springboot运行原理（下）

曾经终败给现在 2022-11-30 12:42 169阅读 0赞

> ## 福兮祸所伏，祸兮福所倚 ##

接着上篇来说  springboot运行主要做了两件事  1.new  SpringApplication对象  2.调用了run方法   上篇已经把new  SpringApplication对象说清楚了  下面咱们来看看run方法到底做了  上源码

public ConfigurableApplicationContext run(String... args) {
            // 
            StopWatch stopWatch = new StopWatch();
            // 首先启动一个计时器
            stopWatch.start();
            ConfigurableApplicationContext context = null;
            // 异常报告
            Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList();
            this.configureHeadlessProperty();
            // 重点这句话
            SpringApplicationRunListeners listeners = this.getRunListeners(args);
            // 启动从jar下面的spring.factories获取到的所有监听器
            listeners.starting();
    
            Collection exceptionReporters;
            try {
                // 将咱们启动传进来的参数  封装成一个ApplicationArguments对象
                ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
                // 将listeners和参数出入  调用prepareEnvironment  来看下prepareEnvironment方法
                ConfigurableEnvironment environment = this.prepareEnvironment(listeners, applicationArguments);
                this.configureIgnoreBeanInfo(environment);
                Banner printedBanner = this.printBanner(environment);
                context = this.createApplicationContext();
                exceptionReporters = this.getSpringFactoriesInstances(SpringBootExceptionReporter.class, new Class[]{ConfigurableApplicationContext.class}, context);
                this.prepareContext(context, environment, listeners, applicationArguments, printedBanner);
                this.refreshContext(context);
                this.afterRefresh(context, applicationArguments);
                stopWatch.stop();
                if (this.logStartupInfo) {
                    (new StartupInfoLogger(this.mainApplicationClass)).logStarted(this.getApplicationLog(), stopWatch);
                }
    
                listeners.started(context);
                this.callRunners(context, applicationArguments);
            } catch (Throwable var10) {
                this.handleRunFailure(context, var10, exceptionReporters, listeners);
                throw new IllegalStateException(var10);
            }
    
            try {
                listeners.running(context);
                return context;
            } catch (Throwable var9) {
                this.handleRunFailure(context, var9, exceptionReporters, (SpringApplicationRunListeners)null);
                throw new IllegalStateException(var9);
            }
        }

SpringApplicationRunListeners listeners = this.getRunListeners(args);
    
    
    
    
    
    private SpringApplicationRunListeners getRunListeners(String[] args) {
            Class<?>[] types = new Class[]{SpringApplication.class, String[].class};
            return new SpringApplicationRunListeners(logger, this.getSpringFactoriesInstances(SpringApplicationRunListener.class, types, this, args));
        }

> 这里面调用了this.getSpringFactoriesInstances方法   在上篇中咱们有说过这个方法的作用和原理   可以去看下     就是从springFactories文件找到SpringApplicationRunListener相对应的一个个容器  并且通过反射的方法去构建一个个的容器

prepareEnvironment方法  从字面意思来看是准备环境

private ConfigurableEnvironment prepareEnvironment(SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments) {
            ConfigurableEnvironment environment = this.getOrCreateEnvironment();
            this.configureEnvironment((ConfigurableEnvironment)environment, applicationArguments.getSourceArgs());
            ConfigurationPropertySources.attach((Environment)environment);
            // 将环境装在在lister里面
            listeners.environmentPrepared((ConfigurableEnvironment)environment);
            // 并且绑定在的SpringApplication   这样的话 咱们环境就算准备好了  
            this.bindToSpringApplication((ConfigurableEnvironment)environment);
            if (!this.isCustomEnvironment) {
                environment = (new EnvironmentConverter(this.getClassLoader())).convertEnvironmentIfNecessary((ConfigurableEnvironment)environment, this.deduceEnvironmentClass());
            }
    
            ConfigurationPropertySources.attach((Environment)environment);
            return (ConfigurableEnvironment)environment;
        }

首先它调用了getOrCreateEnvironment方法   里面主要判断咱们环境是什么环境    因为我们是web项目   那么他的环境标识的话是servlet

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zNzAxMjg4MQ_size_16_color_FFFFFF_t_70][]

咱们再往下面走    Banner printedBanner = this.printBanner(environment);   这个就是打印咱们spring的标示图  可以看下

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zNzAxMjg4MQ_size_16_color_FFFFFF_t_70 1][]

context = this.createApplicationContext();  主要是创建ioc容器  会根据咱们的环境去加载相对应的ioc容器

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zNzAxMjg4MQ_size_16_color_FFFFFF_t_70 2][]

this.prepareContext(context, environment, listeners, applicationArguments, printedBanner);  将我们listeners和参数 环境都存在ioc里面

this.refreshContext(context);这里很重要  这个地方就是ioc容器  开始收集咱们的程序里面的注解 将需要加载到ioc里面的类，包都一个个加到容器里面  可以看下里面  一句话 就是刷新容器 开始注入容器

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zNzAxMjg4MQ_size_16_color_FFFFFF_t_70 3][]

到这里  run方法已经说完了   可能里面某个点说的不是特别好   欢迎纠正   有些地方可以帮到你们   打完收工

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zNzAxMjg4MQ_size_16_color_FFFFFF_t_70 4][]

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