SpringApplication

自动以SpringApplication

SpringApplication是springboot驱动spring应用上下文的引导类

@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan(excludeFilters = {
        @Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class),
        @Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) })
public @interface SpringBootApplication {
    ...
}

@ComponentScan:扫描。它是什么版本引入的？Spring Framework3.1

@EnableAutoConfiguration ：激动自动装配@Enable->@Enable开头的

​ （1）@EnableWebMvc

​ (2)@EnableTransationManagement

​ (3)@EnableAspectJAutoProxy

​ (4)EnableAsync

@SpringBootConfiguration:等价于@Configuration->Configuration Class 注解

@Component的“派生性”

@Component

@Component -> @ComponentScan

处理类 -> ConfigurationClassParser

扫描类 ->

 

ClassPathBeanDefinitionScanner

ClassPathScanningCandidateComponentProvider

protected void registerDefaultFilters() {
    this.includeFilters.add(new AnnotationTypeFilter(Component.class));
    ...
}

Dubbo @Service -> 2.5.7 -> new AnnotationTypeFilter(Service.class);

 

Spring 注解编程模型

 

@Component

@Service

@Component
​
public @interface Service {
​
    ...
​
}

@Repository

@Component
​
public @interface Repository {
​
    ...
​
}

@Controller

@Component
​
public @interface Controller {
​
    ...
​
}

@Configuration

@Component
​
public @interface Configuration {
​
    ...
​
}

Spring 模式注解：Stereotype Annotations

Spring 注解驱动示例

注解驱动上下文 AnnotationConfigApplicationContext ， Spring Framework 3.0 开始引入的

@Configurationpublic class SpringAnnotationDemo {

public static void main(String[] args) {
​
    //   XML 配置文件驱动       ClassPathXmlApplicationContext
    // Annotation 驱动
    // 找 BeanDefinition
    // @Bean @Configuration
    AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
    // 注册一个 Configuration Class = SpringAnnotationDemo
    context.register(SpringAnnotationDemo.class);
    // 上下文启动
    context.refresh();
​
    System.out.println(context.getBean(SpringAnnotationDemo.class));
​
}

}@SpringBootApplication 标注当前一些功能

 

@SpringBootApplication

@SpringBootConfiguration

@Configuration

@Component

 

 

SpringApplication Spring Boot 应用的引导

基本写法

SpringApplication springApplication = new SpringApplication(MicroservicesProjectApplication.class); Map<String,Object> properties = new LinkedHashMap<>(); properties.put("server.port",0); springApplication.setDefaultProperties(properties); springApplication.run(args);

SpringApplicationBuilder

    new SpringApplicationBuilder(MicroservicesProjectApplication.class) // Fluent API
            // 单元测试是 PORT = RANDOM
            .properties("server.port=0")  // 随机向 OS 要可用端口
            .run(args);

Spring Boot 引导示例

@SpringBootApplicationpublic class MicroservicesProjectApplication {

public static void main(String[] args) {
    SpringApplication springApplication = new SpringApplication(MicroservicesProjectApplication.class);
    Map<String,Object> properties = new LinkedHashMap<>();
    properties.put("server.port",0);
    springApplication.setDefaultProperties(properties);
    ConfigurableApplicationContext context = springApplication.run(args);
    // 有异常？
    System.out.println(context.getBean(MicroservicesProjectApplication.class));
}

}

调整示例为 非 Web 程序

@SpringBootApplicationpublic class MicroservicesProjectApplication {

public static void main(String[] args) {
    SpringApplication springApplication = new SpringApplication(MicroservicesProjectApplication.class);
    Map<String, Object> properties = new LinkedHashMap<>();
    properties.put("server.port", 0);
    springApplication.setDefaultProperties(properties);
    // 设置为 非 web 应用
    springApplication.setWebApplicationType(WebApplicationType.NONE);
    ConfigurableApplicationContext context = springApplication.run(args);
    // 有异常？
    System.out.println(context.getBean(MicroservicesProjectApplication.class));
    // 输出当前 Spring Boot 应用的 ApplicationContext 的类名
    System.out.println("当前 Spring 应用上下文的类：" + context.getClass().getName());
}

