[fedora-java] Re: Java on Fedora faq

[John M. Gabriele]

--- Robin Green <greenrd at presidium.org> wrote:

> On Tue, 26 Jul 2005 08:02:12 -0700, John M. Gabriele wrote:
> 
> > It's starting to come along. :)
> > 
> > http://www.simisen.com/jmg/pmwiki/pmwiki.php?n=Main.JavaOnFedora
> 
> Here are a voluminous amount of suggested changes and additions!

Just who *are* you Mr. Green? :) Thanks for the suggestions!


> >Sun's Java and GNU Java should be able to coexist on the same system, but
> >I wouldn't know how to get that configuration working.
> 
> Sun's Java and GCJ are, of course, able to coexist on the same system. Follow
> this simple five step guide to get the recommend setup:
> 
> 1. Download a Sun JDK (not a JRE!) from
> http://java.sun.com/j2se/1.5.0/download.jsp - and make sure you choose the
> "Linux RPM in self-extracting file" option.
> 
> 2. Make the file you've just downloaded executable by typing
> chmod +x [insert filename here]
> 
> 3. Execute it by typing ./[insert filename here] This will extract and then
> install the RPM for you.
> 
> 4. Download the binary package java-1.5.0-sun-compat-1.5.0.04-1jpp from
> jpackage.org. (The version number may be different by the time you read
> this.)
> You will find java-1.5.0-sun-compat near the bottom of the long
> list of packages on the left side of the page - click on that and then click
> on the first icon in the B column (on jpackage.org, B is for binary package,
> H is for project homepage and S is for source package.)
> 
> 5. Install it with rpm -ivh java-1.5.0-sun-compat-1.5.0.04-1jpp*.rpm
> 
> Optionally, you can now make the Sun JDK the default, by typing
> 
> alternatives --configure java
> 
> This will only affect "java" and a few other commands. To make the Sun Java
> compiler and JDK development tools the default as well, you also need to do:
> 
> alternatives --configure javac
> 
> If you wish to use a different JDK to the default one, without changing
> your current default, you will find each JDK in its own directory under
> /usr/lib/jvm - along with some shortcut links like "java-gcj" to save typing.
> 
> Note that JPackage (at runtime), JPackage (when package building), and many
> Java applications, all have their own separate systems for setting "default"
> virtual machines. So just because you set the system default with the
> alternatives command, that does not mean it will affect everything.

Robin -- thank you for the excellent instructions. However, my
little hole-in-the-wall faq is aimed squarely at helping new Fedora
users get started using the GNU Java implementation that comes
with FC. As such, I've changed the link from JavaOnFedora to
GNUJavaOnFedora:
http://www.simisen.com/jmg/pmwiki/pmwiki.php?n=Main.GNUJavaOnFedora

But your instructions are too good to go to waste! You might consider
sending them off in a note to the fellow who runs the fedorafaq:
http://www.fedorafaq.org/#java since there's some similar (but
possibly improvable) instructions there for almost the same thing.

Similarly, there are instructions here also
http://stanton-finley.net/fedora_core_4_installation_notes.html#Java
that you may be able to help fine-tune.


> > Can I do Java GUI development on Fedora without Swing or AWT?
> >
> > Certainly. You've even probably already got the necessary packages
> installed. See Java-Gnome.
> 
> Certainly. You've even probably already got the necessary packages installed.
> The two
> main options are SWT (the cross-platform toolkit that uses native libraries
> like GTK to render
> stuff) and Java-Gnome.
> 
> If you want to develop cross-platform applications, your best choice
> is probably SWT, which comes in the libswt3-gtk2 package, and is supported by
> Eclipse.
> 
> Eclipse has a visual editor component like other IDEs, called VE (Visual
> Editor), but it isn't shipped in
> Fedora yet. You can download it from eclipse.org and unzip it (as root) into
> /usr/share/eclipse
> - the eclipse updating mechanism doesn't work, so it's best to install it
> manually like that.
> It's not necessary to install VE to develop SWT applications - VE just
> provides a visual, 
> "drag-and-drop" way of developing SWT, Swing and AWT applications and
> components.

By now I'm sure you're noticing my leaning toward using copylefted
software when possible. As far as creating your own software, I regularly
suggest to others that if your software is to depend on other pieces to
run, it's preferred that those pieces be GPL'd or LGPL'd.

But, again, you've given some great suggestions, so I've tried to
incorporate them while still maintaining the flavor of the document.

