标签:SpringBoot args class listeners 详解 context new 原理 Class
一,本篇来说说SpringBoot的启动原理
打开启动类,调试进入可以发现SpirngBoot的启动分为两部分:
1创建SpringApplication对象
2运行Run方法
public static ConfigurableApplicationContext run(Class<?>[] primarySources, String[] args) {
return (new SpringApplication(primarySources)).run(args);
}
先从创建对象讲起
public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {
this.sources = new LinkedHashSet();
this.bannerMode = Mode.CONSOLE;
this.logStartupInfo = true;
this.addCommandLineProperties = true;
this.addConversionService = true;
this.headless = true;
this.registerShutdownHook = true;
this.additionalProfiles = new HashSet();
this.isCustomEnvironment = false;
this.lazyInitialization = false;
this.resourceLoader = resourceLoader;
Assert.notNull(primarySources, "PrimarySources must not be null");
this.primarySources = new LinkedHashSet(Arrays.asList(primarySources));
this.webApplicationType = WebApplicationType.deduceFromClasspath();
this.setInitializers(this.getSpringFactoriesInstances(ApplicationContextInitializer.class));
this.setListeners(this.getSpringFactoriesInstances(ApplicationListener.class));
this.mainApplicationClass = this.deduceMainApplicationClass();
}
上面即是SpringApplication对象的创建过程
主要看最后面三行(其他代码主要是一些属性设置)
this.setInitializers(this.getSpringFactoriesInstances(ApplicationContextInitializer.class));
---->
调试依次进入
this.getSpringFactoriesInstances()
loadFactoryNames()
loadSpringFactories()
classLoader.getResources(FACTORIES_RESOURCE_LOCATION);
点击FACTORIES_RESOURCE_LOCATION即可有如下发现
FACTORIES_RESOURCE_LOCATION = "META-INF/spring.factories";
总结,通过getSpringFactoriesInstances()方法从类路径META-INF/spring.factories找到所有的ApplicationContextinitializer然后保存起来
同理第二个,同样是通过getSpringFactoriesInstances()方法从类路径下找到所有的SpringApplicationRunListeners
this.setListeners(this.getSpringFactoriesInstances(ApplicationListener.class));
从获取的多个配置类中,找到配置主类(且主配置类可配置多个),并返回,至此,SpringApplication对象就创建完成了
this.mainApplicationClass = this.deduceMainApplicationClass();
----->
//从获取的多个配置类中,找到包含main方法的主配置类,然后返回
for(int var4 = 0; var4 < var3; ++var4) {
StackTraceElement stackTraceElement = var2[var4];
if ("main".equals(stackTraceElement.getMethodName())) {
return Class.forName(stackTraceElement.getClassName());
}
//可配置多个主配置类
public static ConfigurableApplicationContext run(Class<?>[] primarySources, String[] args) {
return (new SpringApplication(primarySources)).run(args);
}
第二步,运行run方法
public ConfigurableApplicationContext run(String... args) {
StopWatch stopWatch = new StopWatch();
stopWatch.start();
ConfigurableApplicationContext context = null;
Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList();
//配置与AWT应用相关的配置
/*
private void configureHeadlessProperty() {
System.setProperty("java.awt.headless", System.getProperty("java.awt.headless", Boolean.toString(this.headless)));
}
*/
this.configureHeadlessProperty();
//获取SpringApplicationRunListeners监听器
/*
private SpringApplicationRunListeners getRunListeners(String[] args) {
Class<?>[] types = new Class[]{SpringApplication.class, String[].class};
return new SpringApplicationRunListeners(logger, this.getSpringFactoriesInstances(SpringApplicationRunListener.class, types, this, args));
}*/
SpringApplicationRunListeners listeners = this.getRunListeners(args);
//回调获取所有的SpringApplicationRunListener并执行starting方法
listeners.starting();
//用来做异常报告分析
Collection exceptionReporters;
try {
//封装命令行参数
ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
//准备环境,
/*
获取所有的SpringApplicationRunListener并回调environmentPrepared()方法 listeners.environmentPrepared((ConfigurableEnvironment)environment);
*/
ConfigurableEnvironment environment = this.prepareEnvironment(listeners, applicationArguments);
