Springboot  的一些基础源码分析 （一）SpringApplication执行流程

参考：https://www.cnblogs.com/red-code/p/9267106.html

@SpringBootApplication(exclude = {DataSourceAutoConfiguration.class})
public class JustfottestApplication {

    public static void main(String[] args) {
        SpringApplication.run(JustfottestApplication.class, args);
    }

}

SpringApplication.run(JustfottestApplication.class, args);  其中第一个参数是入口类 第二个参数是启动Spring应用的命令行参数，该参数可以在Spring应用中被访问。 

其中 SpringApplication.run 跳 了几个run之后调用

 真正的run 

public ConfigurableApplicationContext run(String... args) {
        StopWatch stopWatch = new StopWatch();
        stopWatch.start();
        ConfigurableApplicationContext context = null;
        Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList();
        this.configureHeadlessProperty();
        SpringApplicationRunListeners listeners = this.getRunListeners(args);
        listeners.starting();

        Collection exceptionReporters;
        try {
            ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
            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);
        }
    }

run 方法解析

•  public ConfigurableApplicationContext run(String... args) {
  //stopwatch是记录时间的，不管他
          StopWatch stopWatch = new StopWatch();
          stopWatch.start();
          ConfigurableApplicationContext context = null;
          Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList();
          this.configureHeadlessProperty();
  // 启动listen 之后详细说
          SpringApplicationRunListeners listeners = this.getRunListeners(args);
          listeners.starting();

          Collection exceptionReporters;
          try {
  //获取前面说的命令行参数
              ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
  //获取 environment  并通知listener
              ConfigurableEnvironment environment = this.prepareEnvironment(listeners, applicationArguments);
  //是否用banner
              this.configureIgnoreBeanInfo(environment);
  //设置banner   
              Banner printedBanner = this.printBanner(environment);
  /*调用了 protected ConfigurableApplicationContext createApplicationContext()
  *这个方法中是根据不同的webApplicationType  返回不同的实例 applicationContextClass

  *而  webApplicationType 是在初始化的时候 this.webApplicationType = *WebApplicationType.deduceFromClasspath();  确定是哪种类型的 
  *
  none （不在web容器的普通工程） servlet（servlet） reactive(响应式)的 
  *
  */

• 得到相应的应用上下文
              context = this.createApplicationContext();
  //getSpringFactoriesInstances会调用SpringFactoriesLoader.loadFactoryNames方法，这个方法的目的是从“META-INF/spring.factories文件中加载配置
  可实际上我们一般在开发springboot项目时并没有创建过spring.factories文件，可还是自动加载了各种配置，原因如下：

  在项目的main方法上一般都会设置@SpringBootApplication注解，@SpringBootApplication注解中包含了多个注解，其中有一个@EnableAutoConfiguration注解尤为重要。

  通过@EnableAutoConfiguration注解会将org.springframework.boot.autoconfigure.EnableAutoConfiguration这个包作为查找META-INF/spring.factories文件的根目录，即spring.factories文件会从org.springframework.boot.autoconfigure.EnableAutoConfiguration包中查找。而这个包里面自然有已经写好的spring.factories文件了。

  整个springboot中会看到很多@Enable开头的注解，所有的@Enable开头的注解的作用都是通过@Import将“特定的bean”加载到Ioc容器中。@EnableAutoConfiguration的作用就是通过SpringFactoriesLoader将所有的标注了@Configuration注解的类加载（既有boot.autoconfigure包自带的标注了@Configuration的类，也可以是自己创建的标注了@Configration的类，都会被作为配置加载）
  */

• exceptionReporters 是 异常处理回调用的 SpringFactoriesLoader加载，必须包含ConfigurableApplicationContext的构造函

•             exceptionReporters = this.getSpringFactoriesInstances(SpringBootExceptionReporter.class, new Class[]{ConfigurableApplicationContext.class}, context);

• 根据上下文，环境，listener,命令行参数，banner 

• 这里源码有点多 就是把这些参数应用到一起
  并且 判断source是否为空
  然后thisload(context,sources.toArray(Object[0]))
  listeners.contextLoad(context);

• private void prepareContext(ConfigurableApplicationContext context, ConfigurableEnvironment environment, SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments, Banner printedBanner) {
      context.setEnvironment(environment);
  //生成beanNameGenerator 和 resourceLoade 和 context.getBeanFactory().setConversionService
  
      this.postProcessApplicationContext(context);
  
      this.applyInitializers(context);
      listeners.contextPrepared(context);
      if (this.logStartupInfo) {
          this.logStartupInfo(context.getParent() == null);
          this.logStartupProfileInfo(context);
      }
  
      ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
      beanFactory.registerSingleton("springApplicationArguments", applicationArguments);
      if (printedBanner != null) {
          beanFactory.registerSingleton("springBootBanner", printedBanner);
      }
  
      if (beanFactory instanceof DefaultListableBeanFactory) {
          ((DefaultListableBeanFactory)beanFactory).setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
      }
  
      Set<Object> sources = this.getAllSources();
      Assert.notEmpty(sources, "Sources must not be empty");
      this.load(context, sources.toArray(new Object[0]));
      listeners.contextLoaded(context);
  }

•             this.prepareContext(context, environment, listeners, applicationArguments, printedBanner);

• 刷新两次就好了   至于刷新的作用-----明天再说  留坑
              this.refreshContext(context);
              this.afterRefresh(context, applicationArguments);

• 停止计时
              stopWatch.stop();

• 接下来重要的就是listener.start   和  listener.running
              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);
          }
      }

•  

当然在这之前有构造方法

 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.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();
    }