SpringBoot 2.x 框架整体启动流程概览

分手后的思念是犯贱 2022-10-06 11:00 37阅读 0赞

### 文章目录 ###

*   *   *  启动流程
         *  完整的启动流程图

### 启动流程 ###

主要分为三步: 1.框架初始化 2. 框架启动 3. 自动化装配

*  框架初始化: `new SpringApplication(primarySources).run(args);` 调用SpringApplication的构造方法  
    构造方法中, 执行如下的代码, 进行框架的初始化
    
        public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) { 
        		// 1. 配置资源加载器
        		this.resourceLoader = resourceLoader;
        		Assert.notNull(primarySources, "PrimarySources must not be null");
        		// 2. 配置primarySources 
        		this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
        		// 3. 应用环境监测 
        		this.webApplicationType = WebApplicationType.deduceFromClasspath();
        		// 4. 配置系统初始化器 
        		setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
        		// 5. 配置应用监听器 
        		setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
        		// 6. 配置main 方法所在的类 
        		this.mainApplicationClass = deduceMainApplicationClass();
        	}
 *  框架启动: SpringApplication 初始化完成后, 调用run方法, 进行框架的启动. run方法如下
    
        public ConfigurableApplicationContext run(String... args) { 
        	  // 1. 计时器开始计时 
        		StopWatch stopWatch = new StopWatch();
        		stopWatch.start();
        		ConfigurableApplicationContext context = null;
        		Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();
        		// 2. Headless 模式赋值 : 工作在一个没有显示器键盘的环境
        		configureHeadlessProperty();
        		// 3. 发送ApplicationStartingEvent 监听事件 
        		SpringApplicationRunListeners listeners = getRunListeners(args);
        		listeners.starting();
        		try { 
        				// 4. 配置环境模块
        			ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
        	// 5. 发送 ApplicationEnvironmentPreparedEvent
        			ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);
        			configureIgnoreBeanInfo(environment);
        			// 6. 打印banner
        			Banner printedBanner = printBanner(environment);
        			// 7. 创建应用上下文对象 
        			context = createApplicationContext();
        			// 8. 初始化失败分析器 
        			exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,
        					new Class[] {  ConfigurableApplicationContext.class }, context);
        					// 9. 关联SpringBoot 组件和应用上下文对象 
        					// 10. 在prepareContext 方法中发送ApplicationContextInitializedEvent 
        			prepareContext(context, environment, listeners, applicationArguments, printedBanner);
        			// 11. 加载sources到context当中
        			 // 12. 发送ApplicationPreparedEvent 
        			 // 13. 刷新上下文
        			refreshContext(context);
        			afterRefresh(context, applicationArguments);
        			// 14. 计时器停止计时 . 
        			stopWatch.stop();
        			if (this.logStartupInfo) { 
        				new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);
        			}
        			// 15. 发送ApplicationStartedEvent事件
        			listeners.started(context);
        			// 16. 调用框架启动扩展类
        			// 17. 发送ApplicationReadyEvent 事件
        			callRunners(context, applicationArguments);
        		}
        		catch (Throwable ex) { 
        			handleRunFailure(context, ex, exceptionReporters, listeners);
        			throw new IllegalStateException(ex);
        		}
        
        		try { 
        			listeners.running(context);
        		}
        		catch (Throwable ex) { 
        			handleRunFailure(context, ex, exceptionReporters, null);
        			throw new IllegalStateException(ex);
        		}
        		return context;
        	}
 *  自动化装配:
    
    1.  收集配置文件中的配置工厂类
    2.  加载组件工厂
    3.  注册组件内定义的bean

### 完整的启动流程图 ###

完整的启动流程图如下.  
在线浏览图片  
[https://www.processon.com/view/link/60c580aa7d9c0879372476bd][https_www.processon.com_view_link_60c580aa7d9c0879372476bd]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMzMjI5NjY5_size_16_color_FFFFFF_t_70_pic_center]

[https_www.processon.com_view_link_60c580aa7d9c0879372476bd]: https://www.processon.com/view/link/60c580aa7d9c0879372476bd
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzMzMjI5NjY5_size_16_color_FFFFFF_t_70_pic_center]: /images/20221005/e04aaac73e9843f295ecd2c16d54b625.png