SpringBoot系列（八）---- 启动配置原理

启动配置原理

• 一般我们的配置核心是在各个配置的META-INF/spring.factories中，而我们SpringBoot的启动相关是、

  • ApplicationContextInitializer

  • SpringApplicationRunListener

• 只需要放在ioc容器中

  • ApplicationRunner

  • CommandLineRunner

启动流程

• 创建SpringApplication对象

initialize(sources);
private void initialize(Object[] sources) {
    
    
    //保存主配置类
    if (sources != null && sources.length > 0) {
    
    
        this.sources.addAll(Arrays.asList(sources));
    }
    //判断当前是否一个web应用
    this.webEnvironment = deduceWebEnvironment();
    //从类路径下找到META-INF/spring.factories配置的所有ApplicationContextInitializer；然后保存起来
    setInitializers((Collection) getSpringFactoriesInstances(
        ApplicationContextInitializer.class));
    //从类路径下找到ETA-INF/spring.factories配置的所有ApplicationListener
    setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
    //从多个配置类中找到有main方法的主配置类
    this.mainApplicationClass = deduceMainApplicationClass();
}

• 运行run方法

public ConfigurableApplicationContext run(String... args) {
    
    
   StopWatch stopWatch = new StopWatch();
   stopWatch.start();
   ConfigurableApplicationContext context = null;
   FailureAnalyzers analyzers = null;
   configureHeadlessProperty();
    
   //获取SpringApplicationRunListeners；从类路径下META-INF/spring.factories
   SpringApplicationRunListeners listeners = getRunListeners(args);
    //回调所有的获取SpringApplicationRunListener.starting()方法
   listeners.starting();
   try {
    
    
       //封装命令行参数
      ApplicationArguments applicationArguments = new DefaultApplicationArguments(
            args);
      //准备环境
      ConfigurableEnvironment environment = prepareEnvironment(listeners,
            applicationArguments);
       		//创建环境完成后回调SpringApplicationRunListener.environmentPrepared()；表示环境准备完成
       
      Banner printedBanner = printBanner(environment);
       
       //创建ApplicationContext；决定创建web的ioc还是普通的ioc
      context = createApplicationContext();
       
      analyzers = new FailureAnalyzers(context);
       //准备上下文环境;将environment保存到ioc中；而且applyInitializers()；
       //applyInitializers()：回调之前保存的所有的ApplicationContextInitializer的initialize方法
       //回调所有的SpringApplicationRunListener的contextPrepared()；
       //
      prepareContext(context, environment, listeners, applicationArguments,
            printedBanner);
       //prepareContext运行完成以后回调所有的SpringApplicationRunListener的contextLoaded（）；
       
       //s刷新容器；ioc容器初始化（如果是web应用还会创建嵌入式的Tomcat）；Spring注解版
       //扫描，创建，加载所有组件的地方；（配置类，组件，自动配置）
      refreshContext(context);
       //从ioc容器中获取所有的ApplicationRunner和CommandLineRunner进行回调
       //ApplicationRunner先回调，CommandLineRunner再回调
      afterRefresh(context, applicationArguments);
       //所有的SpringApplicationRunListener回调finished方法
      listeners.finished(context, null);
      stopWatch.stop();
      if (this.logStartupInfo) {
    
    
         new StartupInfoLogger(this.mainApplicationClass)
               .logStarted(getApplicationLog(), stopWatch);
      }
       //整个SpringBoot应用启动完成以后返回启动的ioc容器；
      return context;
   }
   catch (Throwable ex) {
    
    
      handleRunFailure(context, listeners, analyzers, ex);
      throw new IllegalStateException(ex);
   }
}

事件监听机制

配置在META-INF/spring.factories

• ApplicationContextInitializer

public class HelloApplicationContextInitializer implements ApplicationContextInitializer<ConfigurableApplicationContext> {
    
    
    @Override
    public void initialize(ConfigurableApplicationContext applicationContext) {
    
    
        System.out.println("ApplicationContextInitializer...initialize..."+applicationContext);
    }
}

