != null) {
for (BeanDefinitionCustomizer customizer : customizers) {
customizer.customize(abd);
}
}
BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(abd, beanName);
// 判断是否需要创建代理，需要则创建
definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
// 将 BeanDefinitionHolder 注册到 容器中。此时的 registry 就是 AnnotationConfigServletWebServerApplicationContext。在BeanDefinitionLoader 初始化的时候保存的
BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, this.registry);
}
3.5 SpringApplication#refreshContext
对容器进行一个刷新工作。在此进行了大量的工作。这里的处理工作就由Springboot交给 Spring来处理了
refreshContext(context);
详细如下:
private void refreshContext(ConfigurableApplicationContext context) {
refresh(context);
if (this.registerShutdownHook) {
try {
context.registerShutdownHook();
}
catch (AccessControlException ex) {
// Not allowed in some environments.
}
}
}
最终会跳转到 AbstractApplicationContext#refresh 中。而关于 AbstractApplicationContext#refresh 方法在之前的文章中有过介绍，参见Spring5源码11-容器刷新refresh方法(注解版)。我们重点看一下Tomcat的启动过程，着重看onRefresh()方法：
@Override
public void refresh() throws BeansException, IllegalStateException {
// Initialize other special beans in specific context subclasses.
onRefresh();
// Check for listener beans and register them.
registerListeners();
}
SpringBoot使用ServletWebServerApplicationContext#onRefresh：
@Override
protected void onRefresh() {
super.onRefresh();
try {
createWebServer();
}
catch (Throwable ex) {
throw new ApplicationContextException("Unable to start web server", ex);
}
}
直接看createWebServer()方法：
private void createWebServer() {
WebServer webServer = this.webServer;
ServletContext servletContext = getServletContext();
if (webServer == null && servletContext == null) {
StartupStep createWebServer = this.getApplicationStartup().start("spring.boot.webserver.create");
// 本文环境获取的是tomcatServletWebServerFactory，默认的
ServletWebServerFactory factory = getWebServerFactory();
createWebServer.tag("factory", factory.getClass().toString());
this.webServer = factory.getWebServer(getSelfInitializer());
createWebServer.end();
getBeanFactory().registerSingleton("webServerGracefulShutdown",
new WebServerGracefulShutdownLifecycle(this.webServer));
getBeanFactory().registerSingleton("webServerStartStop",
new WebServerStartStopLifecycle(this, this.webServer));
}
else if (servletContext != null) {
try {
getSelfInitializer().onStartup(servletContext);
}
catch (ServletException ex) {
throw new ApplicationContextException("Cannot initialize servlet context", ex);
}
}
initPropertySources();
}
3.5.1 getWebServerFactory()
如下所示，从容器中获取ServletWebServerFactory类型的bean，唯一一个，否则抛出异常。本文环境获取的是tomcatServletWebServerFactory。
protected ServletWebServerFactory getWebServerFactory() {
// Use bean names so that we don't consider the hierarchy
String[] beanNames = getBeanFactory().getBeanNamesForType(ServletWebServerFactory.class);
if (beanNames.length == 0) {
throw new ApplicationContextException("Unable to start ServletWebServerApplicationContext due to missing "
+ "ServletWebServerFactory bean.");
}
if (beanNames.length > 1) {
throw new ApplicationContextException("Unable to start ServletWebServerApplicationContext due to multiple "
+ "ServletWebServerFactory beans : " + StringUtils.arrayToCommaDelimitedString(beanNames));
}
return getBeanFactory().getBean(beanNames[0], ServletWebServerFactory.class);
}
3.5.2 getSelfInitializer()
ServletWebServerApplicationContext的getSelfInitializer方法，返回的是ServletContextInitializer。
private org.springframework.boot.web.servlet.ServletContextInitializer getSelfInitializer() {
return this::selfInitialize;
}
看到this::selfInitialize是不是比较迷糊？典型的java8的lambda写法。我们看一下ServletContextInitializer 可能就明白了。
如下所示，其是一个函数式接口，只有一个onStartup方法。函数式接口(有且仅有一个抽象方法的接口)可以使用lambda式的写法。
@FunctionalInterface
public interface ServletContextInitializer {
// 初始化过程中，使用给定的servlets、filters、listeners
//context-params and attributes necessary配置ServletContext
void onStartup(ServletContext servletContext) throws ServletException;
}
我们这里获取到的本质是一个lambda，参数则是当前this，如下图所示：
this::selfInitialize中的selfInitialize则指的是ServletWebServerApplicationContext的selfInitialize方法。this指的是AnnotationConfigServletWebServerApplicationContext，其继承于ServletWebServerApplicationContext
private void selfInitialize(ServletContext servletContext) throws ServletException {
prepareWebApplicationContext(servletContext);
registerApplicationScope(servletContext);
