B4J Question [Server] Handler Initialize Sub

Alessandro71 · Jul 25, 2025

In the Server tutorial https://www.b4x.com/android/forum/threads/server-building-web-servers-with-b4j.37172/ there's a statement about the Initialize Sub

A handler class should have an empty Initialize

Is it a mandatory requirement?

By putting code in the Initialize Sub, do I risk it not to be executed or having other side effects?

LucaMs · Jul 25, 2025

Since the instance of the handler class is not created by you, the programmer, but by B4J-jServer, I would say that Erel meant that you cannot add parameters to the Sub Initialize, which you can do with other classes.

aeric · Jul 25, 2025

Alessandro71 said:
Is it a mandatory requirement?

I think "should" doesn't mean "mandatory" but why not just leave it there.

Alessandro71 said:
By putting code in the Initialize Sub, do I risk it not to be executed or having other side effects?

I think if you put some code inside, it is expected to be executed. Otherwise it is a bug.

Alessandro71 · Jul 25, 2025

aeric said:
I think "should" doesn't mean "mandatory" but why not just leave it there.

I think if you put some code inside, it is expected to be executed. Otherwise it is a bug.

by habit I put my initialization code in the Initialize sub.
I just read that requirement after my project is already written and seemingly running fine.
Being the Handler a class, I expect Initialize to work as usual but that line made me wonder if I was braking some rule that may backfire when least expected.

aeric · Jul 25, 2025

Alessandro71 said:
by habit I put my initialization code in the Initialize sub.
I just read that requirement after my project is already written and seemingly running fine.
Being the Handler a class, I expect Initialize to work as usual but that line made me wonder if I was braking some rule that may backfire when least expected.

I also expect it is exactly the same as what a normal class is.
I also use the Initialize sub in my web api project template to initialize some objects.

B4X:

Public Sub Initialize
    HRM.Initialize
    HRM.VerboseMode = Main.app.api.VerboseMode
End Sub

Daestrum · Jul 25, 2025

Erel does too if you look at the websocket handler in a new server app, probably more of a what you put there, than don't put stuff there.

aeric · Jul 25, 2025

I think what Erel wants to bring out is the minimum boilerplate code is to have both Initialize and Handle subs inside this class.
The more important point I can see here is the Handle sub.

LucaMs · Jul 25, 2025

Since the instance of the handler class is not created by you, the programmer, but by B4J-jServer, I would say that Erel meant that you cannot add parameters to the Sub Initialize, which you can do with other classes.

Alessandro71 · Jul 25, 2025

LucaMs said:
Since the instance of the handler class is not created by you, the programmer, but by B4J-jServer, I would say that Erel meant that you cannot add parameters to the Sub Initialize, which you can do with other classes.

that sounds good to me: "empty" Initialize has the meaning of "empty parameters list" rather then "no code inside"

LucaMs · Jul 25, 2025

Alessandro71 said:
that sounds good to me: "empty" Initialize has the meaning of "empty parameters list" rather then "no code inside"

If we want to be precise: "Sub Initialize's signature must be exactly that, with no parameters."

B4J Question [Server] Handler Initialize Sub

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