springboot的启动源码流程（菜鸟笔记）

亦凉 2024-02-19 22:15 50阅读 0赞

### springboot的启动源码流程 ###

#### 1.几个重要的事件回调机制 ####

//放在类路劲下的META-INF/spring.factories文件中
    ApplicationContextInitializer
    ApplicationListener
    
    //先执行ApplicationRunner，再执行CommandLineRunner
    ApplicationRunner
    CommandLineRunner

#### 2.springboot.run(Main.class)分为两部分 ####

//首先spring容器的创建
    //执行容器的run方法
    new SpringApplication(primarySources).run(args);

#### 3.spring容器的创建 ####

public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {
        
        this.resourceLoader = resourceLoader;
        Assert.notNull(primarySources, "PrimarySources must not be null");
        //保存主配置类
        this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
        //判断是否是web应用
        this.webApplicationType = WebApplicationType.deduceFromClasspath();
        
        //从类路劲下找到\META-INF\spring.factories配置所有的ApplicationContextInitializer然后保存起来
        //getSpringFactoriesInstances
        //1.从META-INF/spring.factories文件中找实现了ApplicationContextInitializer接口的所有类
        	//1.1 实现类如下
            org.springframework.context.ApplicationContextInitializer=\
            org.springframework.boot.context.ConfigurationWarningsApplicationContextInitializer,\
            org.springframework.boot.context.ContextIdApplicationContextInitializer,\
            org.springframework.boot.context.config.DelegatingApplicationContextInitializer,\
            org.springframework.boot.web.context.ServerPortInfoApplicationContextInitializer
        //2.createSpringFactoriesInstances 获取到的全类名，通过反射创建实例
    	//3.保存ApplicationContextInitializer创建的实例
        setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
        
        
        //从类路劲下找到\META-INF\spring.factories配置所有实现了ApplicationListener接口的类
        //getSpringFactoriesInstances
        //1.从META-INF/spring.factories文件中找实现了ApplicationListener接口的所有类
        //1.1 实现类如下：
        	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.ConfigFileApplicationListener,\
            org.springframework.boot.context.config.DelegatingApplicationListener,\
            org.springframework.boot.context.logging.ClasspathLoggingApplicationListener,\
            org.springframework.boot.context.logging.LoggingApplicationListener,\
            org.springframework.boot.liquibase.LiquibaseServiceLocatorApplicationListener
        //2.createSpringFactoriesInstances 获取到的全类名，通过反射创建实例
    	//3.保存ApplicationListener创建的实例
        setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
        //从配置类中找到有main方法的主类
        this.mainApplicationClass = deduceMainApplicationClass();
    }

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![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTA4Nzk0MjA_size_16_color_FFFFFF_t_70 1]

#### 4.执行容器的run方法 ####

/**
    * Run the Spring application, creating and refreshing a new ApplicationContext
    * @param args the application arguments (usually passed from a Java main method)
    * @return a running {@link ApplicationContext}
    */
    public ConfigurableApplicationContext run(String... args) {
        
        //用来打印，方法执行的时间，
        //如：Started BootMasterApplication in 56.783 seconds (JVM running for 69.93)
        StopWatch stopWatch = new StopWatch();
        stopWatch.start();
        //1.申明ioc容器
        ConfigurableApplicationContext context = null;
        Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();
        //2.配置环境变量  java.awt.headless='true'
        configureHeadlessProperty();
        
        //3.在\META-INF\spring.factories中找实现类接口SpringApplicationRunListener的所有类，并依次创建类的实例
        SpringApplicationRunListeners listeners = getRunListeners(args);
        //4.回调SpringApplicationRunListener.starting();依次开启所有的监听器
        listeners.starting();
        try {
        
            //5.包装传入参数  在Idea工具中添加命令行参数，如username=zzhua password=1234
            ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
            
            //6.准备环境变量
            //6.1 获取或者创建环境，配置环境
            //6.2 回调SpringApplicationRunListener.environmentPrepared(environment);表示环境准备完成
            ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);
            //6.3 配置ignore 的Bean信息
            configureIgnoreBeanInfo(environment);
            //7.打印Banner
            Banner printedBanner = printBanner(environment);
            //8.创建ApplicationContext，决定创建web容器还是普通的ioc，反射技术
            context = createApplicationContext();
            //9.异常信息处理
            exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,
                                                             new Class[] {
         ConfigurableApplicationContext.class }, context);
            //10.准备上下文环境
            //10.1 将environment保存到ioc容器中
            //10.2 applyInitializers(),回调前面保存的所有的ApplicationContextInitializer实现类的initialize()方法
            //10.3 回调所有的SpringApplicationRunListener.contextPrepared()
            prepareContext(context, environment, listeners, applicationArguments, printedBanner);
            //11. spring容器的刷新 applicationContext).refresh(); 【如果是web应用还会创建嵌入式的Tomcat】。 其他章节已经整理
            refreshContext(context);
            
            //空方法，让子类实现
            afterRefresh(context, applicationArguments);
            //12.监控结束，并打印花费时间日志
            stopWatch.stop();
            if (this.logStartupInfo) {
        
                new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);
            }
            //13.所有的SpringApplicationRunListener回调started()方法，表示容器开启完成
            listeners.started(context);
            //14
            //14.1 在ioc容器中获取所有实现了ApplicationRunner和CommandLineRunner接口的类
            //14.2 先回调所有的ApplicationRunner.run()
            //14.3 再回调所有的CommandLineRunner.run()
            callRunners(context, applicationArguments);
        }catch (Throwable ex) {
        
            handleRunFailure(context, ex, exceptionReporters, listeners);
            throw new IllegalStateException(ex);
        }
    
        try {
        
            //回调SpringApplicationRunListener.running()
            listeners.running(context);
        }catch (Throwable ex) {
        
            handleRunFailure(context, ex, exceptionReporters, null);
            throw new IllegalStateException(ex);
        }
        //返回创建好的容器
        return context;
    }

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