Maven buildtime and version creation

When you are building a brand new application, it is usually the time, to challenge the old principles and to conserve the good ones while replacing the rest.

My latest challenge was ... providing visible time of build and version of web application build with Maven. If you are now thinking "bah, that is just easy", you are right, because it is. But my path towards the solution presented in this post was not as easy and straightforward as I would have imagined, so I am presenting one hopefully simple instruction how to do it.

I was deciding whether to put the build time and application version into the MANIFEST.MF file or to use application's  properties file. I have chose to use a properties file because one was already present in the application, thus meaning to me considerably less code needed to write.

Main principle

I am going to use maven's build-in properties along with a properties file, which is going to be filtered. This process will fill in the informations I want (i.e. build time and project version).

There are basically three things you need to do in order to get application's version and build time into a property file.
  1. Create / modify template property file,
  2. add timestamp properties into pom.xml file,
  3. add filtering record into the build section inside the same pom.xml.

Property file

My properties file is called omega.properties, but that is entirely up to you, because the entire directory is filtered (in my example, you could just filter the one file).
The content looks like this:
version=${project.version}
buildtime=${my.timestamp}

Pom.xml

And this is how pom.xml looks like. The head was deprived of artifactId, groupId and packaging in order to be more transparent.
The most important parts are properties and resources. The second property is called "my.timestamp", but that is just my nickname for it and you can change it if you want as long as you change also the same value in the properties file, of course.
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 <version>0.0.1-SNAPSHOT</version>
 <name>omega</name>
 <properties>
  <maven.build.timestamp.format>dd.MM.yyyy HH.mm</maven.build.timestamp.format>
  <my.timestamp>${maven.build.timestamp}</my.timestamp>
 </properties>
 <build>
  <resources>
   <resource>
    <directory>src/main/resources</directory>
    <filtering>true</filtering>
   </resource>
  </resources>
 </build>
</project>
Firstly, I define maven's propety "maven.build.timestamp.format", because there is no default for that, secondly I set build time into a variable (in my example "my.timestamp"), because you can not just put "maven.build.timestamp" property into the filtered file.

Outcome

And this is how the filtered file looks like after the build process.
version=0.0.1-SNAPSHOT
buildtime=10.12.2012 21.26

Conclusion

Adding version and build time into an application is a simple matter, especially when you are already using a properties file. Maven offers fairly simple, but not so intuitive way, how to include build time and version record during the build and it can be handy to have this information somewhere in an application.
I am not discussing means for loading a properties file into the application because it is very dependent on frameworks you use.

Note

The variable "maven.build.timestamp" is usable only since Maven 2.1.0-M1. You would probably need to run an ant task in previous Maven versions.

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