Integrating Subversion Into Your Ant Build

Author: Jeremy Whitlock
Laste edited: October 13th, 2006
Summary: This article will provide example business use-cases to explain why you may want to use Subversion in your Ant build process and show you how to integrate Subversion into your Ant build process.

Introduction

I have been using Subversion and Ant for a number of years now. When I was working for a previous employer, we had a few business needs where we needed to interact with Subversion or get information from Subversion as part of our build cycle. Since our build cycle was used for release management and continuous integration, there were a number of places where we needed this information. In the beginning, there was no known way to do this so we wrote our own scripts to call the Subversion command line client and parse the output. Eventually, I stubmled upon SVNAnt which made integration Subversion into our Ant build process much easier. So before we get into examples and real-world scenarios that would merit integration Subversion into your Ant build cycle, lets find out what SVNAnt is, what it provides and how to install it.

SVNAnt Use Cases

SVNAnt is just a vessel to being able to get Subversion information and to perform Subversion commands during your Ant build cycle. The examples below are use cases for using Subversion within your Ant build file that I have experienced during previous employment and in my open source development.

Continuous Integration

Continuous Integration (CI) is a multi-step process that usually involved building your application from the latest and greatest, performing some tests, documenting the results and then alerting your team of the outcome. The key part of that sentence for this article is build. In many CI processes, your build tooling is responsible for facilitating the CI steps listed above. Without diving too deep into CI, here are the steps that usually occur during CI:

1. Checkout the latest sources
2. Compile the main sources
3. Compile the test sources
4. Run your tests
5. Report on your test results
6. Report on any other things like code coverage
7. Tag the integration build
8. Publish build artifacts
9. Cleanup

Now I understand that these steps may differ and are probably very minimal but that isn't the point. The point is to look at steps one, six and seven. These three CI steps are all places where you will need to interact with Subversion to facilitate the CI step properly. With SVNAnt, these steps are performed with ease. Without SVNAnt, you usually have to either write your own Ant tasks or have Ant call some external application and parse the data for use during the CI process. Lets look at how Subversion could be used as part of the above CI process:

1. Checkout the code (No other way to do this without Subversion interaction)
2. Get repository information and set to Ant properties for use during documentation creation and artifact naming
3. Create a tag of the successful build with a name understandable via visual examination
4. Possibly commit some of the build artifacts
5. Might also want to set a property on some of the Subversion files/directories based on project needs

Continuous Integration is a perfect example as to why you would need to interact with Subversion during your Ant build cycle. Without being able to interact with Subversion, you might have difficulty creating a tag with your revision number in the tag name, which is usually done to create a tag that can be fully understood from ad-hoc examination. What about publishing your web application to your application server with a name that can be identified by visual examination of the war name? Yet another reason that Subversion interaction via SVNAnt makes your CI process more possible.

Release Management

Release Management is another place where Subversion interaction during the Ant build cycle was required in my past. At one of my previous employers, we "cut a release" via Ant. As part of this release, we built release documentation, tagged our binaries with pertinent revision information from Subversion and we even built release reports based on Subversion properties and log information. Another useful Release Management step that required Subversion interaction was to set a property on the release tag with release information. None of this is possible within your Ant build cycle without Subversion interaction.

There are many other ways that SVNAnt, as part of your Ant build cycle, provides useful, and in many times necessary, access to Subversion. These are just two most common use cases that I've ran into in many projects.

SVNAnt

SVNAnt is an Ant task allowing you to interact with Subversion within the convenience of your Ant build script. No more writing custom scripts to get the revision of your repository to tag your release jars. Nor do you have to make command line calls to checkout your latest and greatest as part of your continuous integration process. With SVNAnt, you have the familiarity of the Ant syntax and the flexibility you need for interacting with Subversion.

Features

SVNAnt is a full-featured Subversion client capable of using the native Java bindings or command-line wrappering depending on which is available. Beyond how it works, SVNAnt allows you to do all svn subcommands but the following:

blame	cleanup	help	list
lock	log	merge	propedit
proplist	resolved	unlocked

If the svn subcommand is not listed here, you can use it in your Ant build file. Before we continue start using SVNAnt, we have to install it and configure Ant to use it.

Installation

Now that we know what SVNAnt is and what its features are, lets install SVNAnt so that you can begin to use SVNAnt to access Subversion within your Ant build cycle.

Step 1. (Download, Compile and Extract)
This step will download, compile, and "install" the latest version of SVNAnt.
1.1 Using Subversion, checkout the SVNAnt project located here: http://subclipse.tigris.org/svn/subclipse/trunk/svnant
1.2 From the command line, while inside of the location where you checked out SVNAnt to, run "ant makeDistrib"
1.3 Extract the .zip file created in the build directory of your SVNAnt source to a location of your choosing

Step 2. (Modify your build.xml)
The next step is to tell Ant how to find your SVNAnt task by adding the following to your build.xml file:

That should be it. I know that it appears to be too good to be true so lets verify this.

Step 3. (Verify installation)
Building upon Step 2, lets create a new ant task that will use the wcVersion feature of SVNAnt to get some information about your repository from a local working copy:

(Note: In the event that you need to pass credentials to Subversion, look here.)

The output should be something similar to this:

$ ant testSVNAnt

Buildfile: build.xml

testSVNAnt:
      [svn] <WcVersion> started ...
      [svn]  finished.
     [echo] Subversion repository url: http://svn.apache.org/repos/asf/incubator/openejb/trunk

BUILD SUCCESSFUL
Total time: 43 seconds

Pat yourself on the back. You have successfully installed SVNAnt and you are ready to implement Subversion into your Ant build cycle. Instead of us going through each available feature for SVNAnt, please view the SVNAnt Documentation. Now lets talk about why you may want to use SVNAnt to allow for Subversion interaction inside of your Ant build cycle.

Summary

This concludes our article on integrating Subversion into your Ant build cycle.  We have discussed two use cases for using Subversion in your Ant build cycle.  We have even installed SVNAnt and verified it works.  The rest is up to you.  Next steps should be to review the SVNAnt documentation referenced in the Resources section and build upon what you've learned today.

I hope this article brings SVNAnt to those of you using Ant but doing Subversion interaction the hard way. For those of you already using SVNAnt, I hope that this article backs up your usage and possibly gives you a few ideas for SVNAnt use in the future.

Resources

The following are resources used during this article:

Resource	Description
Article with Source and SVNAnt binary	Single download with article HTML, sample Ant build.xml and an SVNAnt binary built from the trunk. Download, extract and run
Ant	Multi-platform and multi-language build tool
Subversion	Subversion version control system
SVNAnt	Subversion Ant task
SVNAnt Documentation	SVNAnt documentation complete with installation and usage