Spring源码0. springboot启动流程以及源码剖析目录

目录

    1. 初始化SpringApplication实例

    2. 发布启动事件ApplicationStartingEvent

    3. 封装命令行参数DefaultApplicationArguments

    4. prepareEnvironment()准备环境

    5. printBanner()打印Banner

    6. createApplicationContext()创建应用上下文

    7. SpringBootExceptionReporter异常上报

    8. prepareContext()准备应用上下文

    9. refreshContext()刷新应用上下文

    10. 启动完成, 发布ApplicationStartedEvent, ApplicationReadyEvent事件

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前言

当我们使用springboot的时候, 我们只需要配置如下启动类, spring便可以配置所有的环境和上下文, 本文基于springboot2.1.3, 剖析spring的启动流程和原理

@SpringBootApplication
public class YanggxApplication {
    public static void main(String[] args) {
        //调用SpringApplication的run方法
        SpringApplication.run(YanggxApplication.class, args);
    }
}

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SpringApplication运行代码

SpringApplication整个启动流程大概分为10个重要的步骤, 将会在之后的文章中逐个步骤分析

public class SpringApplication {
    
    //SpringApplication.run方法
    public static ConfigurableApplicationContext run(Class[] primarySources,
            String[] args) {
        //步骤1. 初始化SpringApplication实例
        return new SpringApplication(primarySources).run(args);
    }

    /**
     * 启动Spring 应用
     * @param args YanggxApplication中main函数的参数
     */
    public ConfigurableApplicationContext run(String... args) {
        //实例化一个StopWatch实例, 监控项目运行时间
        StopWatch stopWatch = new StopWatch();
        stopWatch.start();
        //初始化Spring上下文和错误报告参数
        ConfigurableApplicationContext context = null;
        Collection exceptionReporters = new ArrayList<>();
        //配置headless,在没有显示器,鼠标,键盘的情况下,仍然可以调用显示,输入输出的方法
        configureHeadlessProperty();
    
        //步骤2.发布Spring启动事件
        //获取SpringApplicationRunListeners
        //listeners的监听器列表中只包含了一个EventPublishingRunListener对象
        SpringApplicationRunListeners listeners = getRunListeners(args);
    
        //调用SpringFactoriesLoader#starting方法,
        //最终调用EventPublishingRunListener#starting方法
        listeners.starting();
        
        try {
            //步骤3. 封装命令行参数DefaultApplicationArguments
            ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
            
            //步骤4. prepareEnvironment()准备环境
            ConfigurableEnvironment environment = prepareEnvironment(listeners,applicationArguments);
            configureIgnoreBeanInfo(environment);
            
            //步骤5: printBanner()打印Banner
            Banner printedBanner = printBanner(environment);
            
            //步骤6: createApplicationContext()创建应用上下文
            context = createApplicationContext();
            
            //步骤7: SpringBootExceptionReporter异常上报
            exceptionReporters = getSpringFactoriesInstances(
                    SpringBootExceptionReporter.class,
                    new Class[] { ConfigurableApplicationContext.class }, context);
            //步骤8: prepareContext()准备应用上下文
            prepareContext(context, environment, listeners, applicationArguments,printedBanner);
            
            //步骤9: refreshContext()刷新应用上下文
            refreshContext(context);
            
            //步骤10: 启动完成, 发布ApplicationStartedEvent, ApplicationReadyEvent事件
            afterRefresh(context, applicationArguments);
            stopWatch.stop();
            if (this.logStartupInfo) {
                new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(),stopWatch);
            }
            //发布ApplicationStartedEvent
            listeners.started(context);
            callRunners(context, applicationArguments);
        }
        catch (Throwable ex) {
            handleRunFailure(context, ex, exceptionReporters, listeners);
            throw new IllegalStateException(ex);
        }
    
        try {
            //发布ApplicationReadyEvent事件
            listeners.running(context);
        }
        catch (Throwable ex) {
            handleRunFailure(context, ex, exceptionReporters, null);
            throw new IllegalStateException(ex);
        }
        return context;
    }
}