environment是在printBanner之前就初始化好了, 更在context建立之前, 

已經載入application-xxxx.properties, System.properties, System.environment ...

也可以自己監聽應用啟動 SpringApplicationRunListener事件， 完成自己的獨特的配置載入方案

啟動後呼叫listener.finished() 列印一些啟動後的資訊

prepareEnvironment()原始碼如下

 1     private
 
 ConfigurableEnvironment prepareEnvironment(
 2             SpringApplicationRunListeners listeners,
 3             ApplicationArguments applicationArguments) {
 4         // Create and configure the environment
 5         ConfigurableEnvironment environment = getOrCreateEnvironment();
 6 
 7 //載入標準目錄下的配置檔案 &profile
 

 8         configureEnvironment(environment, applicationArguments.getSourceArgs());
 9 //載入自定義的配置方案
10         listeners.environmentPrepared(environment);
11         if (!this.webEnvironment) {
12             environment = new EnvironmentConverter(getClassLoader())
13                     .convertToStandardEnvironmentIfNecessary(environment);
 
14         }
15         return environment;
16     }