SpringApplication构造分析
1、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。
2、推断应用类型
根据jar包去判断是什么引用类型
3、记录 ApplicationContext 初始化器
对ApplicationContext做扩展
4、记录监听器
监听重要事件
5、推断主启动类
记录运行的主类。
SpringApplication run分析
1、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
}
2、封装启动 args
3、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"));
}
4、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"));
}
}
5、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());
/*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);
}
}
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"));
}
}
6、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);
}
7、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);
}
}
8、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;
}
9、准备容器发布
application context 已初始化事件
10、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");
11、refresh 容器
发布 application started 事件
12、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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原文出处：https://blog.csdn.net/PnJgHT/article/details/125674291