}输出结果：

当前 Spring 应用上下文的类：org.springframework.context.annotation.AnnotationConfigApplicationContext

配置 Spring Boot 源

SpringAppliation 类型推断

当不加以设置 Web 类型，那么它采用推断：

-> SpringAppliation() -> deduceWebApplicationType() 第一次推断为 WebApplicationType.SERVLET

 

WebApplicationType.NONE : 非 Web 类型

 

Servlet 不存在Spring Web 应用上下文 ConfigurableWebApplicationContext 不存在

spring-boot-starter-web 不存在

spring-boot-starter-webflux 不存在

 

WebApplicationType.REACTIVE : Spring WebFlux

DispatcherHandler

spring-boot-starter-webflux 存在

Servlet 不存在

spring-boot-starter-web 不存在

 

WebApplicationType.SERVLET : Spring MVC

 

spring-boot-starter-web 存在

 

 

人工干预 Web 类型

设置 webApplicationType 属性 为 WebApplicationType.NONE

Spring Boot 事件

Spring 事件

Spring 内部发送事件

 

ContextRefreshedEvent

ApplicationContextEventApplicationEvent

 

refresh() -> finishRefresh() -> publishEvent(new ContextRefreshedEvent(this));

 

ContextClosedEvent

ApplicationContextEventApplicationEvent

 

close() -> doClose() -> publishEvent(new ContextClosedEvent(this));

自定义事件

PayloadApplicationEvent

Spring 事件 都是 ApplicationEvent 类型

发送 Spring 事件通过 ApplicationEventMulticaster#multicastEvent(ApplicationEvent, ResolvableType)

Spring 事件的类型 ApplicationEvent

Spring 事件监听器 ApplicationListener

Spring 事件广播器 ApplicationEventMulticaster

实现类：SimpleApplicationEventMulticaster

 

Spring 事件理解为消息

ApplicationEvent 相当于消息内容

ApplicationListener 相当于消息消费者、订阅者

ApplicationEventMulticaster 相当于消息生产者、发布者

Spring Boot 事件监听示例

@EnableAutoConfigurationpublic class SpringBootEventDemo {

public static void main(String[] args) {
    new SpringApplicationBuilder(SpringBootEventDemo.class)
            .listeners(event -> { // 增加监听器
                System.err.println("监听到事件 ： " + event.getClass().getSimpleName());
            })
            .run(args)
            .close();
    ; // 运行
}

}

ApplicationStartingEvent（1）ApplicationEnvironmentPreparedEvent（2）ApplicationPreparedEvent（3）ContextRefreshedEventServletWebServerInitializedEventApplicationStartedEvent（4）ApplicationReadyEvent（5）ContextClosedEventApplicationFailedEvent (特殊情况)（6）

Spring Boot 事件监听器

org.springframework.context.ApplicationListener=\
org.springframework.boot.ClearCachesApplicationListener,\
org.springframework.boot.builder.ParentContextCloserApplicationListener,\
org.springframework.boot.context.FileEncodingApplicationListener,\
org.springframework.boot.context.config.AnsiOutputApplicationListener,\
org.springframework.boot.context.config.ConfigFileApplicationListener,\
org.springframework.boot.context.config.DelegatingApplicationListener,\
org.springframework.boot.context.logging.ClasspathLoggingApplicationListener,\
org.springframework.boot.context.logging.LoggingApplicationListener,\
org.springframework.boot.liquibase.LiquibaseServiceLocatorApplicationListener
ConfigFileApplicationListener 监听 ApplicationEnvironmentPreparedEvent 事件

从而加载 application.properties 或者 application.yml 文件

Spring Boot 很多组件依赖于 Spring Boot 事件监听器实现，本质是 Spring Framework 事件/监听机制

SpringApplication 利用

Spring 应用上下文（ApplicationContext）生命周期控制 注解驱动 Bean Spring 事件/监听（ApplicationEventMulticaster）机制加载或者初始化组件