JSON support in Delphi, a simple example (refresh)

One of my old article about ITDevCon and JSON gets interest month over month. Considering that the informaion explained there are useful but quite old nowadays, I decided to write another article updating the contents available there adding also more details.


In this article we are not going to talk about event-driven (sax-style) JSON parsers.

What’s JSON

JSON (JavaScript Object Notation) has become a pivotal cornerstone in modern programming due to its simplicity, versatility, and widespread support. As a lightweight data interchange format, JSON facilitates seamless communication between diverse applications and platforms. Its human-readable structure makes it easily understandable for both developers and non-developers, fostering efficient collaboration. With the rise of web APIs and microservices architecture, JSON’s role in transmitting data has skyrocketed. Its compatibility with a wide array of programming languages empowers developers to effortlessly integrate JSON data into their projects. In a data-driven era, JSON’s importance lies in its ability to streamline data exchange, promoting interoperability and accelerating development processes.

Web Services

Foto di 3D Animation Production Company da Pixabay

JSON and Delphi

In the realm of Delphi programming, JSON (JavaScript Object Notation) stands as a crucial asset, seamlessly blending structured data representation with Delphi’s capabilities. Delphi offers built-in support for JSON through its TJSON* classes, enabling effortless parsing and creation of JSON data. This integration allows developers to efficiently handle JSON-based communication with APIs and web services, while also simplifying data manipulation within their applications. Delphi’s JSON support empowers programmers to harness the advantages of JSON’s flexibility and readability, facilitating smooth data exchange and enhancing the interoperability of their Delphi-powered solutions in today’s dynamic software landscape.

3rd Party JSON Parsers

While over the years Delphi’s JSON support improved a lot since the first version (Delphi 2009, if I remember well) some 3rd party JSON parsers may be more suitable for specific scenarios compared the the built-in. For example, Delphi’s JSON parser represent each JSON element with an object, so parsing very big JSON can lead to high memory comsuption and less speed compared with other “less elegant” solutions (however Delphi provides also the sax-style JSON parser too, give it a try if SAX works for you).


As already mentioned if you want/can adopt an event-driven parser (a.k.a. SAX-style) Delphi has a very nice small framework contained in units System.JSON.Readers.pas and System.JSON.Writers.pas. Give them a look here and here.

There are many 3rd party JSON parser out there. The general advice is always the same: Don’t try solve a non existent problem. So if you have to handle “normal size” JSON or speed is not a concern (batch?), the built-in parser is more than enough, is supported (used also by Embarcadero) and doesn’t add any external dependecies. In many cases this is a very good point in favor of the built-in solution. However, in case you “have the numbers” and you want to try a different JSON parser, you can choose one of the following (not exaustive list):

This is not a complete list. You could find other libraries to handle JSON here.

Writing WEB API with JSON

Creating robust and efficient web APIs is an essential skill for modern programmers, and utilizing JSON (JavaScript Object Notation) as the data interchange format can greatly enhance the effectiveness of these APIs. JSON’s lightweight structure and human-readable syntax make it a perfect fit for transmitting data between servers and clients. Writing web APIs with JSON is a strategic choice that fosters interoperability and enhances the user experience.

Leveraging DelphiMVCFramework, a high-performance framework for building RESTful APIs, JSON’s lightweight and intuitive nature shines. DelphiMVCFramework’s innate JSON support streamlines data serialization and deserialization, seamlessly translating complex data structures into JSON format. This dynamic duo ensures efficient communication between clients and servers, empowering developers to create scalable and responsive APIs. With JSON’s simplicity and DelphiMVCFramework’s power, crafting modern web APIs becomes a harmonious endeavor, driving innovation and interconnectivity in the digital landscape.


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