java-gnome 4.1.3, released 4 May 2013
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README

This is the java-gnome language bindings project. We endeavour to provide a high quality library you can use to write GTK and GNOME programs. The underlying APIs are elegantly transformed into Java and carefully documented so that anyone new to Linux or Open Source can rapidly be on their way to creating fabulous applications.

This README file is devoted to helping you get started building the bindings themselves.

Building java-gnome

For the impatient:

$ tar xJf java-gnome-4.1.3.tar.xz
$ cd java-gnome-4.1.3
$ ./configure
$ make

But there’s a bunch of stuff you probably want to know, so read on!

1. Get the source code

From a release tarball

You can download the latest java-gnome release from the GNOME FTP server at:
http://ftp.gnome.org/pub/gnome/sources/java-gnome/4.1/

Once you’ve downloaded the latest source tarball:

$ tar xjf java-gnome-4.1.3.tzr.xz
$ cd java-gnome-4.1.3

And go on to step 2 for details about options you can pass to the configuration command.

Or checkout the source

If you want a newer version of the code than the tarball you might have, you can always check it out over the net. We use Bazaar (bzr), an advanced third-generation Distributed Version [or Revision] Control System, to manage our source code.

Getting a checkout is easy:

$ cd ~/src/
$ mkdir java-gnome/
$ git clone git://github.com/afcowie/java-gnome.git mainline
$ cd mainline/
$ less README.markdown

2. Run ./configure

The top level directory contains a custom ./configure which detects your Operating System variant, sets defaults accordingly, verifies the location of prerequisites (the various .jar files), and finally chooses a Java bytecode compiler and Java Virtual Machine runtime environment. The configuration output is a Makefile fragment which is written to .config and subsequently included by the top level Makefile.

So run it already:

$ ./configure

Background

The steps necessary to configure and build a Java project are quite different than those needed to construct a program written in a more traditional language. Unlike C, for example, there is no need to do substitution across the codebase nor to worry about conditional compilation; #ifdef is not something we do in Java. This is in no small part because the Java class libraries and the language itself have been remarkably stable. To build and run a Java program, however, three things are necessary:

That’s it! From there, often a single compiler invocation will take care of building an entire program, but these preconditions must be satisfied before compiling is possible. (Incidentally, tools like Ant are no help with any of this — it just takes care of the build part; and don’t even think about suggesting the GNU autotools — they are a complex, arcane, and bloated nightmare that don’t address with the Java specific challenges at all).

At the moment, we use Andrew Cowie’s “Equivalence” build system, which is composed of a straight-forward (if somewhat overweight) Perl program along with a simple Makefile which together carry out the task of configuring and building the library. Right now, Gentoo Linux, Debian Linux, Fedora Core Linux, and Solaris Unix should be detected properly and result in working configurations. If you are running a different operating system or distribution, please contact us and we’ll add it — it’s just a matter of identifying the location of a few things. Better yet, look in the configure Perl script — the places where OS is switched are obvious, and just add what you need to add, and send us a patch.

Meanwhile…

Customizing build options

You can override the choices configure makes by listing parameters on the command line, like this:

$ ./configure compiler=ecj runtime=jamvm

This facilitates easily switching between runtimes and compilers for testing. At the moment, the available selections are:

The whole point of the Equivalence’s configure script is to figure things out for you, but if it can’t quite figure out where Java is, you can override it by specifying an alternate location to find a JDK using either of the following:

Examples:

$ ./configure
$ ./configure jdk=/opt/sun-jdk
$ ./configure jamvm=/home/joe/custom/bin/jamvm runtime=jamvm

Your configuration is persistent across builds in that checkout, ie, make clean won’t force you to reconfigure (though make distclean will). The configure script runs very quickly, so it’s no big deal to switch settings by re-running it.

Dependencies

The java-gnome library depends on the GNOME desktop and is intended for people wishing to do tight integration with it. In particular, this version of java-gnome depends on:

3. Build

Once you’ve configured, compiling java-gnome is as simple as running Make:

$ make

If you’re having trouble with something as Make runs and need to debug it, you can try:

$ V=1 make

This will show you the actual commands being executed (ie, Make’s normal behaviour, which we override for appearances sake and because otherwise the signal to noise ratio is terrible and you never see warnings). If you’re still stumped, you might try having a look at .config, which is where all the Make variables come from.

The build products end up in tmp/:

tmp/gtk-4.1.jar
tmp/libgtkjni-4.1.3.so

That’s actually enough to go on — if you’re using an IDE like Eclipse you can just tell it about the .jar and then jump right to “Using the Bindings”. Or you can install java-gnome somewhere. Doesn’t matter, really.

4. Install

java-gnome 4.1 has the standard make install behaviour, and the equally standard prefix option to ./configure.

Installing locally

Someone installing it locally (to your home directory, say) might do:

$ ./configure prefix=/home/bloggins
$ make install

and you would end up with:

~/share/java/gtk-4.1.jar
~/share/java/gtk.jar
~/lib/libgtkjni-4.1.3.so

The default is to send it off to /usr/local as you’d expect.

Using make install is compulsory if you intend to use java-gnome from anywhere other than “in-place” from the temporary location where it was built.

Installing to system (for people packaging the library for their distro)

The install target understands the DESTDIR variable used by packagers to install to a specified prefix within a temporary directory. Someone writing an .ebuild to create a package for java-gnome on a Gentoo system would probably end up seeing the following commands being run by Portage, for example:

...

./configure prefix=/usr
make

...

make DESTDIR=/var/tmp/portage/java-gnome-4.1.3-r2/image install

...

With a prefix of /usr you will end up with:

/usr/share/java/gtk-4.1.jar
/usr/share/java/gtk.jar
/usr/lib/libgtkjni-4.1.3.so

If you have distro policy issues to deal with, then pass jardir and/or libdir overrides to configure.

Using the bindings

Running the “demo”

There are a few tiny and trivial example programs in the doc/examples/ directory of the bindings. If you would like to see one, you could compile and run it by hand, doing something like:

$ javac -classpath tmp/gtk-4.1.jar -d tmp/tests doc/examples/button/ExamplePressMe.java
$ java -classpath tmp/gtk-4.1.jar:tmp/tests button.ExamplePressMe

This shows you how you can reference and use the library after it is built by make into tmp/.

Of course, that was way too much typing. Instead, just do this:

$ make demo

:). As usual, use V=1 to see what it is actually doing.

Running your own programs

java-gnome has a native component that links tightly against various GNOME libraries (after all, the whole point is to use the real GTK, not some pseudo look alike pathetic attempt of a widget toolkit), but we take care of locating it and loading it for you. So all you need to do to run an application is:

$ java -client -ea                                   \
    -classpath /home/bloggins/share/java/gtk-4.1.jar \
    com.example.ComeOnBabyLightMyFire

Oh, the joys of running Java programs by hand.

Status

java-gnome is now a solid foundation that has been used to develop non-trivial applications. The architecture and internal design has been well proved, and the coverage level (relative to the full breadth of the underlying libraries) is reaching maturity.

Get Involved

If you would like to get involved yourself as an individual, we would welcome your contribution. See HACKING. If you are working on an application, want to learn more, or are just curious, join us online in #java-gnome on irc.gimp.net.

Happy coding!

AfC

--
Andrew Frederick Cowie
Managing Director,
Operational Dynamics,
a Change Management consultancy…

Maintainer,
java-gnome,
opening GTK and GNOME to Java programmers!

Last modified 22 Feb 13

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