Google Web Toolkit vs J2ObjC

Google Web Toolkit (GWT) is a free, open-source Java framework for building AJAX web applications. Its compiler converts Java applications into JavaScript and HTML for browser use, and the SDK includes the core libraries and compiler. Deferred binding generates browser-specific code at compile time, while the compiler can create separate application versions for different browsers and languages. Applications can communicate asynchronously with servers through GWT RPC or JSON. An Eclipse plugin provides IDE support and an option to install the SDK. The developer guide covers deployment to Google App Engine, JUnit unit testing and Emma code coverage; documentation also includes SafeHtml guidance for XSS prevention and GWT RPC XSRF protection. GWT is licensed under Apache 2.0 for non-commercial, commercial and enterprise applications. Version 2.13.1 is listed for Windows, Mac OS X and Linux. Development mode and the compiler periodically send a timestamp ID and product version to Google; Google says it does not log cookies or personal information. The webAppCreator utility has been deprecated since version 2.11.0.

J2ObjC is Google’s free, open-source command-line tool for translating Java source code into Objective-C for iOS. It is designed for sharing non-UI application logic and data models across web, Android, and iOS projects. Supported Java features include exceptions, inner and anonymous classes, generics, threads, and reflection, and the tool can translate and execute JUnit tests. The distribution contains static libraries for Guava, JUnit, Mockito, Protocol Buffers, and other Java or Android utility libraries. J2ObjC does not provide a platform-independent UI toolkit; iOS interfaces use Objective-C, Objective-C++, or Swift with Apple’s iOS SDK. Developers need source code they own or are licensed to use because Android binaries cannot be converted. Requirements include a Mac workstation, macOS 15 or higher, Xcode 16 or higher, and JDK 21 or higher. The j2objcc script wraps clang and uses the iOS SDK, while Xcode projects need J2ObjC linker settings. Objective-C reference counting leaves memory management to developers.