一、SpringApplication
介绍SpringApplication启动,用Spring实现类似的功能。
1.自定义 SpringApplication (Spring)
介绍 SpringApplication SpringApplicationBuilder API 调整
The
SpringApplicationclass provides a convenient way to bootstrap a Spring application that is started from amain()method. In many situations, you can delegate to the staticSpringApplication.runmethod
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Tomcat和SpringMVC的依赖，类似于子项目自动添加父项目的依赖。
1.1@Component 的“派生性”
@Componentis a generic stereotype for any Spring-managed component. Any component annotated with@Componentis a candidate for component scanning. Similarly, any component annotated with an annotation that is itself meta-annotated with@Componentis also a candidate for component scanning. For example,@Serviceis 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-
ClassPathScanningCandidateComponentProviderprotected 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);
1.2. 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());
}
}
2.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
application-{profile}.properties- application.properties
3.SpringAppliation 类型推断（SpringBoot 2.X)
判断Web 应用类型（REACTIVE、NONE、SERVLET） 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;
}
}
4.Spring Boot 事件
介绍 Spring Boot 事件与 Spring Framework 事件之间的差异和联系