Sometimes we need create many reports in
multiple threads simultaneously. This may be the development of a web service,
or output information from an existing multithreaded application in a certain
needed document format (PDF as example).
I noted that FastReport VCL library is a
better solution for document generation in multiple formats. This component
library is easy to use and has a convenient report designer which allows you to
easily connect to different data sources, among which may be internal
application data - arrays, sets of parameters, etc.
Traditional use of FastReport does not give
any difficulties, but now we have to use this report generator in a
multithreaded application. The output file format will be PDF.
TfrxReport class has a description of several
properties which need to be set immediately after the creation of the object.
You need to remember that the object must work
in a thread without the creation of dialogs, progress bars and other visual
Here is an example of creating and setting an
object of class TfrxReport before the execution of the report:
// create report
FReport := TfrxReport.Create(nil);
// disable all messages
FReport.EngineOptions.SilentMode := True;
// enable safe work in threads
FReport.EngineOptions.EnableThreadSafe := True;
// disable cache
FReport.EngineOptions.UseFileCache := false;
// disable progress bar
FReport.ShowProgress := False;
Some reports have integrated dialog forms, and
showing them should be banned for obvious reasons. We need to override an
event handler TfrxReport.Engine.OnRunDialog by the procedure ShowReportDialog
for to any dialogs.
// handle all dialogs by ShowReportDialog
FReport.Engine.OnRunDialog := ShowReportDialog;
Our procedure will be executed instead of
showing each report dialog. We can change the state of any control in a dialog,
but we will leave this procedure empty.
procedure TTestThread.ShowReportDialog(Page: TfrxDialogPage);
Then we create an object of TfrxPDFExport and
disable the showing of dialog window and progress bar.
PDF := TfrxPDFExport.Create(nil);
PDF.ShowDialog := False;
PDF.ShowProgress := False;
All operations on the creation and exporting
of report objects can be done in the constructor of the thread. The destructor
of the thread should look like:
// destroy all created objects
Necessary objects are created and configured.
Now you can load the report template from a file and run a report in the
implementation of the main thread procedure Execute. There, it will also be
exported to the desired format.
// load report template
// set report variables
FReport.Variables['ThreadID'] := QuotedStr(FId);
// run report
if FReport.PrepareReport then
// save result in PDF
PDF.FileName := FOutPath + '\report_'+ FId +
'_' + FormatDateTime('YYYYYMMDDHHMMSS', Now) + '.pdf';
Try building reports without using RichText
objects because by so doing you can get an unstable application.
Do not forget to include ActiveX controls in
uses module, and add a call to CoInitialize (nil); in the procedure Execute
before creating a report if the report is connected to ADO. Call to
CoUninitialize at the end of the thread procedure.
// thread function</span>
// initialize COM library in current thread
// load report template from the file
// Uninitialize COM
You can see an attached example with the
application which creates 10 reports in multiple threads and write many PDF