TdxBackendCustomInMemoryJSONConnection Class
The base class for JSON-based data connection components (TdxBackendInMemoryJSONConnection and TdxBackendDataSetJSONConnection).
Declaration
TdxBackendCustomInMemoryJSONConnection = class abstract(TdxBackendCustomDataConnection)Remarks
A data connection component allows you to bind a backend client component to data. JSON-based Data Connection components store source data in a format compatible with the DevExpress Reports for Web engine (used as the base for TdxReport and TdxDashboardControl components).
Main API Members
The list below outlines key members of the TdxBackendCustomInMemoryJSONConnection class. These members allow you to configure core data connection settings.
Data Connection Settings
- Active
- Specifies if the data connection is active.
- DisplayName
Specifies the data connection’s name in the report/UI layout template designer and Collection Editor dialogs.
The DisplayName property value is used to specify the data connection name within report/UI layout templates.
- ConnectionString
Specifies a connection string (or stores serialized data in the JSON format).
Tip
Refer to the following topic for detailed information on JSON Data: Connection to a JSON Data Source.
- SetJSONValue
- Sets component data to the specified JSON value.
General-Purpose API Members
- Collection | Index
- Specify the parent collection component.
Code Examples
Assign JSON Data as a Connection String
The following code example demonstrates an OnClick event handler that configures a TdxBackendInMemoryJSONConnection component, assigns a table defined within a JSON string to the ConnectionString property, and displays the Dashboard Designer dialog:
uses
dxDashboard.Control, // Declares the TdxDashboardControl component
dxBackend.ConnectionString.JSON; // Declares the TdxBackendInMemoryJSONConnection component
// ...
procedure TMyForm.cxButton1Click(Sender: TObject);
begin
// Specify a user-friendly data connection name (for end-user dialogs)
dxBackendInMemoryJSONConnection1.DisplayName := 'Memory-Based JSON Data Source';
// Define a table that consists of three columns ("id", "Region", and "Sales") and five data rows
dxBackendInMemoryJSONConnection1.ConnectionString := 'Json=''' +
'[{"id": 1, "Region": "Asia", "Sales": 4.7685},' + // Row #1
'{"id": 2, "Region": "Australia", "Sales": 1.9576},' + // Row #2
'{"id": 3, "Region": "Europe", "Sales": 3.3579},' + // Row #3
'{"id": 4, "Region": "North America", "Sales": 3.7477},' + // Row #4
'{"id": 5, "Region": "South America", "Sales": 1.8237}]'''; // Row #5
dxDashboardControl1.ShowDesigner; // Displays the Dashboard Designer dialog
end;
Assign a JSON Data String Directly
The following code example demonstrates an OnClick event handler that calls the SetJSONValue procedure to assign a table defined within a JSON string to the TdxBackendInMemoryJSONConnection component and displays the Dashboard Designer dialog:
uses
dxDashboard.Control, // Declares the TdxDashboardControl component
dxBackend.ConnectionString.JSON; // Declares the TdxBackendInMemoryJSONConnection component
// ...
procedure TMyForm.cxButton1Click(Sender: TObject);
var
AJSONData: string;
begin
// Define a table that consists of three columns ("id", "Region", and "Sales") and five data rows
AJSONData :=
'[{"id": 1, "Region": "Asia", "Sales": 4.7685},' + // Row #1
'{"id": 2, "Region": "Australia", "Sales": 1.9576},' + // Row #2
'{"id": 3, "Region": "Europe", "Sales": 3.3579},' + // Row #3
'{"id": 4, "Region": "North America", "Sales": 3.7477},' + // Row #4
'{"id": 5, "Region": "South America", "Sales": 1.8237}]'; // Row #5
// Specify a user-friendly data connection name (for end-user dialogs)
dxBackendInMemoryJSONConnection1.DisplayName := 'Memory-Based JSON Data Storage';
dxBackendInMemoryJSONConnection1.SetJSONValue(AJSONData); // Assigns the defined JSON data string
dxDashboardControl1.ShowDesigner; // Displays the Dashboard Designer dialog
end;
Load JSON Data from a Remote Source
The code example in this section demonstrates an OnClick event handler that configures a TdxBackendInMemoryJSONConnection component used to load JSON data from an external source using a connection string and displays the Dashboard Designer dialog.
Note
This code example demonstrates a sample connection string. You must replace specified parameter values with required URI, username, password, access tokens, etc.
uses
dxDashboard.Control, // Declares the TdxDashboardControl component
dxBackend.ConnectionString.JSON; // Declares the TdxBackendInMemoryJSONConnection component
// ...
procedure TMyForm::cxButton1Click(Sender: TObject);
begin
dxBackendInMemoryJSONConnection1.Active := False; // Terminates the current connection (if one exists)
// Specify a user-friendly data connection name (for end-user dialogs)
dxBackendInMemoryJSONConnection1.DisplayName := 'Memory-Based JSON Data Source';
dxBackendInMemoryJSONConnection1.ConnectionString :=
'Uri=https://northwind.netcore.io/customers.json;' + // Specifies the path to a source JSON file
'Username=user;' + // Specifies a valid user name
'Password=pwd;' + // Specifies the corresponding password for the user name
'MyAuthHeader1=secretToken1;MyAuthHeader2=secretToken2;' + // Specifies authentication tokens
'query:id=123456;query:name=MyName;' // Specifies the required query ID and name
dxBackendInMemoryJSONConnection1.Active := True; // Connects to the target Web service endpoint
dxDashboardControl1.ShowDesigner(); // Displays the Dashboard Designer dialog
end;
Terminal TdxBackendCustomInMemoryJSONConnection Class Descendants
Do not use the TdxBackendCustomInMemoryJSONConnection class directly. Use the following components instead:
- TdxBackendInMemoryJSONConnection
- A component designed for interaction with data stored in memory.
- TdxBackendDataSetJSONConnection
- A component designed to fetch data from one or multiple datasets (TDataSet descendant instances).