WebApplicationContextUtils.registerEnvironmentBeans(getBeanFactory(), servletContext);
for (ServletContextInitializer beans : getServletContextInitializerBeans()) {
beans.onStartup(servletContext);
}
}
其实换成匿名类的写法则是：
new ServletContextInitializer() {
@Override
public void onStartup(ServletContext servletContext) throws ServletException {
selfInitialize(servletContext);
}
};
3.5.3 getWebServer(）
本文这里是TomcatServletWebServerFactory#getWebServer方法。
@Override
public WebServer getWebServer(ServletContextInitializer... initializers) {
if (this.disableMBeanRegistry) {
// registry = new NoDescriptorRegistry();
Registry.disableRegistry();
}
//实例化Tomcat
Tomcat tomcat = new Tomcat();
//获取临时路径
File baseDir = (this.baseDirectory != null) ? this.baseDirectory : createTempDir("tomcat");
//设置基础路径
tomcat.setBaseDir(baseDir.getAbsolutePath());
//实例化Connector 并进行配置
Connector connector = new Connector(this.protocol);
connector.setThrowOnFailure(true);
//这里会实例化server service
tomcat.getService().addConnector(connector);
customizeConnector(connector);
//对Connector做配置比如Protocol、URIEncoding
tomcat.setConnector(connector);
//这里会实例化Engine、Host
tomcat.getHost().setAutoDeploy(false);
configureEngine(tomcat.getEngine());
for (Connector additionalConnector : this.additionalTomcatConnectors) {
// todo
tomcat.getService().addConnector(additionalConnector);
}
prepareContext(tomcat.getHost(), initializers);
return getTomcatWebServer(tomcat);
}
getService
getService首先会触发getServer然后获取service。getServer如下所示会实例化Server并对其进行配置。
public Service getService() {
return getServer().findServices()[0];
}
public Server getServer() {
if (server != null) {
return server;
}
System.setProperty("catalina.useNaming", "false");
// 实例化 server
server = new StandardServer();
// 对basedir做处理
initBaseDir();
// Set configuration source
ConfigFileLoader.setSource(new CatalinaBaseConfigurationSource(new File(basedir), null));
// 为server设置port和service
server.setPort( -1 );
//实例化service
Service service = new StandardService();
service.setName("Tomcat");
server.addService(service);
return server;
}
prepareContext
这里会实例化TomcatEmbeddedContext并对其进行配置。
protected void prepareContext(Host host, ServletContextInitializer[] initializers) {
File documentRoot = getValidDocumentRoot();
TomcatEmbeddedContext context = new TomcatEmbeddedContext();
if (documentRoot != null) {
context.setResources(new LoaderHidingResourceRoot(context));
}
context.setName(getContextPath());
context.setDisplayName(getDisplayName());
context.setPath(getContextPath());
File docBase = (documentRoot != null) ? documentRoot : createTempDir("tomcat-docbase");
context.setDocBase(docBase.getAbsolutePath());
context.addLifecycleListener(new FixContextListener());
context.setParentClassLoader((this.resourceLoader != null) ? this.resourceLoader.getClassLoader()
: ClassUtils.getDefaultClassLoader());
resetDefaultLocaleMapping(context);
addLocaleMappings(context);
context.setUseRelativeRedirects(false);
try {
context.setCreateUploadTargets(true);
}
catch (NoSuchMethodError ex) {
// Tomcat is < 8.5.39. Continue.
}
configureTldSkipPatterns(context);
WebappLoader loader = new WebappLoader(context.getParentClassLoader());
loader.setLoaderClass(TomcatEmbeddedWebappClassLoader.class.getName());
loader.setDelegate(true);
context.setLoader(loader);
if (isRegisterDefaultServlet()) {
addDefaultServlet(context);
}
if (shouldRegisterJspServlet()) {
addJspServlet(context);
addJasperInitializer(context);
}
context.addLifecycleListener(new StaticResourceConfigurer(context));
ServletContextInitializer[] initializersToUse = mergeInitializers(initializers);
host.addChild(context);
configureContext(context, initializersToUse);
postProcessContext(context);
}
getTomcatWebServer
这个方法很简单，只是直接实例化了TomcatWebServer返回。其构造方法触发了initialize，这会引起后续一系列动作，包括tomcat.start()。
protected TomcatWebServer getTomcatWebServer(Tomcat tomcat) {
return new TomcatWebServer(tomcat, getPort() >= 0);
}
public TomcatWebServer(Tomcat tomcat, boolean autoStart) {
Assert.notNull(tomcat, "Tomcat Server must not be null");
this.tomcat = tomcat;
this.autoStart = autoStart;
// todo
initialize();
}
initialize()
我们回过头来，看一下initialize()方法：
private void initialize() throws WebServerException {
logger.info("Tomcat initialized with port(s): " + getPortsDescription(false));
synchronized (this.monitor) {
try {
...
