启动入口
@SpringBootApplication
public class DemoApplication {public static void main(String[] args) {
// step.1
SpringApplication.run(DemoApplication.class, args);
}
}
实例化 SpringApplication 对象
// step.2
public static ConfigurableApplicationContext run(Class<?> primarySource, String... args) {return run(new Class[]{primarySource}, args);
}
// step.3
// 实例化 SpringApplication 对象,在构造方法内加载一些资源
public static ConfigurableApplicationContext run(Class<?>[] primarySources, String[] args) {return new SpringApplication(primarySources).run(args);
}
// step.4
public SpringApplication(Class<?>... primarySources) {this(null, primarySources);
}
加载运行类信息 & 确定利用类型 & 加载初始化器 & 加载监听器 & 设置运行主类
// step.5
@SuppressWarnings({"unchecked", "rawtypes"})
public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {
this.resourceLoader = resourceLoader;
Assert.notNull(primarySources, "PrimarySources must not be null");
// 加载运行类信息,此处的 primarySources 实际上是启动传入的 class
this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
// 确定利用类型,默认 servlet
this.webApplicationType = WebApplicationType.deduceFromClasspath();
this.bootstrapRegistryInitializers = new ArrayList<>(getSpringFactoriesInstances(BootstrapRegistryInitializer.class));
// 加载初始化器
setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
// 加载监听器
setListeners((Collection)getSpringFactoriesInstances(ApplicationListener.class));
// 设置运行主类
this.mainApplicationClass = deduceMainApplicationClass();}
如果心愿自定义初始化器,则须要实现 ApplicationContextInitializer 接口
加载心愿自定义监听器,则须要实现 ApplicationListener 接口
以上两者都须要在 resources 目录下增加 META-INF/spring.factories 配置文件,将自定义的初始化器注册进去
执行启动办法 run()
// step.6
/**
* Run the Spring application, creating and refreshing a new
* {@link ApplicationContext}.
* @param args the application arguments (usually passed from a Java main method)
* @return a running {@link ApplicationContext}
*/
public ConfigurableApplicationContext run(String... args) {
// 记录启动开始工夫
long startTime = System.nanoTime();
DefaultBootstrapContext bootstrapContext = createBootstrapContext();
// 申明利用上下文
ConfigurableApplicationContext context = null;
// 设置 无显示器仍然启动
configureHeadlessProperty();
// 创立所有 Spring 运行监听器并公布利用启动事件 并启用监听器
SpringApplicationRunListeners listeners = getRunListeners(args);
listeners.starting(bootstrapContext, this.mainApplicationClass);
try {
// 封装利用参数
ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
// 环境筹备
ConfigurableEnvironment environment = prepareEnvironment(listeners, bootstrapContext, applicationArguments);
configureIgnoreBeanInfo(environment);
// 打印 banner
Banner printedBanner = printBanner(environment);
// 创立利用上下文
context = createApplicationContext();
context.setApplicationStartup(this.applicationStartup);
// 把相干的类放入上下文中
prepareContext(bootstrapContext, context, environment, listeners, applicationArguments, printedBanner);
// 刷新上下文;// 将上述被加载的 bean 实例化;// @EnableAutoConfiguration 配置在此拆卸
// 启动 tomcat
refreshContext(context);
// 刷新上下文后置解决
afterRefresh(context, applicationArguments);
// 记录启动实现时长
Duration timeTakenToStartup = Duration.ofNanos(System.nanoTime() - startTime);
if (this.logStartupInfo) {new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), timeTakenToStartup);
}
// 公布上下文准备就绪事件
listeners.started(context, timeTakenToStartup);
// 执行自定义的 run 办法
callRunners(context, applicationArguments);
}
catch (Throwable ex) {handleRunFailure(context, ex, listeners);
throw new IllegalStateException(ex);
}
try {Duration timeTakenToReady = Duration.ofNanos(System.nanoTime() - startTime);
listeners.ready(context, timeTakenToReady);
}
catch (Throwable ex) {handleRunFailure(context, ex, null);
throw new IllegalStateException(ex);
}
return context;
}
运行时监听器
扩大性能 callRunners(context, applicationArguments)
能够在启动实现后执行自定义的内容;有 2 种实现形式
- 实现 ApplicationRunner 接口
- 实现 CommandLineRunner 接口
参考资料:
https://blog.csdn.net/weixin_…
https://blog.csdn.net/w200921…