this.configureIgnoreBeanInfo(environment);
//此处会在控制台打印Spring
Banner printedBanner = this.printBanner(environment);
//创建IOC容器
/*
1确定对于的IOC容器
2利用反射创建对应的IOC容器
protected ConfigurableApplicationContext createApplicationContext() {
Class<?> contextClass = this.applicationContextClass;
if (contextClass == null) {
try {
switch(this.webApplicationType) {
case SERVLET:
contextClass = Class.forName("org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext");
break;
case REACTIVE:
contextClass = Class.forName("org.springframework.boot.web.reactive.context.AnnotationConfigReactiveWebServerApplicationContext");
break;
default:
contextClass = Class.forName("org.springframework.context.annotation.AnnotationConfigApplicationContext");
}
} catch (ClassNotFoundException var3) {
throw new IllegalStateException("Unable create a default ApplicationContext, please specify an ApplicationContextClass", var3);
}
}
return (ConfigurableApplicationContext)BeanUtils.instantiateClass(contextClass);
}
*/
context = this.createApplicationContext();
//用来做异常分析报告
exceptionReporters = this.getSpringFactoriesInstances(SpringBootExceptionReporter.class, new Class[]{ConfigurableApplicationContext.class}, context);
//准备上下文环境,将environment加入到IOC容器中
/*
1 回调之前保存的所有的ApplicationContextInitializer的initialize方法初始
this.applyInitializers(context);
---->
protected void applyInitializers(ConfigurableApplicationContext context) {
Iterator var2 = this.getInitializers().iterator();
while(var2.hasNext()) {
ApplicationContextInitializer initializer = (ApplicationContextInitializer)var2.next();
Class<?> requiredType = GenericTypeResolver.resolveTypeArgument(initializer.getClass(), ApplicationContextInitializer.class);
Assert.isInstanceOf(requiredType, context, "Unable to call initializer.");
initializer.initialize(context);
}
####################
//2回调之前保存的所有的SpringApplicationRunListener的contextPrepared方法
listeners.contextPrepared(context);
----->
void contextPrepared(ConfigurableApplicationContext context) {
Iterator var2 = this.listeners.iterator();
while(var2.hasNext()) {
SpringApplicationRunListener listener = (SpringApplicationRunListener)var2.next();
listener.contextPrepared(context);
}
}
3最后SpringApplicationRunListener监听对象执行contextLoaded方法代表容器加载完成
*/
this.prepareContext(context, environment, listeners, applicationArguments, printedBanner);
//刷新容器,IOC容器的初始化过程,加载所有的组件,且Web
// 应用也是在此处加载嵌入式Tomcat容器
this.refreshContext(context);
//空方法
this.afterRefresh(context, applicationArguments);
stopWatch.stop();
if (this.logStartupInfo) {
(new StartupInfoLogger(this.mainApplicationClass)).logStarted(this.getApplicationLog(), stopWatch);
}
listeners.started(context);
//从IOC容器中,获取ApplicationRunner和ComandLineRunner类
//并回调callRunner方法
/*
private void callRunner(ApplicationRunner runner, ApplicationArguments args) {
try {
runner.run(args);
} catch (Exception var4) {
throw new IllegalStateException("Failed to execute ApplicationRunner", var4);
}
}
运行该事件监听器
*/
this.callRunners(context, applicationArguments);
} catch (Throwable var10) {
this.handleRunFailure(context, var10, exceptionReporters, listeners);
throw new IllegalStateException(var10);
}
try {
//遍历SpringApplicationRunListenen,并回调方法running(),
listeners.running(context);
//返回IOC容器对象,SpringBoot应用启动
return context;
} catch (Throwable var9) {
this.handleRunFailure(context, var9, exceptionReporters, (SpringApplicationRunListeners)null);
throw new IllegalStateException(var9);
}
}
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标签:SpringBoot,args,class,listeners,详解,context,new,原理,Class 来源: https://blog.csdn.net/m0_37510446/article/details/104124701
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