spring 36 Boot 启动过程
阶段一：SpringApplication 构造
点击查看代码
构造源码：
public SpringApplication(Class<?>... primarySources) {
this(null, primarySources);
}
public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {
this.resourceLoader = resourceLoader;
Assert.notNull(primarySources, "PrimarySources must not be null");
this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
this.webApplicationType = WebApplicationType.deduceFromClasspath();
this.bootstrapRegistryInitializers = getBootstrapRegistryInitializersFromSpringFactories();
setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
this.mainApplicationClass = deduceMainApplicationClass();
}
演示：
public static void main(String[] args) throws Exception {
System.out.println("1. 演示获取 Bean Definition 源");
SpringApplication spring = new SpringApplication(A39_1.class);
spring.setSources(Set.of("classpath:b01.xml"));
System.out.println("2. 演示推断应用类型");
Method deduceFromClasspath = WebApplicationType.class.getDeclaredMethod("deduceFromClasspath");
deduceFromClasspath.setAccessible(true);
System.out.println("\t应用类型为:"+deduceFromClasspath.invoke(null));
System.out.println("3. 演示 ApplicationContext 初始化器");
spring.addInitializers(applicationContext -> {
if (applicationContext instanceof GenericApplicationContext gac) {
gac.registerBean("bean3", Bean3.class);
}
});
System.out.println("4. 演示监听器与事件");
spring.addListeners(event -> System.out.println("\t事件为:" + event.getClass()));
System.out.println("5. 演示主类推断");
Method deduceMainApplicationClass = SpringApplication.class.getDeclaredMethod("deduceMainApplicationClass");
deduceMainApplicationClass.setAccessible(true);
System.out.println("\t主类是："+deduceMainApplicationClass.invoke(spring));
ConfigurableApplicationContext context = spring.run(args);
// 创建 ApplicationContext
// 调用初始化器 对 ApplicationContext 做扩展
// ApplicationContext.refresh
for (String name : context.getBeanDefinitionNames()) {
System.out.println("name: " + name + " 来源：" + context.getBeanFactory().getBeanDefinition(name).getResourceDescription());
}
context.close();
- 记录 BeanDefinition 源
- 推断应用类型
- 记录 ApplicationContext 初始化器
- 记录监听器
- 推断主启动类
阶段二：执行 run 方法
- 得到 SpringApplicationRunListeners，名字取得不好，实际是事件发布器
点击查看代码
// 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(); //初始化 spring 容器
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
}
- 发布 application starting 事件1️⃣
- 封装启动 args
点击查看代码
SpringApplication app = new SpringApplication();
app.addInitializers(new ApplicationContextInitializer<ConfigurableApplicationContext>() {
@Override
public void initialize(ConfigurableApplicationContext applicationContext) {
System.out.println("执行初始化器增强...");
}
}); // 添加初始化器
System.out.println(">>>>>>>>>>>>>>>>>>>>>>>> 2. 封装启动 args");
DefaultApplicationArguments arguments = new DefaultApplicationArguments(args); //供 ApplicationRunner 使用
System.out.println(">>>>>>>>>>>>>>>>>>>>>>>> 8. 创建容器");
GenericApplicationContext context = createApplicationContext(WebApplicationType.SERVLET);
System.out.println(">>>>>>>>>>>>>>>>>>>>>>>> 9. 准备容器");
for (ApplicationContextInitializer initializer : app.getInitializers()) {
initializer.initialize(context); //回调初始化器，扩展 spring 容器
}
System.out.println(">>>>>>>>>>>>>>>>>>>>>>>> 10. 加载 bean 定义");
DefaultListableBeanFactory beanFactory = context.getDefaultListableBeanFactory();
AnnotatedBeanDefinitionReader reader1 = new AnnotatedBeanDefinitionReader(beanFactory);
XmlBeanDefinitionReader reader2 = new XmlBeanDefinitionReader(beanFactory);
ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(beanFactory);
reader1.register(Config.class); //配置类
reader2.loadBeanDefinitions(new ClassPathResource("b03.xml")); //xml 文件
scanner.scan("com.itheima.a39.sub"); //包扫描
System.out.println(">>>>>>>>>>>>>>>>>>>>>>>> 11. refresh 容器");
