Add ContextInitialized interface for Dev Mode only

[abdullahtellioglu]

Describe your motivation

In Copilot, certain operations need to be performed when the servlet is initialized, such as collecting classes, analyzing source code usage, etc... To do that, the best candidate method that Copilot could use is handleConnect from DevToolsMessageHandler with a loaded flag, because handleConnect is executed any time a browser tab opens.

Describe the solution you'd like

It would be better if there were an interface that Copilot could use when the servlet is initialized. The method should run only in DEV mode, so it should not affect the production build.

Describe alternatives you've considered

I do not have any solutions to propose

[mcollovati]

Couldn't it be done with a VaadinServiceInitListener?

[abdullahtellioglu]

Wouldn't it better to have a dedicated class for dev mode only?

[Legioth]

You anyways have a dedicated classpath for isolation which means that there might not be a need for any other mechanism?

[abdullahtellioglu]

You anyways have a dedicated classpath for isolation which means that there might not be a need for any other mechanism?

VaadinServiceInitListener is in flow.server. When you are developing a dev tool, you could encounter the issue of how to eagerly load data on server startup and when that happens, you would seek an interface in the same package as DevTools-related classes are. It is ambiguous whether VaadinServiceInitListener gets executed in Production or not, without starting the application in production mode

Class path isolation could ensure that classes are not exposed and created in production mode. Still, an explicit interface that is ensured by the framework that runs on DEV mode only would be self-explanatory and safer for developers to use, in my opinion.

[mcollovati]

In the VaadinServiceInitListener you can check if the app is running in production or dev mode by calling service.getDeploymentConfiguration().isProduction().

If we want to make it more explicit and move control to the Flow server, maybe we can introduce a @DevMode or @ExecutionMode(dev=true, prod=false) annotation that Flow can check when it loads contributed implementations of specific APIs.

[abdullahtellioglu]

@DevMode sounds promising, equivalent of Spring's Profile("dev")

[Legioth]

Your implementation of VaadinServiceInitListener is in your .jar file that should be on the classpath only in development.

[Legioth]

You could even go so far as to make that init listener implementation check service.getDeploymentConfiguration().isProduction() and thrown an exception if it's accidentally used in the wrong way.