How do I install QJson on a Unix-like system?

QJson requires Qt 4.5+ and cmake. Follow the build instructions: create a build directory, run cmake with your preferred install path, then make and make install. Note that it's archived, so compatibility with modern systems may vary.

QJson vs Qt native JSON: which is better for my project?

For Qt5 or later, always use Qt's native JSON support as it's built-in, actively maintained, and more integrated. QJson is only necessary if you're stuck with legacy Qt3 or Qt4 codebases without JSON capabilities.

How to map JSON data to a QObject using QJson?

Use the QObjectHelper class provided by QJson to convert JSON to QObject properties. The README mentions running tests with ./tests/qobjecthelper/testqobjecthelper for examples, but documentation is minimal due to its archived status.

Is QJson still supported or updated?

No, QJson has been archived since Qt5 introduced built-in JSON handling. There are no active updates, bug fixes, or community support, so it's not suitable for new projects.

Can QJson handle large JSON files efficiently?

While QJson was designed for efficiency in its time, performance might not be optimized for very large or complex JSON files compared to modern libraries, and its archived status means no performance improvements or benchmarking.

Why would I use QJson instead of other JSON libraries for Qt?

Only if you're maintaining legacy Qt3 or Qt4 applications and need a simple, integrated solution that maps directly to Qt's QVariant system. Otherwise, Qt's native JSON or other active libraries offer better support and features.

Open-Awesome

QJson

LGPL-2.1C++

A Qt-based library for mapping JSON data to QVariant objects, now archived as Qt includes native JSON support.

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292 stars145 forks0 contributors

What is QJson?

QJson is a Qt-based library that maps JSON data to QVariant objects, allowing developers to easily convert between JSON and Qt's native data structures. It was created to provide JSON support for Qt3 and Qt4 applications before Qt5 included built-in JSON handling. The project is now archived as its functionality is superseded by Qt's native JSON capabilities.

Target Audience

Qt developers working with Qt3 or Qt4 who need to parse, serialize, or manipulate JSON data within their applications.

Value Proposition

QJson offered a straightforward and integrated solution for JSON processing in Qt environments before native support was available, with features like QObject mapping and a command-line tester for validation.

Overview

QJson is a qt-based library that maps JSON data to QVariant objects.

Use Cases

Best For

Adding JSON support to legacy Qt3 or Qt4 applications
Converting JSON data to QVariant objects for Qt-based projects
Serializing QVariant data structures to JSON format
Mapping JSON objects to QObject-derived classes in Qt
Testing JSON parsing and conversion in Qt environments
Integrating JSON data with Qt's type system before Qt5

Not Ideal For

Modern Qt5 or Qt6 projects with built-in JSON support
Teams requiring active maintenance, bug fixes, or new feature development
Applications needing compatibility with latest JSON standards or Qt advancements
Projects where LGPL licensing is too restrictive for distribution

Pros & Cons

Pros

Seamless Qt Integration

Directly maps JSON arrays to QVariantList and objects to QVariantMap, leveraging Qt's native type system for straightforward data conversion, as highlighted in the README.

QObject Mapping Utilities

Includes QObjectHelper for mapping JSON data to and from QObject-derived classes, simplifying serialization in Qt applications, with dedicated unit tests available.

Built-in Validation Tools

Provides a cmdline_tester for validating JSON parsing and conversion, aiding in debugging with command-line options, as described in the testing section.

Open Source License

Licensed under LGPL v2.1, allowing use in both open-source and proprietary projects with proper attribution, offering flexibility for legacy deployments.

Cons

Obsolete and Archived

The project is archived and no longer maintained, as Qt5 introduced native JSON support, rendering it redundant for modern development and risking unresolved issues.

Limited to Old Qt Versions

Only supports Qt 4.5 or greater, specifically targeting Qt3 and Qt4, making it incompatible with Qt5+ and missing out on newer Qt features and optimizations.

Complex Build Setup

Requires cmake and specific build options (e.g., -DCMAKE_BUILD_TYPE), which can be cumbersome compared to Qt's integrated build systems or modern package managers.

Frequently Asked Questions

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