JSON and XML

Have you ever wondered how is it possible that two different systems can share a document or, in general, share data, when most likely each system is built with a different technology? 

That's the problem JSON and XML solve.

JSON (JavaScript Object Notation) and XML (eXtensible Markup Language) are the two most popular data interchange formats. What does that mean?

A data format is fundamental in integration scenarios. Integration is all about connecting different systems, applications or components where, all of them, have their own language, syntax and format to represent data. Having a standard of representing data allows us to have a common format for all of them and, hence, allows us to exchange data among systems, applications and components.

A little bit of History

XML
Before JSON, XML was widely used for data interchange, configuration files, and document storage due to its flexibility and support for complex data structures. It became the standard for various web technologies, including SOAP (Simple Object Access Protocol) and RSS (Really Simple Syndication).

JSON
As web applications evolved and required faster, more efficient data interchange formats, JSON emerged as a preferred alternative due to its simplicity and better performance characteristics. JSON's lightweight nature made it particularly suitable for web APIs and asynchronous browser-server communication.

When do we need to exchange data?

Basically, each and every scenario of integration needs to adopt a common data format. Here are some common situations:

Web Applications:

• Client-Server Communication: When a web application interacts with a backend server, data interchange is necessary. For instance, when a user submits a form, the data is sent to the server, which processes it and returns a response, often in JSON format.
• AJAX Requests: Modern web applications use AJAX (Asynchronous JavaScript and XML) to fetch data from the server without reloading the page. JSON is commonly used in these requests due to its lightweight nature.

APIs and Web Services:

• RESTful APIs: Many web services and APIs use JSON to format the data being sent and received. This allows different systems to communicate with each other over the web.
• SOAP APIs: While SOAP traditionally uses XML, many modern implementations support JSON as well, providing flexibility in data interchange.

Microservices Architecture:

• In a microservices architecture, different services often need to communicate with each other. JSON is commonly used for this inter-service communication due to its simplicity and ease of integration.

Mobile Applications:

• Mobile apps frequently communicate with backend servers to fetch or send data. JSON is often used in this communication to ensure efficient and lightweight data interchange, which is crucial for performance on mobile networks.

Data Storage and Configuration:

• JSON is also used for storing configuration settings and lightweight data storage, especially in NoSQL databases like MongoDB.

Data Exchange Between Different Programming Languages:

• JSON's language independence makes it ideal for exchanging data between applications written in different programming languages.

Inter-Organizational Data Sharing:

• Organizations often need to share data with partners, clients, or regulatory bodies. JSON provides a standardized format that can be easily understood and processed by different systems.

Cloud Services:

• Many cloud services use JSON for data interchange, especially when dealing with APIs for storage, computation, or other services.

Key Differences between XML and JSON

Syntax

• JSON:
• Lightweight and more concise.
• Uses key-value pairs for data representation.
• Data is represented in a hierarchical structure using arrays and objects.
• Syntax is similar to JavaScript object literals.

• XML:
• More verbose and heavier in terms of data representation.
• Uses tags to define elements and attributes to provide additional information.
• Data is represented in a tree structure with a clear start and end tags.
• Requires closing tags for every element and can include attributes within elements.

Readability

• JSON:
• More human-readable due to its concise and straightforward syntax.
• Easier to read and write manually.
• XML:
• More verbose and can become complex with nested elements and attributes.
• Tags can make it harder to read, especially for deeply nested structures.

Parsing and Generation

• JSON:
• Easy to parse using built-in functions in most programming languages.
• Directly convertible to native data structures in languages like JavaScript, Python, etc.
• Typically faster to parse due to its lightweight nature.
• XML:
• Requires a parser to process and extract data.
• Can be more complex to handle due to namespaces, attributes, and the need to navigate a hierarchical structure.
• Parsing can be slower compared to JSON due to its verbosity.

Data Types

• JSON:
• Supports basic data types like strings, numbers, arrays, objects, booleans, and null.
• Data types are directly mapped to corresponding data structures in most programming languages.
• XML:
• Does not have built-in data types; all data is treated as text.
• Requires additional processing or schema definitions (like XSD) to enforce data types.

Summary

XML and JSON are the most popular formats to interchange data among systems, applications and components. They play a crucial role in integration.

XML was developed before JSON, however due to its simplicity, ease of use and performance JSON has got much better adoption,  becoming the de facto format when it comes to web applications and APIs.