TdxBackendDataSetJSONConnection Class

A component designed to fetch data from one or multiple datasets (TDataSet descendant instances).

Declaration

TdxBackendDataSetJSONConnection = class(
    TdxBackendCustomInMemoryJSONConnection
)

Remarks

TdxBackendDataSetJSONConnection is a data connection component designed to bind a backend client component to one or multiple datasets (TdxMemData, TFDTable, TFDQuery, etc.) like any other data-aware VCL control (TcxGrid, for instance).

The TdxBackendDataSetJSONConnection component serializes data from associated datasets and stores it in memory in the JSON format^[1] compatible with the DevExpress Reports for Web engine (used as the base for TdxReport).

Main API Members

The list below outlines key members of the TdxBackendDataSetJSONConnection class. These members allow you to configure data connection settings.

Data Connection Settings

Active: Specifies if the data connection is active.
AutoRefreshData: Specifies if the data connection component automatically reloads data from associated datasets every time a backend client component starts to populate placeholders with data.
DisplayName: Specifies the data connection’s name in both designer and Collection Editor dialogs.
ConnectionString: Provides access to serialized data (in the JSON format) from associated datasets. Use the DataSets property to manage the source dataset collection.
DataSets: Allows you to manage source datasets.

General-Purpose API Members

Collection | Index: Specify the parent collection component.

Code Example: Load and Populate Report Templates from Datasets

This code example loads an XML-based report template (REPX) from a dataset, configures export settings, populates the template with data from another dataset, and displays the report preview:

Delphi
C++

uses
  dxReport,  // Declares the TdxReport component and related types
  dxBackend.ConnectionString.JSON.DataSet;  // Declares the TdxBackendDataSetJSONConnection component
// ...

procedure TMyForm.Button1Click(Sender: TObject);
var
  ADataConnection: TdxBackendDataSetJSONConnection;
  AReport: TdxReport;
  ALayoutStream: TStream;
begin
  ADataConnection := TdxBackendDataSetJSONConnection.Create(Self);
  try
    ADataConnection.Name := 'DataSetJSONData';
    ADataConnection.DataSets.Add('Data', FDataSet);
    AReport := TdxReport.Create(Self);
    try
      AReport.ReportName := 'Report';
      ALayoutStream := FLayoutDataSet.CreateBlobStream(FLayoutDataSet.FieldByName('Layout'), bmRead);
      try
        AReport.Layout.LoadFromStream(ALayoutStream);
      finally
        ALayoutStream.Free;
      end;
      AReport.Language := 'fr-FR';
      AReport.ExportFormats := [TdxReportExportFormat.PDF,
        TdxReportExportFormat.RTF, TdxReportExportFormat.HTML];
      AReport.FilterString := 'id = 5';
      AReport.ShowViewer;
    finally
      AReport.Free;
    end;
  finally
    ADataConnection.Free;
  end;
end;

#include "dxReport.hpp"  // Declares the TdxReport component and related types
#include "dxBackend.ConnectionString.JSON.DataSet.hpp" // Declares the TdxBackendDataSetJSONConnection component

// Add the following linker directives to the corresponding CPP source file:
#pragma link "dxReport"  // Required to use dxReport.hpp declarations
#pragma link "dxBackend.ConnectionString.JSON.DataSet" //Required to use TdxBackendDataSetJSONConnection declarations
// ...

void __fastcall TMyForm::Button1Click(TObject *Sender)
{
  TdxBackendDataSetJSONConnection *ADataConnection;
  TdxReport *AReport;
  TStream *ALayoutStream;
  ADataConnection = new TdxBackendDataSetJSONConnection(this);
  try
  {
    ADataConnection->Name = "DataSetJSONData";
    ADataConnection->DataSets->Add("Data", FDataSet);
    AReport = new TdxReport(this);
    try
    {
      AReport->ReportName = "Report";
      ALayoutStream = FLayoutDataSet->CreateBlobStream(FLayoutDataSet->FieldByName("Layout"), bmRead);
      try
      {
        AReport->Layout->LoadFromStream(ALayoutStream);
      }
      __finally
      {
        delete ALayoutStream;
      }
      AReport->Language = "fr-FR";
      AReport->ExportFormats = TdxReportExportFormats() << TdxReportExportFormat::PDF
        << TdxReportExportFormat::RTF << TdxReportExportFormat::HTML;
      AReport->FilterString = "id = 5";
      AReport->ShowViewer();
    }
    __finally
    {
      delete AReport;
    }
  }
  __finally
  {
    delete ADataConnection;
  }
}

Indirect TdxBackendDataSetJSONConnection Class References

The following public API members reference the TdxBackendDataSetJSONConnection class as a TdxBackendCustomDataConnection object:

TdxBackendDataConnectionCollection.Add: Creates a data connection of the required type and ads the connection to the collection.
TdxBackendDataConnectionCollection.Items: Provides indexed access to all data connection components stored in the collection.
TdxBackendDataConnectionManager.Items: Provides indexed access to stored data connection components.

Other Backend Data Connection Components

TdxBackendInMemoryJSONConnection: A component designed for interaction with data stored in memory.
TdxBackendDatabaseSQLConnection: A component designed to fetch data from an SQL database (SQL Server, PostgreSQL, SQLite, etc.).

To see TdxDashboardControl and TdxReport components in action, run BI Dashboards Designer/Viewer and Report Designer/Viewer demos in the VCL Demo Center installed with compiled VCL DevExpress demos. Click different items in the sidebar on the left to switch between demo features.

Download: Compiled VCL Demos

Tip

You can find full source code for installed compiled Report and Dashboard demos in the following folders:

%PUBLIC%\Documents\DevExpress VCL Demos\MegaDemos\Product Demos\ExpressReports\
%PUBLIC%\Documents\DevExpress VCL Demos\MegaDemos\Product Demos\ExpressDashboards\