// Start the server to trigger initialization listeners
this.tomcat.start();
...
}
}
}
在这里将嵌入式Tomcat启动。
selfInitialize
获取到TomcatWebServer后，Tomcat启动之后就触发了selfInitialize方法。这里servletContext其实是获取了ApplicationContext的一个门面/外观–ApplicationContextCade。
// ServletWebServerApplicationContext
private void selfInitialize(ServletContext servletContext) throws ServletException {
// todo
prepareWebApplicationContext(servletContext);
// todo
registerApplicationScope(servletContext);
// todo
WebApplicationContextUtils.registerEnvironmentBeans(getBeanFactory(), servletContext);
// todo
for (ServletContextInitializer beans : getServletContextInitializerBeans()) {
beans.onStartup(servletContext);
}
}
-
prepareWebApplicationContextServletWebServerApplicationContext的prepareWebApplicationContext方法如下所示，简单来讲就是为servletContext设置根容器属性并为当前应用上下文ApplicationContext设置servletContext引用。
protected void prepareWebApplicationContext(ServletContext servletContext) {
//尝试从servletContext中获取rootContext
Object rootContext = servletContext.getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);
if (rootContext != null) {
if (rootContext == this) {
throw new IllegalStateException(
"Cannot initialize context because there is already a root application context present - "
+ "check whether you have multiple ServletContextInitializers!");
}
return;
}
Log logger = LogFactory.getLog(ContextLoader.class);
// 这个日志是不是很熟悉？！
servletContext.log("Initializing Spring embedded WebApplicationContext");
try {
//向servletContext设置属性 ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE
servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, this);
if (logger.isDebugEnabled()) {
logger.debug("Published root WebApplicationContext as ServletContext attribute with name ["
+ WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE + "]");
}
// 为ApplicationContext设置servletContext引用
setServletContext(servletContext);
if (logger.isInfoEnabled()) {
long elapsedTime = System.currentTimeMillis() - getStartupDate();
logger.info("Root WebApplicationContext: initialization completed in " + elapsedTime + " ms");
}
}
catch (RuntimeException | Error ex) {
logger.error("Context initialization failed", ex);
servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, ex);
throw ex;
}
}
registerApplicationScope:ServletWebServerApplicationContext的registerApplicationScope方法如下所示，简单来讲就是(扩展)注册scope-application。这里会实例化一个ServletContextScope (包装了servletContext)，然后注册到BeanFactory中并为servletContext设置属性。
private void registerApplicationScope(ServletContext servletContext) {
ServletContextScope appScope = new ServletContextScope(servletContext);
// application
getBeanFactory().registerScope(WebApplicationContext.SCOPE_APPLICATION, appScope);
// Register as ServletContext attribute, for ContextCleanupListener to detect it.
servletContext.setAttribute(ServletContextScope.class.getName(), appScope);
}
我们在Spring中refresh分析之postProcessBeanFactory方法详解提到了request-RequestScope，session–SessionScope的注册，本文这里注册了application-ServletContextScope注册。
registerEnvironmentBeans:WebApplicationContextUtils的registerEnvironmentBeans方法。
public static void registerEnvironmentBeans(ConfigurableListableBeanFactory bf, @Nullable ServletContext sc) {
registerEnvironmentBeans(bf, sc, null);
}
public static void registerEnvironmentBeans(ConfigurableListableBeanFactory bf,
@Nullable ServletContext servletContext, @Nullable ServletConfig servletConfig) {
//将servletContext作为单例注册容器
if (servletContext != null && !bf.containsBean(WebApplicationContext.SERVLET_CONTEXT_BEAN_NAME)) {
bf.registerSingleton(WebApplicationContext.SERVLET_CONTEXT_BEAN_NAME, servletContext);
}
// 将servletConfig 作为单例注册容器本文这里没有触发
if (servletConfig != null && !bf.containsBean(ConfigurableWebApplicationContext.SERVLET_CONFIG_BEAN_NAME)) {
bf.registerSingleton(ConfigurableWebApplicationContext.SERVLET_CONFIG_BEAN_NAME, servletConfig);
}
// String CONTEXT_PARAMETERS_BEAN_NAME = "contextParameters";
if (!bf.containsBean(WebApplicationContext.CONTEXT_PARAMETERS_BEAN_NAME)) {
Map<String, String> parameterMap = new HashMap<>();
