Qt Jambi
Warning: Qt Jambi works only with Qt4. The project seems to be dead.
This is a community maintained project ('qtjambi-community') that provides Java language bindings to the Qt APIs. The bindings are generated by inspection of the C++ header files of the Qt implementation then emitting code to provide the necessary JNI (Java Native Interface) and .java files to provide linkage to Java. An application programmer using Qt Jambi would simply add the.jar files to their Java project to be able to develop and deploy their application.
The bindings implement such things as signal/slot mechanics for Java and cross-thread marshaling of an event driven programming model. Indeed the API presented to the Java programmer is very similar to the C++ APIs so your knowledge of C++ can largely be transferred to Java. These alternative programming models maybe considered a new and refreshing choice for application developers looking for an alternative to the strict static type programming patterns employed by other Java UI toolkits. Qt Jambi makes use of Java reflection and can integrate with the QMetaObject system (that provides similar reflection mechanism to C+). However it does not preclude the use of any Java patterns from your application design Qt Jambi provides additional ways to program java.
There is much overlap with some Qt modules with already existing Java APIs and 3rd party libraries. Qt Jambi does not inhibit or restrict the implementation of a feature you choose to use. Some of the strengths of Qt to Java are in the cross-platform UI toolkit, the programming model, UI scripting support, embedded web browser support.
The qtjambi-community source project integrates with all Qt versions between 4.5 and 4.8, this includes, 4.6 and 4.7. Work on Qt5 is planned but not until the release of 5.1 where Qt on the desktop will get attention. One aspect of the project is that due to the generation technique bug fixes applied to the project can still be used with all supported Qt versions, there is no need to back-port such fixes. Simply rebuild the project against the version of Qt you wish to use.
Another feature of the project is that it is possible to reuse your custom C++ QWidget's and other QPlugins with Qt Jambi. If your objects expose QMetaObject they may simply work as the java bindings are able to invoke and integrate with QMetaObject. Alternatively you can use the generator (provided in the Qt Jambi project) to expose Java API bindings for your custom plugins, an example of this is provided in the project sources. This allows you to combine the benefit of C++ performance in areas where it is needed with the rapid application development enjoyed by Java developers.
The Community website for Qt Jambi can be found at Qt Jambi Community's website.
The Community bug tracker: Qt Jambi Community bug tracker
The Community patch submission: Qt Jambi Community gerrit
Qt Jambi past
Before March 2009 the project ('qt-jambi') was maintained and released by Trolltech, their latest release was Qt Jambi 4.5.2_01 based on a port of Qt 4.5.2. This is last version by the Qt team (based at Trolltech). When Nokia purchased Trolltech the Qt Jambi project was not put into the future road map so the work was spun off into the open source project. The source code project that is called 'qt-jambi' is from this pre March 2009 era and does not support any version of Qt 4.7 or later.
Binaries
Repository
http://qt.gitorious.org/qt-jambi/qtjambi-community this source tree is actively being developed
http://qt.gitorious.org/qt-jambi/qt-jambi this source tree has not been maintained since March 2009
Ubuntu (PPA from Launchpad)
It is best to read download and install instructions in PPA description at:
This tries to cover all recent Ubuntu releases and LTS releases that are compatible with Qt Jambi project.
OBS (OpenSuSE build system, including Fedora/Red Hat/CentOS and SLS/OpenSuSE)
See OBS wiki and documentation for how to add a custom repository to your distribution. Then you can download, update and install via your Linux package manager.
See also
This page describes the Java bindings. There is also QtScript which is the JavaScript bindings. Similar sounding technologies, but very different :)