Injecting current git commit id into Java webapp

Question

We have a git repository which contains source for a few related Java WARs and JARs. It would be nice if the Java code could somehow:

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Answer 1

You can get the last commit SHA with

git rev-parse HEAD

but it's generally a lot more useful to use

git describe

which will give you something that looks like this:

v0.7.0-185-g83e38c7

This works if you have tags - it will tell you how many commits from the last valid tag your current checkout is at plus a partial SHA for that commit, so you can use it to base a checkout off of later. You can use this identifier just like a SHA in most circumstances, but it's much more human readable.

Answer 2

First, you can use ident gitattribute with $Id$ keyword (although it is not probably what you want; it is hash of file contents, and has nothing to do with current project version).

Second, you can do it the way Linux kernel and Git itself do it: in Makefile (in your case: in Ant file) there is rule which replaces some placeholder, usually '@@VERSION@@' (but in case of Perl it is '++VERSION++') by result of GIT-VERSION-GEN, which in turn uses "git describe". But for that to be useful you have to tag your releases (using annotated / signed tags).

Answer 3

If it helps for someone else. I know yours is ANT

For MAVEN build, you could probably use git-commit-id-plugin in your pom.xml file

    <plugin>
        <groupId>pl.project13.maven</groupId>
        <artifactId>git-commit-id-plugin</artifactId>
        <version>2.2.0</version>
        <executions>
            <execution>
                <goals>
                    <goal>revision</goal>
                </goals>
            </execution>
        </executions>
        <configuration>
            <dotGitDirectory>${project.basedir}/.git</dotGitDirectory>
            <generateGitPropertiesFile>true</generateGitPropertiesFile>
            <generateGitPropertiesFilename>${project.build.outputDirectory}/git.properties</generateGitPropertiesFilename>
        </configuration>
    </plugin>

Please go through :
1. http://www.baeldung.com/spring-git-information &
2. https://github.com/ktoso/maven-git-commit-id-plugin for more info.

Answer 4

I wrote an Ant task to get the buildnumber using JGit API (without git command line app), see jgit-buildnumber-ant-task. Then you can store this buildnumber inside MANIFEST.MF file and get it from the classpath on runtime.

Answer 5

I don't know if there are any Ant task for git (I googled a bit without success), anyway Ant can update a properties file with Piotr's option (git rev-parse HEAD) and then in runtime use that properties to get the revision number. This is cleaner and IDE friendly than having Ant generating a .java file.

Answer 6

git rev-parse HEAD will print what you probably want (e.g. id of HEAD commit). You can make ant generate a simple Java class with this id as a static constant.