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SpringApplication构造分析
记录 BeanDefinition 源
spring容器刚开始是空的，要去各个源找到beanDefinition，这些源可能是配置类，可能是xml文件。在构造方法里会获取一个主源，也就是引导类，根据引导类去获取beanDefinition。
推断应用类型
根据jar包去判断是什么引用类型
记录 ApplicationContext 初始化器
对ApplicationContext做扩展
记录监听器
监听重要事件
推断主启动类
记录运行的主类。
SpringApplication run分析
得到 SpringApplicationRunListeners，名字取得不好，实际是事件发布器
发布 application starting 事件，在程序启动的重要节点发布事件
public static void main(String[] args) throws Exception{ // 添加 app 监听器 SpringApplication app = new SpringApplication(); app.addListeners(e -> System.out.println(e.getClass())); // 获取事件发送器实现类名 List<String> names = SpringFactoriesLoader.loadFactoryNames(SpringApplicationRunListener.class, A39_2.class.getClassLoader()); for (String name : names) { System.out.println(name); Class<?> clazz = Class.forName(name); Constructor<?> constructor = clazz.getConstructor(SpringApplication.class, String[].class); SpringApplicationRunListener publisher = (SpringApplicationRunListener) constructor.newInstance(app, args); // 发布事件 DefaultBootstrapContext bootstrapContext = new DefaultBootstrapContext(); publisher.starting(bootstrapContext); // spring boot 开始启动 publisher.environmentPrepared(bootstrapContext, new StandardEnvironment()); // 环境信息准备完毕 GenericApplicationContext context = new GenericApplicationContext(); publisher.contextPrepared(context); // 在 spring 容器创建，并调用初始化器之后，发送此事件 publisher.contextLoaded(context); // 所有 bean definition 加载完毕 context.refresh(); publisher.started(context); // spring 容器初始化完成(refresh 方法调用完毕) publisher.running(context); // spring boot 启动完毕 publisher.failed(context, new Exception("出错了")); // spring boot 启动出错 }封装启动 args
准备 Environment 添加命令行参数（*）
public static void main(String[] args) throws IOException { ApplicationEnvironment env = new ApplicationEnvironment(); // 系统环境变量, properties, yaml env.getPropertySources().addLast(new ResourcePropertySource(new ClassPathResource("step3.properties"))); env.getPropertySources().addFirst(new SimpleCommandLinePropertySource(args)); for (PropertySource<?> ps : env.getPropertySources()) { System.out.println(ps); }// System.out.println(env.getProperty("JAVA_HOME")); System.out.println(env.getProperty("server.port")); }ConfigurationPropertySources 处理（*）
发布 application environment 已准备事件
public static void main(String[] args) throws IOException, NoSuchFieldException { ApplicationEnvironment env = new ApplicationEnvironment(); env.getPropertySources().addLast( new ResourcePropertySource("step4", new ClassPathResource("step4.properties")) ); ConfigurationPropertySources.attach(env); for (PropertySource<?> ps : env.getPropertySources()) { System.out.println(ps); } System.out.println(env.getProperty("user.first-name")); System.out.println(env.getProperty("user.middle-name")); System.out.println(env.getProperty("user.last-name")); }}通过 EnvironmentPostProcessorApplicationListener 进行 env 后处理（*）
application.properties，由 StandardConfigDataLocationResolver 解析
spring.application.json
public class Step5 { public static void main(String[] args) { SpringApplication app = new SpringApplication(); app.addListeners(new EnvironmentPostProcessorApplicationListener()); EventPublishingRunListener publisher = new EventPublishingRunListener(app, args); ApplicationEnvironment env = new ApplicationEnvironment(); System.out.println(">>>>>>>>>>>>>>>>>>>>>>>>> 增强前"); for (PropertySource<?> ps : env.getPropertySources()) { System.out.println(ps); } publisher.environmentPrepared(new DefaultBootstrapContext(), env); System.out.println(">>>>>>>>>>>>>>>>>>>>>>>>> 增强后"); for (PropertySource<?