Entry point

Every application has an entry point, in SenseJS, an entry point is defined as a module.

Applications can be divided into two categories: one is utility applications that run once and exits when the job is done or failed; the other is long-running applications that keep running and waiting for requests, a.k.a. daemons or servers.

Utility applications

In SenseJS, such an application can be started through:

@Module({ requires: [OtherModules] })
class MyApp {
    main() {
    }
}

ApplicationRunner.instance.run(MyApp, 'main');

the second argument of ApplicationRunner.instance.run is the name of the entry function. Once the control-flow leaves the main function, the framework will destroy all components and exit the process.

Daemon applications

Such an application can be started through:

@Module({ requires: [OtherModules] })
class MyApp {
    @OnModuleStart()
    onModuleStart() {
        // Start listening for requests
    }
    @OnModuleStop()
    onModuleStop() {
        // Stop listening for requests
    }
}
ApplicationRunner.instance.start(MyApp);

In addition to the @OnModuleCreated/@OnModuleDestroyed hooks, applications running in this way will also invoke @OnModuleStart/@OnModuleStop.

Such an app will not exit until ProcessManager.exit() is called or any exit signals are received. SenseJS also ensures all @OnModuleStop hooks are invoked before the app exits.

Conclusion

A typical SenseJS application is a collection of modules. Some modules are organizing injectables, while some modules are managing initialization and de-initialization of I/O resources, and an entry module that depends on all the others. Based on the dependency graph of all the modules, SenseJS can gracefully start up and shut down your application.