This page details some steps you can take to try and resolve any problems you may be having with Ant. If you find you can't resolve the problem, then this page will help you collect some of the relevant information to provide in a bug report. This information will help the Ant developers understand and resolve the problem. Of course, not all the steps here will make sense for every problem you may encounter - these are just some suggestions to point you in the right direction.
The first step to take when you have a problem with Ant is to read the manual entry for the task or concept that is giving you trouble. In particular, check the meaning of a task's attributes and nested elements. Perhaps an attribute is available that would provide the behavior you require. If you have problems with the manual itself, you can submit a documentation bug report (see below) to help us improve the Ant documentation.
If you're still having a problem, the next step is to try and
gather additional information about what Ant is doing.
Try running Ant with the
This will produce output that starts like the following:
Ant version 1.4.1 compiled on October 11 2001
Detected Java version: 1.3 in: D:\usr\local\java\jdk13\jre
Detected OS: Windows NT
parsing buildfile D:\ant\build.xml with URI = file:D:/ant/build.xml
Project base dir set to: D:\ant
[property] Loading Environment env.
[property] Loading D:\ant\conf.properties
Build sequence for target 'debug' is [debug]
Complete build sequence is [debug, gensrc, compile, jar, test]
. . .
You should be able to see from the trace more about what Ant
is doing and why it's taking a particular course of action.
If you need even more information, you can use the
-debug flag rather than
This will generally produce so much
output that you may want to save the output to a file and
analyze it in an editor. You can save the output using the
-logfile <filename> flag, or
Once you have all this debug information, how can you use it
to solve your problem? That will depend on the task in question
and the nature of your problem. Each task logs different aspects
of its operation, but it should give you an idea of what is going
on. For example, the
<javac> task logs the
reasons why it
chooses to compile particular class files and not others, along
with which compiler it is using and the arguments it will pass
to that compiler. The following partial trace shows why
<javac> is adding one class file but
This is followed by which compiler it will be using, the
arguments that will get passed to the compiler,
and a list of all the class files to be compiled.
[javac] Test.java omitted as D:\classes\Test.class is up to date.
[javac] Unset.java added as D:\classes\Unset.class is outdated.
[javac] Compiling 1 source file to D:\classes
[javac] Using classic compiler
[javac] Compilation args: -d D:\classes -classpath D:\classes;
D:\jdk118\classes.zip; -sourcepath D:\src\java -g:none
[javac] File to be compiled:
In many cases, Ant tasks are wrappers around OS commands or
other Java classes. In debug mode, many of these tasks will
print out the equivalent command line, as the
output does. If you are having a problem, it is often useful to
run the command directly from the command line, in the same way
Ant is running it, and see if the problem occurs from there
as well. The problem may be in the command that is being run,
or it may be in the way the Ant task is running the command.
You can also see the effect of changing attribute values on the
generated command line. This can help you to understand whether
you are using the correct attributes and values.
After examining the debug output, if you still believe that the problem you are having is caused by Ant, chances are that someone else may have already encountered this problem, and perhaps it has been fixed. The next step, therefore, may be to try a nightly build of Ant to see if the problem has been fixed. Nightly builds for Ant are available from the Ant web site. While Ant nightly builds are typically quite stable and are used by Gump to build many other Jakarta projects, these builds should nonetheless be treated as experimental. Note that nightly builds do not build many of the optional tasks the come with Ant. A snapshot of these optional tasks is occasionally uploaded to the nightly download area. However, even this snapshot does not contain every optional task.
If the current nightly build doesn't resolve your problem, it is
possible that someone else has reported the issue. It is time to
look at the
Apache Bug Database. This system is easy to use, and it will
let you search the
currently open and resolved bugs to see if your problem has
already been reported. If your problem has been reported, you can
see whether any of the developers have commented, suggesting
workarounds, or the reason for the bug, etc. Or you may have
information to add (see about creating and modifying bug reports
below), in which case, go right ahead and add the information.
If you don't have any additional information, you may just want
to vote for this bug, and perhaps
add yourself to the
CC list to follow the progress
of this bug.
By this time, you may have decided that there is an unreported
bug in Ant. You have a few choices at this point. You can send
an email to the
user mailing list
to see if
others have encountered your issue and find out how they may
have worked around it. If after some discussion, you feel it
is time to create
a bug report, this is a simple operation in the bug database.
Please try to provide as much information as possible in order
to assist the developers in resolving the bug. Please try to enter
correct values for the various inputs when creating the bug, such
as which version of Ant you are running, and on which platform,
etc. Once the bug is created, you can also add attachments to
the bug report.
What information should you include in your bug report? The easiest bugs to fix are those that are most easily reproducible, so it is really helpful if you can produce a small test case that exhibits the problem. In this case, you would attach the build file and any other files necessary to reproduce the problem, probably packed together in an archive. If you can't produce a test case, you should try to include a snippet from your build file and the relevant sections from the verbose or debug output from Ant. Try to include the header information where Ant states the version, the OS and VM information, etc. As debug output is likely to be very large, it's best to remove any output that is not relevant. Once the bug is entered into the bug database, you will be kept informed by email about progress on the bug. If you receive email asking for further information, please try to respond, as it will aid in the resolution of your bug.
Sometimes, you may find that Ant just doesn't do what you need it to. It isn't a bug, as such, since Ant is working the way it is supposed to work. Perhaps it is some additional functionality for a task that hasn't been thought of yet, or maybe a completely new task. For these situations, you will want to raise an enhancement request. Enhancement requests are managed using the same Apache Bug Database described above. These are just a different type of bug report. If you look in the bug database, you will see that one of the severity settings for a bug is "Enhancement". Just fill the bug report in, set the severity of the bug to "Enhancement", and state in the description how you would like to have Ant enhanced. Again, you should first check whether there are any existing enhancment requests that cover your needs. If so, just add your vote to these.
If you aren't satisfied with just filing a bug report, you can
try to find the cause of the problem and provide a fix yourself.
The best way to do that is by working with the latest code from CVS.
Alternatively, you can work with the source code available from the
source distributions. If you
are going to tackle the problem at this level, you may want to
discuss some details first on the
mailing list. Once you have a fix for the problem, you may submit
the fix as a patch to either the
list, or enter the bug database as described above and attach the
patch to the bug report. Using the bug database has the advantage
of being able to track the progress of your patch.
If you have a patch to submit and are sending it to the
dev mailing list,
to your message subject. Please include any relevant bug numbers.
Patch files should be created with the
option of the
cvs diff command. For
diff -u Javac.java.orig Javac.java > javac.diffs
or, if you have source from CVS:
cvs diff -u Javac.java > javac.diffs
Note: You should give your patch files meaningful names. This makes it easier for developers who need to apply a number of different patch files.