• SpringApplicationRunListener

public class HelloSpringApplicationRunListener implements SpringApplicationRunListener {
    
    

    //必须有的构造器
    public HelloSpringApplicationRunListener(SpringApplication application, String[] args){
    
    

    }

    @Override
    public void starting() {
    
    
        System.out.println("SpringApplicationRunListener...starting...");
    }

    @Override
    public void environmentPrepared(ConfigurableEnvironment environment) {
    
    
        Object o = environment.getSystemProperties().get("os.name");
        System.out.println("SpringApplicationRunListener...environmentPrepared.."+o);
    }

    @Override
    public void contextPrepared(ConfigurableApplicationContext context) {
    
    
        System.out.println("SpringApplicationRunListener...contextPrepared...");
    }

    @Override
    public void contextLoaded(ConfigurableApplicationContext context) {
    
    
        System.out.println("SpringApplicationRunListener...contextLoaded...");
    }

    @Override
    public void finished(ConfigurableApplicationContext context, Throwable exception) {
    
    
        System.out.println("SpringApplicationRunListener...finished...");
    }
}

• 配置（META-INF/spring.factories）

org.springframework.context.ApplicationContextInitializer=\
com.atguigu.springboot.listener.HelloApplicationContextInitializer

org.springframework.boot.SpringApplicationRunListener=\
com.atguigu.springboot.listener.HelloSpringApplicationRunListener

只需要放在ioc容器中

• ApplicationRunner

@Component
public class HelloApplicationRunner implements ApplicationRunner {
    
    
    @Override
    public void run(ApplicationArguments args) throws Exception {
    
    
        System.out.println("ApplicationRunner...run....");
    }
}

CommandLineRunner

@Component
public class HelloCommandLineRunner implements CommandLineRunner {
    
    
    @Override
    public void run(String... args) throws Exception {
    
    
        System.out.println("CommandLineRunner...run..."+ Arrays.asList(args));
    }
}

自定义starter

• 新建一个普通Maven模块：springboot-starter1
  
• 新建一个Springboot模块：springboot-starter-autoconfigure
  
• 点击apply即可，基本结构
  
• 在我们的 starter1 中 导入 autoconfigure 的依赖！

<!-- 启动器 -->
<dependencies>
<!--  引入自动配置模块 -->
    <dependency>
        <groupId>com.cz</groupId>
        <artifactId>springboot-starter-autoconfigure</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    </dependency>
</dependencies>

• 将 autoconfigure 项目下多余的文件都删掉，Pom中只留下一个 starter，这是所有的启动器基本配置！
  
• 我们编写一个自己的服务

public class HelloService {
    
    

    HelloProperties helloProperties;

    public HelloProperties getHelloProperties() {
    
    
        return helloProperties;
    }

    public void setHelloProperties(HelloProperties helloProperties) {
    
    
        this.helloProperties = helloProperties;
    }

    public String sayHello(String name){
    
    
        return helloProperties.getPrefix() + name + helloProperties.getSuffix();
    }

}

• 编写HelloProperties 配置类

@ConfigurationProperties(prefix = "cz.hello")
public class HelloProperties {
    
    

    private String prefix;
    private String suffix;

    public String getPrefix() {
    
    
        return prefix;
    }

    public void setPrefix(String prefix) {
    
    
        this.prefix = prefix;
    }

    public String getSuffix() {
    
    
        return suffix;
    }

    public void setSuffix(String suffix) {
    
    
        this.suffix = suffix;
    }
}

• 编写我们的自动配置类并注入bean，测试！

@Configuration
@ConditionalOnWebApplication //web应用生效
@EnableConfigurationProperties(HelloProperties.class)
public class HelloServiceAutoConfiguration {
    
    

    @Autowired
    HelloProperties helloProperties;

    @Bean
    public HelloService helloService(){
    
    
        HelloService service = new HelloService();
        service.setHelloProperties(helloProperties);
        return service;
    }
}

• 在resources编写一个自己的 META-INF\spring.factories

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
  com.cz.starter.HelloServiceAutoConfiguration

• 编写完成后，可以安装到maven仓库中！