没长正的技术专栏 勤动手、多思考

SpringBoot系列-SpringApplication(2)

2018-06-01

阅读:


SpringApplication

介绍SpringApplication启动,用Spring实现类似的功能。

自定义 SpringApplication (Spring)

​ 介绍 SpringApplication SpringApplicationBuilder API 调整

The SpringApplication class provides a convenient way to bootstrap a Spring application that is started from a main() method. In many situations, you can delegate to the static SpringApplication.run method

来源 SpringApplication 提供了简便的方式来启动Spring 应用。 SpringBootApplication源码:

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

其中@SpringBootConfiguration(作为配置项SpringBoot注解)源码:

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Configuration
public @interface SpringBootConfiguration {
}

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@AutoConfigurationPackage   //自动配置包
@Import({EnableAutoConfigurationImportSelector.class})
public @interface EnableAutoConfiguration { // 激活自动装配 `@Enable` -> `@Enable` 开头的
	...
}

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE})
@Documented
@Repeatable(ComponentScans.class)//允许重复包
public @interface ComponentScan {  // ----> Spring Framework 3.1 (IDEA 快捷键可查看)
	...
}

--> ComponentScans
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE})
@Documented
public @interface ComponentScans {
    ComponentScan[] value(); 
}

相当于@SpringBootApplication 等价于@ComponentScan+@EnableAutoConfiguration+@Configuration

@ComponentScan:扫描指定路径下的包

@EnableAutoConfiguration:应用所声明的依赖对Spring框架自动配置。如:

添加spring-boot-starter-web就添加了TomcatSpringMVC的依赖,类似于子项目自动添加父项目的依赖。

@Component 的“派生性”

@Component is a generic stereotype for any Spring-managed component. Any component annotated with @Component is a candidate for component scanning. Similarly, any component annotated with an annotation that is itself meta-annotated with @Component is also a candidate for component scanning. For example, @Service is meta-annotated with @Component.

Core Spring provides several stereotype annotations out of the box, including but not limited to: @Component, @Service, @Repository, @Controller, @RestController, and @Configuration. @Repository, @Service, etc. are specializations of @Component.

@Component -> @ComponentScan 阅读源码

处理类 -> ConfigurationClassParser

扫描类 ->

  • ClassPathBeanDefinitionScanner

    • ClassPathScanningCandidateComponentProvider

      	protected void registerDefaultFilters() {
      		this.includeFilters.add(new AnnotationTypeFilter(Component.class));
          	...
      	}
      
Spring 注解驱动示例(自定义实现)

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

@Configuration
public 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));

    }
}
SprigBoot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

  • SpringBoot 与Spring 关联性 (如:获取应用上下文 Context等)
@SpringBootApplication
public class MicroservicesProjectApplication {
    public static void main(String[] args) {
        SpringApplication springApplication = new SpringApplication(MicroservicesProjectApplication.class);
        //配置系统参数信息
        Map<String,Object> properties = new LinkedHashMap<>();
        properties.put("server.port",0);//随机端口
        springApplication.setDefaultProperties(properties);
        //设置为非WEB应用
        springApplication.setWebApplicationType(WebApplicationType.NONE);

        //配置类
        ConfigurableApplicationContext context = springApplication.run(args);

        //是否有异常? --> 是否已初始化
        System.out.println(context.getBean(MicroservicesProjectApplication.class));

        //输出SpringBoot 应用的Application的类名
        System.out.println("当前Spring 应用上下文的类:" + context.getClass().getName()); 
    }
}

配置Spring Boot源

​ 理解Spring Boot 配置 –> 类比Spring配置

ConfigFileApplicationListener

管理配置文件,比如:application.properties 以及 application.yaml

application-{profile}.properties:

profile = dev 、test

  1. application-{profile}.properties
  2. application.properties

SpringAppliation 类型推断(SpringBoot 2.X)

​ 判断Web 应用类型(REACTIVENONESERVLET) 源码阅读:

private WebApplicationType deduceWebApplicationType() {
    if (ClassUtils.isPresent("org.springframework.web.reactive.DispatcherHandler", (ClassLoader)null) && !ClassUtils.isPresent("org.springframework.web.servlet.DispatcherServlet", (ClassLoader)null) && !ClassUtils.isPresent("org.glassfish.jersey.server.ResourceConfig", (ClassLoader)null)) {
        return WebApplicationType.REACTIVE;
    } else {
        String[] var1 = WEB_ENVIRONMENT_CLASSES;
        int var2 = var1.length;

        for(int var3 = 0; var3 < var2; ++var3) {
            String className = var1[var3];
            if (!ClassUtils.isPresent(className, (ClassLoader)null)) {
                return WebApplicationType.NONE;
            }
        }
        return WebApplicationType.SERVLET;
    }
}

Spring Boot 事件

​ 介绍 Spring Boot 事件与 Spring Framework 事件之间的差异和联系

参考:GP-小马哥


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