context.refresh();
for (String name : context.getBeanDefinitionNames()) {
System.out.println("name:" + name + " 来源：" + beanFactory.getBeanDefinition(name).getResourceDescription());
}
System.out.println(">>>>>>>>>>>>>>>>>>>>>>>> 12. 执行 runner");
for (CommandLineRunner runner : context.getBeansOfType(CommandLineRunner.class).values()) {
runner.run(args);
}
for (ApplicationRunner runner : context.getBeansOfType(ApplicationRunner.class).values()) {
runner.run(arguments);
}
- 准备 Environment 添加命令行参数（*）
点击查看代码
ApplicationEnvironment env = new ApplicationEnvironment(); //优先级： 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（*）
点击查看代码
ApplicationEnvironment env = new ApplicationEnvironment();
env.getPropertySources().addLast(
new ResourcePropertySource("step4", new ClassPathResource("step4.properties"))
);
ConfigurationPropertySources.attach(env); //添加一个源到最顶层，使驼峰命名，下划线命名，杠命名都能被识别。
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"));
- 发布 application environment 已准备事件2️⃣
- 通过 EnvironmentPostProcessorApplicationListener 进行 env 后处理（*）
点击查看代码
SpringApplication app = new SpringApplication();
ApplicationEnvironment env = new ApplicationEnvironment();
System.out.println(">>>>>>>>>>>>>>>>>>>>>>>>> 增强前");
for (PropertySource<?> ps : env.getPropertySources()) {
System.out.println(ps);
}
//将 application.properties 加入其中
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);
}
//获得随机数据的源
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")); //获得随机的 int 值
System.out.println(env.getProperty("random.int"));
System.out.println(env.getProperty("random.int"));
System.out.println(env.getProperty("random.uuid")); //获得随机的 uuid
System.out.println(env.getProperty("random.uuid"));
System.out.println(env.getProperty("random.uuid"));
/*
可以添加参数 --spring.application.json={\"server\":{\"port\":9090}} 测试 SpringApplicationJsonEnvironmentPostProcessor
*/
SpringApplication app = new SpringApplication();
//spring boot 从 spring.factory 中找到对应的源，不写死，
app.addListeners(new EnvironmentPostProcessorApplicationListener());
List<String> names = SpringFactoriesLoader.loadFactoryNames(EnvironmentPostProcessor.class, Step5.class.getClassLoader());
for (String name : names) {
System.out.println(name);
}
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);
}
- application.properties，由 StandardConfigDataLocationResolver 解析
- spring.application.json
- 绑定 spring.main 到 SpringApplication 对象（*）
点击查看代码
// 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("step4", new ClassPathResource("step4.properties")));
env.getPropertySources().addLast(new ResourcePropertySource("step6", new ClassPathResource("step6.properties")));
// User user = Binder.get(env).bind("user", User.class).get();
// System.out.println(user);
// User user = new User();
// Binder.get(env).bind("user", Bindable.ofInstance(user));
// System.out.println(user);
System.out.println(application);
Binder.get(env).bind("spring.main", Bindable.ofInstance(application));
System.out.println(application);
}
- 打印 banner（*）
点击查看代码
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
-
准备容器
- 发布 application context 已初始化事件3️⃣
-
加载 bean 定义
- 发布 application prepared 事件4️⃣
-
refresh 容器
- 发布 application started 事件5️⃣
-
执行 runner
-
发布 application ready 事件6️⃣
-
这其中有异常，发布 application failed 事件7️⃣
-
小结：
- SpringApplication 构造方法中所做的操作
- 可以有多种源用来加载 bean 定义
- 应用类型推断
- 添加容器初始化器
- 添加监听器
- 演示主类推断
- 如何读取 spring.factories 中的配置
- 从配置中获取重要的事件发布器：SpringApplicationRunListeners
- 容器的创建、初始化器增强、加载 bean 定义等
- CommandLineRunner、ApplicationRunner 的作用
- 环境对象
- 命令行 PropertySource
- ConfigurationPropertySources 规范环境键名称
- EnvironmentPostProcessor 后处理增强
- 由 EventPublishingRunListener 通过监听事件2️⃣来调用
- 绑定 spring.main 前缀的 key value 至 SpringApplication
- Banner
