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Having Problems?

Having Problems?

This page details some steps you can take to try and resolve any problems you may be having with Apache 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.

Ensure that you are actually running the version of Ant that you think you do

Many tools include a version of Ant and some Operating Systems even install it by default now, so you may have a version of Ant installed that you haven't been aware of.

One of the first things to do is to run

ant -version


ant -diagnostics

to be sure. Also, we highly recommend that you run Ant with an empty CLASSPATH. If any other version of Ant can be loaded from the CLASSPATH, many types of errors may happen because of incompatible classes being loaded.

See the FAQ for some examples, but many other problems are a result of an old version of Ant on your system as well.

Read the Manual

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.

Examine Debug Output

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 verbose flag:

ant -verbose


ant -v

This will produce output that starts like the following:

Ant version 1.4.1 compiled on October 11 2001
Buildfile: build.xml
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 -verbose. 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 using redirection.

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 skipping another. 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 <javac> task 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.

Has It Been Fixed?

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, would be to download the sources of ant, see svn.

Gump is building ant every night and using the ant built from the latest source to build a long list of open source projects. However, the version of ant built by gump is not available for download. Even if it were, it would not include most of the optional tasks.

We currently do not have nightly builds including the optional tasks.


If you are convinced that you have identified an unfixed bug, please turn to our document concerning the bug database.