if (servletContext != null) {
// 获取servletContextd的初始化参数
Enumeration<?> paramNameEnum = servletContext.getInitParameterNames();
while (paramNameEnum.hasMoreElements()) {
String paramName = (String) paramNameEnum.nextElement();
parameterMap.put(paramName, servletContext.getInitParameter(paramName));
}
}
// 本文这里servletConfig 为null
if (servletConfig != null) {
// // 获取servletConfig的初始化参数
Enumeration<?> paramNameEnum = servletConfig.getInitParameterNames();
while (paramNameEnum.hasMoreElements()) {
String paramName = (String) paramNameEnum.nextElement();
parameterMap.put(paramName, servletConfig.getInitParameter(paramName));
}
}
// 将contextParameters作为单例注册到容器
bf.registerSingleton(WebApplicationContext.CONTEXT_PARAMETERS_BEAN_NAME,
Collections.unmodifiableMap(parameterMap));
}
// String CONTEXT_ATTRIBUTES_BEAN_NAME = "contextAttributes";
if (!bf.containsBean(WebApplicationContext.CONTEXT_ATTRIBUTES_BEAN_NAME)) {
Map<String, Object> attributeMap = new HashMap<>();
if (servletContext != null) {
Enumeration<?> attrNameEnum = servletContext.getAttributeNames();
while (attrNameEnum.hasMoreElements()) {
String attrName = (String) attrNameEnum.nextElement();
attributeMap.put(attrName, servletContext.getAttribute(attrName));
}
}
// 将contextAttributes作为单例注册到容器
bf.registerSingleton(WebApplicationContext.CONTEXT_ATTRIBUTES_BEAN_NAME,
Collections.unmodifiableMap(attributeMap));
}
}
- 触发
ServletContextInitializer的onStartup:如下所示，这里会获取ServletContextInitializer的所有实例，遍历触发其onStartup方法。
for (ServletContextInitializer beans : getServletContextInitializerBeans()) {
beans.onStartup(servletContext);
}
如下所示，将会挨个触发这5个的onStartup方法:
![202301012004229153.png][] 核心代码如下：
// org.springframework.boot.web.servlet.RegistrationBean#onStartup
@Override
public final void onStartup(ServletContext servletContext) throws ServletException {
String description = getDescription();
if (!isEnabled()) {
logger.info(StringUtils.capitalize(description) + " was not registered (disabled)");
return;
}
register(description, servletContext);
}
// org.springframework.boot.web.servlet.DynamicRegistrationBean#register
@Override
protected final void register(String description, ServletContext servletContext) {
D registration = addRegistration(description, servletContext);
if (registration == null) {
logger.info(StringUtils.capitalize(description) + " was not registered (possibly already registered?)");
return;
}
configure(registration);
}
// org.springframework.boot.web.servlet.ServletRegistrationBean#addRegistration
@Override
protected ServletRegistration.Dynamic addRegistration(String description, ServletContext servletContext) {
String name = getServletName();
return servletContext.addServlet(name, this.servlet);
}
在这里，`会将Dispatcher加入到Tomcat中`，之后就是Tomcat的启动流程，跟之前启动SpringMVC流程一样，参见：[Spring5源码14-SpringMVC入口及启动流程][Spring5_14-SpringMVC]
3.6 afterRefresh
进入org.springframework.boot.SpringApplication#afterRefresh方法中
protected void afterRefresh(ConfigurableApplicationContext context, ApplicationArguments args) {
}
这里啥也没做，就是一个模板方法，可能使用于扩展性的吧
3.7 callRunners
进入org.springframework.boot.SpringApplication#callRunners方法中
private void callRunners(ApplicationContext context, ApplicationArguments args) {
List<Object> runners = new ArrayList<>();
runners.addAll(context.getBeansOfType(ApplicationRunner.class).values());
runners.addAll(context.getBeansOfType(CommandLineRunner.class).values());
AnnotationAwareOrderComparator.sort(runners);
for (Object runner : new LinkedHashSet<>(runners)) {
if (runner instanceof ApplicationRunner) {
callRunner((ApplicationRunner) runner, args);
}
if (runner instanceof CommandLineRunner) {
callRunner((CommandLineRunner) runner, args);
}
}
}
private void callRunner(ApplicationRunner runner, ApplicationArguments args) {
try {
(runner).run(args);
}
catch (Exception ex) {
throw new IllegalStateException("Failed to execute ApplicationRunner", ex);
}
}
可以看到这里主要就是从容器中获取runner对象并调用对应的run方法。
3.8 流程框图
参考文章
Spring5源码注释github地址
Spring源码深度解析（第2版）
spring源码解析
Spring源码深度解析笔记
Spring注解与源码分析
Spring注解驱动开发B站教程