MARS, angular, firedac, json

[Jean Vandromme 0]

I try since several days now to get a json array from a dataset query from a MARS server (FiredacBasic demo)

If I use a simple dataset like this:

[GET, Path('/employees'), Produces(TMediaType.APPLICATION_JSON), IsReference]
function getEmployees: TFDDataSet;

 

function TMainDataResource.getEmployees: TFDDataSet;
begin
  Result := qEmployees;
end;

 

I get this in chrome:

 

this in Postman:

 

this error in Angular with a simple call like this:

  getEmployees(): Observable<Employee> {
    return this.http.get<Employee>('http://localhost:8080/rest/default/maindata/employees')
    .pipe(
      tap(data => console.log(data))
    );
  }

 

 

If I use a datasets array:

[GET, Path('/employees'), Produces(TMediaType.APPLICATION_JSON), IsReference]
 function getEmployees: TArray<TFDDataSet>;

 

function TMainDataResource.getEmployees: TArray<TFDDataSet>;
begin
  Result := [qEmployees];
end;

 

I get this in chrome:

 

this in postman:

 

and no error in angular:

 

Any clue how to solve this ?

 

Thanks

[Andrea Magni 75]

Hi @Jean Vandromme,

I am sorry to have so little time to help you these days. Hope will get some more next week.

In the meantime, please try to examine the XHR request made by Angular in the Chrome development tools.

In the "Network" pane of Chrome's Development tools you should see the http call that fails.

Right click on the request (in the left panel) and select "Copy -> Copy as cURL") then paste it here. It should look like:

curl 'https://en.delphipraxis.net/topic/1091-mars-angular-firedac-json/' ' -H 'Origin: https://en.delphipraxis.net' -H 'Accept-Encoding: gzip, deflate, br' -H 'Accept-Language: it-IT,it;q=0.9,en-US;q=0.8,en;q=0.7' -H 'User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.131 Safari/537.36' -H 'Content-Type: application/x-www-form-urlencoded; charset=UTF-8' -H 'Accept: application/json, text/javascript, */*; q=0.01' -H 'Referer: https://en.delphipraxis.net/topic/1091-mars-angular-firedac-json/' -H 'X-Requested-With: XMLHttpRequest' -H 'Connection: keep-alive' --compressed

 

 

This may help as we can check together if there's some particularities in the actual request.

Another thing you should try is to debug the REST server in Delphi. Remember to select the "Debug" configuration for your Delphi project (this should also add some more specific informations to the error message you are getting).

 

Hope to hear from you soon.

 

Sincerely,

Andrea

[Jean Vandromme 0]

Here is the XHR request

 

curl "http://localhost:8080/rest/default/maindata/employees" -H "Accept: application/json, text/plain, */*" -H "Referer: http://localhost:4200/employees-list" -H "Origin: http://localhost:4200" -H "User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.131 Safari/537.36" --compressed

[Jean Vandromme 0]

The differences between the 2 responses (array vs no array) from MARS is the content-type:

with array: Content-Type=*/*

without array: Content-Type=text/plain; charset=ISO-8859-1

[Jean Vandromme 0]

Here are the 2 printscreens:

with array:

 

without:

[Andrea Magni 75]

Do you have a chance to debug the server (run the server application with the debugger)?

Or at least recompile the server in Debug configuration (that should give us some more error details, more than "Internal server error").

 

I think the problem may be that Accept value...

 

Sincerely,

Andrea 

[Jean Vandromme 0]

There's a DOMException with message 'Microsoft MSXML is not installed' ?

MSXML 3,4,5 and 6 are installed

I run a Windows 10 Family OS

 

[Jean Vandromme 0]

You were right (again, like always 🙂

I add in my GET call in angular an option for content:

 

  httpOptions = {
    headers: new HttpHeaders({
      'Content-Type': 'application/json',
      'Accept': 'application/json'
    })
  }  

  getEmployees(): Observable<any> {
    return this.http.get<any>('http://localhost:8080/rest/default/maindata/employees', this.httpOptions)
    .pipe(
      tap(data => console.log(data))
    );
  }

 

and now, I get a correct json array in angular:

 

I still don't understand why it is necessary in one case and not the other ?

 

Thanks again,

Hope it will help others

  

[Andrea Magni 75]

Glad you worked around this.

I believe (I need to replicate this and investigate a bit) the Accept header sent from Angular matches also some MARS XML serializer.

 

Will let you know here as soon as I figure out what's happening.

 

Thanks!

 

Andrea

[Andrea Magni 75]

On 5/16/2019 at 6:24 PM, Andrea Magni said:

I believe (I need to replicate this and investigate a bit) the Accept header sent from Angular matches also some MARS XML serializer.

Will let you know here as soon as I figure out what's happening.

 

 

It turned out it was the wildcard in the Accept header to cause this.

I just pushed a fix that should also apply to your case and you may no longer need to instruct the Accept header all the times.

Branch: develop, link to the commit: https://github.com/andrea-magni/MARS/commit/b8d5768b65072ff403de3c60e17688e8e95b1d9a

 

Sincerely,

Andrea