How to access maven.build.timestamp for resource filtering - maven

Question

I am using maven 3.0.4 and would like to make the build timestamp accessible to my application. For this, I'm putting a placeholder in a .properties file and let maven filter on build. While this is working fine for ${project.version}, ${maven.build.timestamp} is not substituted on filtering.
The property seems to be available on build - I can use it to modify the artifact name:
<finalName>${project.artifactId}-${maven.build.timestamp}</finalName>
So why is it not available for resource filtering? And, more importantly, how do I make it accessible?

Answer 1

I have discovered this article, explaining that due to a bug in maven, the build timestamp does not get propagated to the filtering. The workaround is to wrap the timestamp in another property:
<properties>
<timestamp>${maven.build.timestamp}</timestamp>
<maven.build.timestamp.format>yyyy-MM-dd HH:mm</maven.build.timestamp.format>
</properties>
Filtering then works as expected for
buildTimestamp=${timestamp}

Answer 2

I can confirm as of Maven 3.x {maven.build.timestamp} is "working" now. They work arounded the problem, apparently. No additional properties workaround needed anymore.
However, be careful your "filtering" plugin (maven-resources-plugin) is up to date. It needs to be relatively new, so if mvn help:effective-pom shows an old version (ex: 2.6), bump it to something newer, fixed it for me, 3.x ex:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-resources-plugin</artifactId>
<version>3.1.0</version>
</plugin>
<properties><timestamp>... workaround is no longer required...
This also cleared up, kind of, why it was working in IntelliJ but not the command line. IntelliJ probably uses their own "modified/internal" maven constants, so it was working there, but not from maven command line.
Also note if you add a filtering resource directory to you pom, you may need to also "re-add" the default directory, it gets lost, ex:
<resource>
<directory>src/main/resources-filtered</directory> <!-- to get "maven.build.timestamp" into resource properties file -->
<filtering>true</filtering>
</resource>
<resource>
<directory>src/main/resources</directory> <!-- apparently have to add this is you have the other... -->
</resource>
NB if you're using spring boot as your parent, you have to use #maven.build.timestamp# instead. Also note if you're using spring boot there's a file META-INF/build-info.properties that is optionally created by the spring-boot-maven-plugin that you can read (spring provides a BuildProperties bean for convenience reading it).

Answer 3

In order to enrich the Stackoverflow content for others, that like me, found this post as a way to solve the "problem" of ${maven.build.timestamp}. This is not a maven bug, but an expected behavior of m2e, as can be seen in this post.
Therefore, I believe that we can not expect the solution to be "corrected", since, from what I understand, the correction involves conceptual issues.
In my case, what I did was use the plugin (buildnumber-maven-plugin) as described in this other post.

Answer 4

Adding Maven properties at the pom project level doesn't take into account correct local Timezone, so timestamp may appear wrong :
<properties><timestamp>${maven.build.timestamp}</timestamp></properties>
Using the build-helper-maven-plugin applies the correct timezone and current daylight saving to the timestamp :
<build>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>build-helper-maven-plugin</artifactId>
<version>1.9.1</version>
<executions>
<execution>
<id>timestamp-property</id>
<goals>
<goal>timestamp-property</goal>
</goals>
<configuration>
<name>timestamp</name>
<pattern>yyyy-MM-dd HH:mm:ss</pattern>
<timeZone>Europe/Zurich</timeZone>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
<resources>
<resource>
<directory>src/main/resources</directory>
<filtering>true</filtering>
</resource>
</resources>
</build>
When packaging, Maven will replace any token timestamp in /resources folder, e.g. resources/version.properties :
build.timestamp=${timestamp}
You can then load this properties file in your Application.