springboot启动解析三

此篇文章继续解析SpringApplication的run方法具体代码如下：

public ConfigurableApplicationContext run(String... args) {
        1.StopWatch stopWatch = new StopWatch();
        2.stopWatch.start();
        3.ConfigurableApplicationContext context = null;
        4.Collection exceptionReporters = new ArrayList<>();
        5.configureHeadlessProperty();
        6.SpringApplicationRunListeners listeners = getRunListeners(args);
        7.listeners.starting();
        try {
        8.  ApplicationArguments applicationArguments = new DefaultApplicationArguments(
                    args);
        9.  ConfigurableEnvironment environment = prepareEnvironment(listeners,
                    applicationArguments);
        10. configureIgnoreBeanInfo(environment);
        11. Banner printedBanner = printBanner(environment);
        12. context = createApplicationContext();
        13. exceptionReporters = getSpringFactoriesInstances(
                SpringBootExceptionReporter.class,
                    new Class[] { ConfigurableApplicationContext.class }, context);
        14.     prepareContext(context, environment, listeners, applicationArguments,
                    printedBanner);
        15. refreshContext(context);
        16. afterRefresh(context, applicationArguments);
        17. stopWatch.stop();
        18. if (this.logStartupInfo) {
        19.     new StartupInfoLogger(this.mainApplicationClass)
                        .logStarted(getApplicationLog(), stopWatch);
            }
        20. listeners.started(context);
        21. callRunners(context, applicationArguments);
        }
        catch (Throwable ex) {
        22. handleRunFailure(context, ex, exceptionReporters, listeners);
            throw new IllegalStateException(ex);
        }

        try {
        23. listeners.running(context);
        }
        catch (Throwable ex) {
        24. handleRunFailure(context, ex, exceptionReporters, null);
            throw new IllegalStateException(ex);
        }
        return context;
    }

一共24行代码，本章主要解析8-11小节。

ApplicationArguments

• 当我们把springboot 打包成jar包运行的时候输入jar -jar test.jar --debug test.log，则我们通过ApplicationArguments 获取到的参数就是"--debug test.log"，而ApplicationArguments 可以将这些参数转化成key和value形式

ConfigurableEnvironment

这边创建我们的运行时候环境

    private ConfigurableEnvironment getOrCreateEnvironment() {
    如果我们自己设置了environment，则直接使用
        if (this.environment != null) {
            return this.environment;
        }
否则根据webApplicationType 选择合适的webApplicationType 
        if (this.webApplicationType == WebApplicationType.SERVLET) {
            return new StandardServletEnvironment();
        }
        return new StandardEnvironment();
    }

根据@Profile和spring.profiles.active=xxx 可以在不同的情况下初始化不同的类，但是我们一般都采用这种方式来隔离线上和线下环境

    protected void configureEnvironment(ConfigurableEnvironment environment,
            String[] args) {
将参数和一些默认的属性配置到environment
        configurePropertySources(environment, args);
激活profile
        configureProfiles(environment, args);
    }

调用SpringApplicationRunListener的environmentPrepared方法,我们在这里面更新了我environent的配置PropertySource,可以看到我们在这里吗通过监听其设置我们的一些propertysource的具体文位置，或者设置具体的对象（主要是通过ConfigFileApplicationListener）

比如StandardServletEnvironment {activeProfiles=[], defaultProfiles=[default],

• 1. propertySources=[StubPropertySource {name='servletConfigInitParams'}, StubPropertySource

• 2.{name='servletContextInitParams'}, MapPropertySource {name='systemProperties'},

-3.OriginAwareSystemEnvironmentPropertySource {name='systemEnvironment'},

• 4.RandomValuePropertySource {name='random'},

• 5. OriginTrackedMapPropertySource {name='applicationConfig: [classpath:/application.properties]'}]}

    public void environmentPrepared(ConfigurableEnvironment environment) {
        for (SpringApplicationRunListener listener : this.listeners) {
            listener.environmentPrepared(environment);
        }
    }

就是把SpringApplication和"spring.main"绑定放入environment对应的Binder

    protected void bindToSpringApplication(ConfigurableEnvironment environment) {
        try {
            Binder.get(environment).bind("spring.main", Bindable.ofInstance(this));
        }
        catch (Exception ex) {
            throw new IllegalStateException("Cannot bind to SpringApplication", ex);
        }
    }

如果webApplicationType是为none 则创建一个EnvironmentConverter 并且转化成StandardEnvironment

    if (this.webApplicationType == WebApplicationType.NONE) {
            environment = new EnvironmentConverter(getClassLoader())
                    .convertToStandardEnvironmentIfNecessary(environment);
        }
        ConfigurationPropertySources.attach(environment);

从environment获取MutablePropertySources ，然后删除若已经存在的属性configurationProperties，然后创建一个ConfigurationPropertySourcesPropertySource，其内部把属性configurationProperties设置为对应的SpringConfigurationPropertySources

• 这边的两个类还不清楚专门干嘛的SpringConfigurationPropertySources和ConfigurationPropertySourcesPropertySource

public static void attach(Environment environment) {
        Assert.isInstanceOf(ConfigurableEnvironment.class, environment);
        MutablePropertySources sources = ((ConfigurableEnvironment) environment)
                .getPropertySources();
        PropertySource attached = sources.get(ATTACHED_PROPERTY_SOURCE_NAME);
        if (attached != null && attached.getSource() != sources) {
            sources.remove(ATTACHED_PROPERTY_SOURCE_NAME);
            attached = null;
        }
        if (attached == null) {
            sources.addFirst(new ConfigurationPropertySourcesPropertySource(
                    ATTACHED_PROPERTY_SOURCE_NAME,
                    new SpringConfigurationPropertySources(sources)));
        }
    }

设置spring.beaninfo.ignore的属性，以及打印Banner

    configureIgnoreBeanInfo(environment);
            Banner printedBanner = printBanner(environment);

• PropertySources：一个接口提供了对PropertySource的迭代操作
• PropertySource：是一个容器里面存储了各个source（每个source有一个对应的名字）
• ConfigurationPropertySourcesPropertySource继承了PropertySource且实现了OriginLookup（可以寻找）
  其中ConfigurationPropertySourcesPropertySource的source是ConfigurationPropertySource
  我们在这边塞入的SpringConfigurationPropertySources就是其一个子类

总结：本篇文章主要介绍了ConfigurableEnvironment的创建以及设置其PropertySource