Datasnap Xe2 Pdf Download [PORTABLE]

How to Download PDF Files Using DataSnap XE2

DataSnap XE2 is a technology that allows you to create multi-tier applications with Delphi. One of the features of DataSnap XE2 is the ability to stream files from the server to the client using TStream objects. This can be useful for transferring PDF files or other binary data over the network.

In this article, we will show you how to write a DataSnap server method that returns a TStream object containing a PDF file, and how to call this method from a DataSnap client application and save the stream to a local file.

DataSnap Server Method

The DataSnap server method that returns a TStream object is very simple. It takes a string parameter that specifies the file path of the PDF file on the server, and creates a TFileStream object to read the file. Then it returns the TFileStream object as the result of the method. Here is an example of such a method:

function TServerMethods.DownloadFile(sFilePath: string): TStream;

var

strFileStream: TFileStream;

begin

strFileStream := TFileStream.Create(sFilePath, fmOpenRead or fmShareDenyWrite);

Result := strFileStream;

end;

Note that you need to include System.Classes and System.SysUtils in the uses clause of the unit where you define this method.

DataSnap Client Application

The DataSnap client application that calls the server method and saves the stream to a local file is also very simple. It uses a TSQLConnection component to connect to the DataSnap server, and a TServerMethodsClient class to access the server methods. The TServerMethodsClient class is generated automatically by the DataSnap proxy generator tool, which you can invoke by right-clicking on the TSQLConnection component and selecting Generate DataSnap Client Classes.

Here is an example of how to call the DownloadFile method from the client application:

procedure TForm1.Button1Click(Sender: TObject);

var

ServerMethods: TServerMethodsClient;

Stream: TStream;

begin

// Connect to the DataSnap server

SQLConnection1.Open;

// Create an instance of the server methods class

ServerMethods := TServerMethodsClient.Create(SQLConnection1.DBXConnection);

try

// Call the DownloadFile method and get the stream

Stream := ServerMethods.DownloadFile('C:\\Temp\\test.pdf');

try

// Save the stream to a local file

Stream.SaveToFile('C:\\Temp\\test_copy.pdf');

finally

// Free the stream

Stream.Free;

end;

finally

// Free the server methods class

ServerMethods.Free;

end;

// Disconnect from the DataSnap server

SQLConnection1.Close;

end;

Note that you need to include Datasnap.DSClientRest in the uses clause of the unit where you use this code.

Conclusion

In this article, we have shown you how to download PDF files using DataSnap XE2. This technique can be applied to any type of files that you want to transfer from the server to the client using TStream objects. You can also use other types of streams, such as TMemoryStream or TBlobStream, depending on your needs.

If you want to learn more about DataSnap XE2, you can check out some of these resources:

DataSnap XE2 Development Essentials by Bob Swart

Delphi XE2 DataSnap 2nd by angdrake

Delphi XE2 DataSnap - Streaming JPEG Files via TStream From Server To Client by Stack Overflow user RRUZ aa16f39245