JSON in Delphi with examples

As more developers look to create programs that can run on several operating systems, cross-platform application development has grown in popularity. In cross-platform development, controlling application settings is a crucial step. With some helpful components and examples, we’ll go over how to utilize JSON to store application settings in Delphi in this post.

What is JSON?

JSON (JavaScript Object Notation) is a simple data exchange format that is simple for both humans and machines to read, write, parse, and produce. Although it is built on a portion of JavaScript, it is not dependent on JavaScript to function.

JSON is frequently used in web applications to store configuration information and other settings, but it may also be utilized in desktop and mobile apps. JSON can be used in Delphi to store application settings that are simple to read and write on several platforms.

Using JSON to Store Application Settings in Delphi

You must use a JSON library or component in Delphi to use JSON to store application settings. SuperObject, DelphiJSON, and mORMot are just a few of the free and open source JSON components that are readily available for Delphi.

After selecting a JSON component, you can begin storing and retrieving application settings using it. Here is an illustration of how to use SuperObject to store and retrieve application settings:

uses

SuperObject;

procedure SaveSettings;

var

Settings: ISuperObject;

begin

Settings := TSuperObject.Create;

Settings.S[‘Username’] := ‘John’;

Settings.S[‘Password’] := ‘mypassword’;

Settings.I[‘Port’] := 8080;

Settings.B[‘RememberMe’] := True;

Settings.SaveTo(‘settings.json’);

end;

procedure LoadSettings;

var

Settings: ISuperObject;

begin

Settings := TSuperObject.Create;

Settings.LoadFromFile(‘settings.json’);

ShowMessage(Settings.S[‘Username’]);

ShowMessage(Settings.S[‘Password’]);

ShowMessage(IntToStr(Settings.I[‘Port’]));

ShowMessage(BoolToStr(Settings.B[‘RememberMe’], True));

end;

In this illustration, the application settings are stored in a brand-new TSuperObject. A username, password, port number, and a boolean flag to remember the user were then set as values for the settings. The settings are then saved to a file called settings.json.

We import the settings.json file into a new TSuperObject to retrieve the settings, and then we use the S, I, and B properties to get the settings’ values.

Free JSON Components for Delphi

To save and retrieve application settings, you can use the following free JSON components for Delphi:

A quick and efficient JSON library for Delphi called SuperObject.

DelphiJSON is a straightforward and user-friendly JSON library for Delphi.

mORMot: A robust and adaptable open source Delphi framework that supports JSON.

Example 1: Reading JSON Data from a URL

You can use Delphi’s TNetHTTPClient component to retrieve JSON data from a URL. Here’s an example of how to retrieve JSON data from the OpenWeatherMap API:

uses

System.Net.HttpClient, System.JSON;

procedure GetWeatherData;

var

Client: TNetHTTPClient;

Response: IHTTPResponse;

JSONData: TJSONObject;

begin

Client := TNetHTTPClient.Create(nil);

try

Response := Client.Get(‘https://api.openweathermap.org/data/2.5/weather?q=New%20York&appid=YOURAPPID’);

if Response.StatusCode = 200 then

begin

JSONData := TJSONObject.ParseJSONValue(Response.ContentAsString) as TJSONObject;

ShowMessage(JSONData.GetValue(‘name’).Value);

ShowMessage(JSONData.Get(‘weather’).JsonValue.ToString);

ShowMessage(JSONData.Get(‘main’).GetValue(‘temp’).Value);

end;

finally

Client.Free;

end;

end;

In this example, we use TNetHTTPClient to retrieve JSON data from the OpenWeatherMap API. We then parse the JSON data using Delphi’s built-in TJSONObject class and display some of the data in a message box.

Example 2: Writing JSON Data to a File

You can use Delphi’s TStreamWriter component to write JSON data to a file. Here’s an example of how to create a JSON file with some sample data:

uses

System.JSON, System.Classes;

procedure WriteJSONToFile;

var

Writer: TStreamWriter;

JSONData: TJSONObject;

begin

JSONData := TJSONObject.Create;

JSONData.AddPair(‘name’, ‘John’);

JSONData.AddPair(‘age’, TJSONNumber.Create(30));

JSONData.AddPair(‘isMarried’, TJSONBool.Create(True));

Writer := TStreamWriter.Create(‘sample.json’);

try

Writer.Write(JSONData.ToString);

finally

Writer.Free;

end;

end;

In this example, we create a new TJSONObject with some sample data (a name, age, and marital status). We then create a new TStreamWriter to write the JSON data to a file called sample.json.

Example 3: Executing a JSON-RPC Call

JSON-RPC is a remote procedure call (RPC) protocol encoded in JSON. You can use Delphi’s TIdHTTP component to execute a JSON-RPC call. Here’s an example of how to execute a JSON-RPC call using the Blockchain.info API:

uses

IdHTTP, IdGlobal, System.JSON;

procedure ExecuteJSONRPC;

var

IdHTTP: TIdHTTP;

JSONRequest: TJSONObject;

JSONResponse: TJSONObject;

ResponseString: string;

begin

IdHTTP := TIdHTTP.Create(nil);

try

JSONRequest := TJSONObject.Create;

JSONRequest.AddPair(‘method’, ‘blockchain.info/latestblock’);

JSONRequest.AddPair(‘params’, TJSONArray.Create);

ResponseString := IdHTTP.Post(‘https://blockchain.info/‘, JSONRequest.ToString, IndyTextEncoding_UTF8);

JSONResponse := TJSONObject.ParseJSONValue(ResponseString) as TJSONObject;

ShowMessage(JSONResponse.GetValue(‘hash’).Value);

finally

IdHTTP.Free;

end;

end;

In this example, we use TIdHTTP to execute a JSON-RPC call to the Blockchain.info API. We build a new JSON request using Delphi’s TJSONObject class and add the method and params values. We then use TIdHTTP to post the JSON request to the API and receive a response. Finally, we parse the JSON response using TJSONObject.ParseJSONValue and display some of the data in a message box.

These are just a few examples of how to read, write, and execute JSON in Delphi. There are many more use cases for JSON, including serialization, deserialization, and data storage. To work with JSON in Delphi, you can use built-in classes such as TJSONObject and TJSONValue, as well as third-party libraries like SuperObject and mORMot.

Conclusion

Managing cross-platform development is made simple and efficient by using JSON to store application parameters in Delphi. You may quickly store and retrieve application settings in JSON format with the aid of free and open source JSON components like SuperObject, DelphiJSON, and mORMot.