> ps : env.getPropertySources()) { System.out.println(ps); } } private static void test1() { SpringApplication app = new SpringApplication(); ApplicationEnvironment env = new ApplicationEnvironment(); System.out.println(">>>>>>>>>>>>>>>>>>>>>>>>> 增强前"); for (PropertySource<?> ps : env.getPropertySources()) { System.out.println(ps); } ConfigDataEnvironmentPostProcessor postProcessor1 = new ConfigDataEnvironmentPostProcessor(new DeferredLogs(), new DefaultBootstrapContext()); postProcessor1.postProcessEnvironment(env, app); System.out.println(">>>>>>>>>>>>>>>>>>>>>>>>> 增强后"); for (PropertySource<?> ps : env.getPropertySources()) { System.out.println(ps); } RandomValuePropertySourceEnvironmentPostProcessor postProcessor2 = new RandomValuePropertySourceEnvironmentPostProcessor(new DeferredLog()); postProcessor2.postProcessEnvironment(env, app); System.out.println(">>>>>>>>>>>>>>>>>>>>>>>>> 增强后"); for (PropertySource<?> ps : env.getPropertySources()) { System.out.println(ps); } System.out.println(env.getProperty("server.port")); System.out.println(env.getProperty("random.int")); System.out.println(env.getProperty("random.int")); System.out.println(env.getProperty("random.int")); System.out.println(env.getProperty("random.uuid")); System.out.println(env.getProperty("random.uuid")); System.out.println(env.getProperty("random.uuid")); }}绑定 spring.main 到 SpringApplication 对象（*）
把配置文件中的值赋给SpringApplication的默认属性值
public class Step6 { // 绑定 spring.main 前缀的 key value 至 SpringApplication, 请通过 debug 查看 public static void main(String[] args) throws IOException { SpringApplication application = new SpringApplication(); ApplicationEnvironment env = new ApplicationEnvironment(); env.getPropertySources().addLast(new ResourcePropertySource("step6", new ClassPathResource("step6.properties"))); System.out.println(application); Binder.get(env).bind("spring.main", Bindable.ofInstance(application)); System.out.println(application); }打印 banner（*）
public class Step7 { public static void main(String[] args) { ApplicationEnvironment env = new ApplicationEnvironment(); SpringApplicationBannerPrinter printer = new SpringApplicationBannerPrinter( new DefaultResourceLoader(), new SpringBootBanner() ); // 测试文字 banner// env.getPropertySources().addLast(new MapPropertySource("custom", Map.of("spring.banner.location","banner1.txt"))); // 测试图片 banner// env.getPropertySources().addLast(new MapPropertySource("custom", Map.of("spring.banner.image.location","banner2.png"))); // 版本号的获取 System.out.println(SpringBootVersion.getVersion()); printer.print(env, Step7.class, System.out); }}创建容器
private static GenericApplicationContext createApplicationContext(WebApplicationType type) { GenericApplicationContext context = null; switch (type) { case SERVLET -> context = new AnnotationConfigServletWebServerApplicationContext(); case REACTIVE -> context = new AnnotationConfigReactiveWebServerApplicationContext(); case NONE -> context = new AnnotationConfigApplicationContext(); } return context; }准备容器发布
application context 已初始化事件
加载 bean 定义
发布 application prepared 事件
DefaultListableBeanFactory beanFactory = context.getDefaultListableBeanFactory(); AnnotatedBeanDefinitionReader reader1 = new AnnotatedBeanDefinitionReader(beanFactory); XmlBeanDefinitionReader reader2 = new XmlBeanDefinitionReader(beanFactory); ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(beanFactory); reader1.register(Config.class); reader2.loadBeanDefinitions(new ClassPathResource("b03.xml")); scanner.scan("com.itheima.a39.sub");refresh 容器
发布 application started 事件
执行 runner
发布 application ready 事件
这其中有异常，发布 application failed 事件
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