> >Where do I file bugs on Java software in Fedora?
> >
> >There isn't a Java-software-specific bug-reporting page. Please use:
> https://bugzilla.redhat.com/bugzilla/ . Just be sure to search >first, to see
> if your bug is already listed. 
> 
> Consider carefully the appropriate bug database to use. Firstly, can you
> determine or estimate[1]
> (for example by running the software on a Sun JDK) if it is a bug in the Java
> software
> you are using, or it is a bug in gcj/gij/libgcj? If the former, consider if
> it might be
> appropriate to report the bug to that project itself, rather than reporting
> it on the Fedora bug database.
> If the latter, it is appropriate to post the bug to the fedora bugzilla
> (either under the specific package,
> or under "gcc" if you can identify a specific compiler or interpreter bug).
> gcc also has its own bug database
> at gcc.gnu.org, but Fedora gcc is hardly modified from mainline gcc in terms
> of the Java stuff, and
> many of the same people read both databases, so it's not the end of the world
> if (improbably) you post
> a Fedora-specific bug to the gcc database by mistake.

Thanks. :)

> > How do I create a Java project in Eclipse on Fedora?
> 
> Easy. Just start eclipse by typing "eclipse" (that was hard, wasn't it!) (You
> can specify a particular virtual
> machine to use by typing eclipse -vm /usr/lib/jvm/jre-gcj/bin/java .) Then go
> to the File menu and choose
> New -> Project. Type your project name, choose the options, and click Next
> (for more options) or Finish.
> Notice that you can import existing source code at this point.
> 
> Eclipse may now ask you whether you want to switch to the Java Perspective.
> If so, say Yes!
> 
> Then create a New Class. If you're starting from nothing, you probably want
> to ask eclipse to create a
> "public static void main (String args [])" method for you at this point
> (Eclipse is really good at
> taking of drudgery like that). Now you can go ahead are start typing!
> 
> If you develop GUIs and you prefer working in a more visual style, see above
> for details about Eclipse's
> VE plugin.
> 
> Some quick tips: You can configure project-specific preferences (like which
> JDK to use, code style conventions,
> warnings to supress, etc.) by right-clicking on the project in the project
> browser on the left and choosing
> Properties. You can navigate to the declarations of fields or methods in your
> code by highlighting them
> and pressing F2, or by using the code structure browser on the right.
> When you get a compiler error, highlight the code that Eclipse is complaining
> about and press CTRL+1 - eclipse
> will usually be able to offer you some "quick fix" suggestions as to how to
> fix it - and it will not only
> suggest them but actually implement them for you. Very handy!
> 
> When you're comfortable with the basics of Eclipse, try right-clicking on
> code or variables and exploring
> the many refactoring options that are on offer. Refactoring is essentially
> like the Quick Fix system, but
> user-initiated.
> 
> Caveats: Unfortunately, a couple of things do not work well when running
> eclipse on libgcj on Fedora Core 4.
> Firstly, some users have reported hangs with large CVS checkouts (although
> this may only apply to
> bleeding-edge releases from the Fedora Development package repository).
> Secondly, debugging doesn't
> work at all with a libgcj virtual machine, because it's not implemented in
> libgcj yet - although work on
> that is underway.

Thank you! Had no idea about that debugging caveat! You know though,
reading your short howto reminds me how many other good ones are
already out there for Eclipse (not to mention the Eclipse docs, which
seem fairly complete).

I think I'm going to opt for brevity, and simply try and point
out the Fedora-specific Eclipse tips you'll need to know to get
started quickly.

> > How do I use Tomcat?
> 
> Very briefly: "service tomcat4 start" or "service tomcat5 start" will start
> tomcat.
> (Can you guess how to stop it?) Then use "rpm -ql tomcat5|less" to explore
> the directory structure of Tomcat
> on Fedora. The main thing you need to know is that you put your webapps under
> /var/lib/tomcat{4,5}/webapps.

I'm working through that at the moment (though rapidly running out of time
tonight), and your tips should come in helpful. :) Hmm... perhaps my tomcat is
configured incorrectly, because I don't have a /var/lib/tomcat5 directory... I
*do* have a /usr/share/eclipse/plugins/org.eclipse.tomcat_4.1.30.1/webapps
though...

Thanks again,
---J



		
____________________________________________________
Start your day with Yahoo! - make it your home page 
http://www.yahoo.com/r/hs