springboo流程分析

首先加入依赖，

    
        
            org.springframework.boot
            spring-boot-dependencies
            1.5.4.RELEASE
            import
            pom
        
    



    
    org.springframework.boot
    spring-boot-starter
    

书写启动类，

@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        //实例化SpringApplication对象，然后调用run方法
        SpringApplication application = new SpringApplication(Application.class);
        ConfigurableApplicationContext context = application.run(args);

        //直接调用静态的run方法（内部转换成第一种调用方法）
        //ConfigurableApplicationContext context =SpringApplication.run(Application.class, args);
    }
}

我们知道启动类启动有二种方式第一种就是
实例化SpringApplication对象，然后调用run方法

SpringApplication application = new SpringApplication(Application.class);
ConfigurableApplicationContext context = application.run(args);

第二种就是

ConfigurableApplicationContext context =SpringApplication.run(Application.class, args);

然后我们进入第二种启动的run方法中，

再跟入run方法中

发现第二种方式就是第一种启动方式。

然后我们进入SpringApplication的构造函数中，分析一下SpringApplication的构造函数

/**
   * Create a new {@link SpringApplication} instance. The application context will load
   * beans from the specified sources (see {@link SpringApplication class-level}
   * documentation for details. The instance can be customized before calling
   * {@link #run(String...)}.
   * @param sources the bean sources
   * @see #run(Object, String[])
   * @see #SpringApplication(ResourceLoader, Object...)
   */
public SpringApplication(Object... sources) {
    initialize(sources);
}

initialize方法

private void initialize(Object[] sources) {
   if (sources != null && sources.length > 0) {
       //将启动源加入到一个set集合中
       this.sources.addAll(Arrays.asList(sources));
    }
   //判断是否是web环境
    this.webEnvironment = deduceWebEnvironment();
    //加载所有classpath下面的META-INF/spring.factories的ApplicationContextInitializer
     setInitializers((Collection) getSpringFactoriesInstances(
            ApplicationContextInitializer.class));
    //加载所有classpath下面的META-INF/spring.factories的ApplicationListener
     setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
    //推断main方法所在的类,一般是启动类
     this.mainApplicationClass = deduceMainApplicationClass();
}

sources的定义，将启动源加入到一个set集合中

private final Set