start method will first determine whether it holds Server reference is null, otherwise they will be called once the load method, or if is null, it will end the application (System.exit (1);).
Start method is called Server.
JVM shutdown hook to add.
start @ StandardServer
Call the init method Service.
Start @ Standard Service
Call start method Engine, mapperListener and the connector.
start @ Engine
Asynchronous calls the sub-container (in this case, start the Host method).
start @ StandardHost
If there are no Host filter chain org.apache.catalina.valves.ErrorReportValve, then it is added to it.
Asynchronous calls the sub-container (in this case, the start method of Context).
start @ StandardContext
226 lines of code to do a lot of work Context configuration, start the Session Manager, start the Pipeline and so on.