pom.xml environment variable with default fallback

Question

I would like to be able to use an environment variable if it's set or a default fallback value that I set in pom.xml similar to ${VARIABLE:-default} in bash. Is it possible? Something like:

${env.BUILD_NUMBER:0}

There is a good answer here: http://stackoverflow.com/a/13709976/868456 — Dimath, Mar 17 '16 at 08:58
@Dimath solutions seems to be much easier than the proposed answer here.. — lifeofguenter, Jan 26 '18 at 07:53

score 48 · Answer 1 · answered Nov 23 '16 at 04:41

I wasn't really satisfied with the accepted approach, so I simplified it a little.

Basically set a default property in the normal properties block, and only override when appropriate (instead of an effective switch statement):

<properties>
     <!-- Sane default -->
    <buildNumber>0</buildNumber>
    <!-- the other props you use -->
</properties>

<profiles>
    <profile>
        <id>ci</id>
        <activation>
            <property>
                <name>env.buildNumber</name>
            </property>
        </activation>
        <properties>
            <!-- Override only if necessary -->
            <buildNumber>${env.buildNumber}</buildNumber>
        </properties>
    </profile>
</profiles>

score 24 · Accepted Answer · edited Jan 13 '16 at 08:05

24

You could use profiles to achieve this:

<profiles> 
    <profile>
        <id>buildnumber-defined</id>
        <activation>
            <property>
                <name>env.BUILD_NUMBER</name>
            </property>
        </activation>
        <properties>
            <buildnumber>${env.BUILD_NUMBER}</buildnumber>
        </properties>
    </profile>
    <profile>
        <id>buildnumber-undefined</id>
        <activation>
            <property>
                <name>!env.BUILD_NUMBER</name>
            </property>
        </activation>
        <properties>
            <buildnumber>0</buildnumber>
        </properties>
    </profile>
</profiles>

A bit more verbose than bash...

edited Jan 13 '16 at 08:05

Gavriel

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answered Jan 12 '16 at 15:30

StephaneM

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As far as I know I would need to pass `mvn -P buildnumber-undefined`, don't I? How would I use it later in the pom.xml? – Gavriel Jan 12 '16 at 15:35
The appropriate profile will be activated based on the existence or non-existence of the environment variable `BUILD_NUMBER`. Afterwards the property `buildnumber` should be defined in your pom and can be accessed with `${buildnumber}`. – StephaneM Jan 12 '16 at 15:39
3

As far as I know, you don't need two profiles for this (at least in recent maven releases). You can provide a default in the top level `` and then it's only overridden with the custom activation (the first profile in this answer). Saves 11 lines :) – nerdwaller Aug 17 '16 at 17:37
@nerdwaller can you please provide an example? Yours sounds like a better approach. – eggonlegs Nov 22 '16 at 20:45
1

@eggonlegs - added as an answer so the formatting would show. – nerdwaller Nov 23 '16 at 04:42

pom.xml environment variable with default fallback

2 Answers2