THTTPApplication object is not responding UI
lazarus / 38-Networking and Web Programming

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Packs · 2023-06-26 18:25

I have create one windows gui application

myhttpapp: THTTPApplication;     ( defined variable )


inside form create event created object
myhttpapp := THTTPApplication.Create(FrmMarksheet);

  myhttpapp.Port := 5008;
  HTTPRouter.RegisterRoute('/time', @timeEndpoint);
  myhttpapp.Threaded:= false ;
  myhttpapp.Initialize;
  myhttpapp.StopOnException:= true;
  myhttpapp.Run; 


this code is giving response , but my main window is not responding .


what is the mistake

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delphius · 2023-06-26 18:40

Based on the code you provided, it seems that you are creating an
instance of `THTTPApplication` and running it in your main window's
create event. However, since `THTTPApplication.Run` is a blocking
method, it will prevent the main window from responding to user
interactions until the application is stopped or an exception occurs.

To allow your main window to remain responsive while running the
`THTTPApplication`, you can run it in a separate thread. Here's an
example of how you can achieve this:

1. Create a new unit (e.g., `HttpServerThread.pas`) that will contain
the code for running the HTTP server in a separate thread.

2. In this unit, define a new class that inherits from `TThread`,
let's call it `THttpServerThread`. Override the `Execute` method to
contain the code for initializing and running the `THTTPApplication`.
Here's an example implementation:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i unit
HttpServerThread; interface uses  Classes, HTTPApp; type 
THttpServerThread = class(TThread)  private    myhttpapp:
THTTPApplication;  protected    procedure Execute; override;  public 
 constructor Create;    destructor Destroy; override; 
end; implementation uses  FrmMarksheet; // Make sure the unit
containing your main window form is included here procedure
THttpServerThread.Execute;begin  myhttpapp :=
THTTPApplication.Create(FrmMarksheet);  myhttpapp.Port := 5008; 
HTTPRouter.RegisterRoute('/time', @timeEndpoint);  myhttpapp.Threaded
:= False;  myhttpapp.Initialize;  myhttpapp.StopOnException := True; 
myhttpapp.Run;  FreeAndNil(myhttpapp);end; constructor
THttpServerThread.Create;begin  inherited Create(False); // Create the
thread in a suspended stateend; destructor
THttpServerThread.Destroy;begin  Terminate; // Terminate the thread
when it is being destroyed  inherited Destroy;end; end.
3. Modify your main window's code to create an instance of
`THttpServerThread` and start it. This will run the HTTP server in a
separate thread, allowing your main window to remain responsive.
Here's an example:


Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i uses  ...,
HttpServerThread; ... procedure TForm1.FormCreate(Sender:
TObject);begin  THttpServerThread.Create; // Create and start the HTTP
server threadend;

By running the HTTP server in a separate thread, your main window
should remain responsive while the server is running and handling
incoming requests.

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Packs · 2023-06-26 19:16

Thank So much for your quick response. It is working .

I have following doubts .

Why you want reference of mainform( frmmarksheet)inside execute method
why you have used freeandnil .

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delphius · 2023-06-27 17:49

Quote from: Prakash on June 26, 2023, 09:16:53 pmWhy you want
reference of mainform( frmmarksheet)

The `THTTPApplication` class is part of the HTTPApp unit. It is
responsible for handling HTTP requests and managing the HTTP server
functionality. When you create an instance of `THTTPApplication`, it
needs to be associated with a form or a component that will serve as
the main application container.

By passing `FrmMarksheet` as the parameter when creating
`THTTPApplication`, you are associating the HTTP server with your main
form. This allows the HTTP server to be aware of the main form's
existence and interact with it if necessary.

In some cases, the HTTP server may need to access or modify
properties, components, or functionality provided by the main form.
For example, it might need to display information or perform some
action based on user input received through HTTP requests. By
referencing the main form when creating `THTTPApplication`, you
establish a connection between the HTTP server and the main form,
enabling such interactions.

In your specific code snippet, it seems like you want the HTTP server
to be integrated into your main application window (`FrmMarksheet`).
By associating `THTTPApplication` with `FrmMarksheet`, the HTTP server
becomes part of your application, and any requests or responses it
handles can be coordinated within the context of your main form.

Overall, passing the main form as a parameter when creating
`THTTPApplication` allows for seamless integration between the HTTP
server functionality and the rest of your application, enabling
communication and interaction between the server and your main form.

And now, considering the above, and answering the essence of the
question, in order to get access to FrmMarksheet, you need to connect
a module with the form to uses, and it was added to the implementation
section specifically so that the compiler does not swear at cyclic
links between modules.

Quote from: Prakash on June 26, 2023, 09:16:53 pminside execute method
why you have used freeandnil .

When you create an object using the `Create` operator, like in your
case:


Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i myhttpapp
:= THTTPApplication.Create(FrmMarksheet);

An instance of the `THTTPApplication` class is created in memory. The
`myhttpapp` object references this instance, allowing you to access
and manipulate it.

However, when you're done with the `myhttpapp` object and want to free
the memory it occupies, you need to properly release the object. This
is done using the `Free` operator, which calls the object's destructor
and frees the memory it occupies:


Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
myhttpapp.Free;

However, when an object is freed using `Free`, the pointer to it still
remains valid, meaning it still points to the deallocated object. This
can lead to errors and unexpected behavior if you attempt to use the
pointer after it has been freed.

To avoid this problem, it's recommended to use `FreeAndNil`. This
function does two things:

1. Frees the memory occupied by the object by calling `Free`.
2. Sets the pointer to `nil`, indicating that the object no longer
exists.

Therefore, calling `FreeAndNil(myhttpapp);` removes the `myhttpapp`
object and ensures that the `myhttpapp` pointer no longer points to an
invalid object. This prevents potential errors when trying to use the
object after it has been freed.

It's important to note that using `FreeAndNil` is not mandatory, but
it's good practice to prevent potential memory and pointer issues.