CODEWITHSUNDEEP
mavenpom.xml
jakub.g
jakub.g

Reputation: 41268

Maven variables precedence: how to make env variable being more important than hardcoded value in pom.xml?

I'd like to implement, in maven, a way of passing variables to POM via env variable but using a default value if not provided.

I created a minimalitic pom.xml that prints FOO and FOOBAR vars. FOOBAR has a default value:

<project>
    <groupId>com.example</groupId>
    <artifactId>test</artifactId>
    <version>sprint-SNAPSHOT</version>
    <modelVersion>4.0.0</modelVersion>
    <properties>
        <FOOBAR>1111111</FOOBAR>
    </properties>
    <build><plugins><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-antrun-plugin</artifactId><version>1.1</version>
        <executions><execution>
                <phase>validate</phase><goals><goal>run</goal></goals>
                <configuration><tasks>
                        <echo>FOO = ${FOO}</echo>
                        <echo>FOOBAR = ${FOOBAR}</echo>
                </tasks></configuration>
        </execution></executions>
    </plugin></plugins></build>
</project>

Now, let’s try to run by passing a value from command line, or via env variable:

me@mymachine /d/mvn-tests
$ mvn install | grep FOO
     [echo] FOO = ${FOO}
     [echo] FOOBAR = 1111111

me@mymachine /d/mvn-tests
$ mvn install -DFOO=999 | grep FOO
     [echo] FOO = 999
     [echo] FOOBAR = 1111111

me@mymachine /d/mvn-tests
$ FOO=999 mvn install | grep FOO
     [echo] FOO = 999
     [echo] FOOBAR = 1111111

me@mymachine /d/mvn-tests
$ mvn install -DFOOBAR=555 | grep FOO
     [echo] FOO = ${FOO}
     [echo] FOOBAR = 555

me@mymachine /d/mvn-tests
$ FOOBAR=555 mvn install | grep FOO
     [echo] FOO = ${FOO}
     [echo] FOOBAR = 1111111

The last scenario is the one I don’t like: I’d prefer the env variable to take precedence over the property defined in the top of the XML (I want the one hardcoded in the XML to be the last-resort check).

So it seems that maven’s precedence is as follows:

Command line param > hardcoded XML value > env variable

I’d like to have:

Command line param > env variable > hardcoded XML value

Is there a way I can achieve the behaviour I want?

I’ve noticed I can use env.FOOBAR to point unambiguously to the env variable:

...
    <echo>FOO = ${FOO}</echo>
    <echo>FOOBAR = ${FOOBAR}</echo>
    <echo>env.FOOBAR = ${env.FOOBAR}</echo>

And then

me@mymachine /d/mvn-tests
$ FOOBAR=15 mvn install | grep FOO
[echo] FOO = ${FOO}
[echo] FOOBAR = 1111111
[echo] env.FOOBAR = 15

But how to say in pom.xml sth that in a JS file would be ${env.FOOBAR || FOOBAR} i.e. take one from env, if not specified, then take other one?

Upvotes: 1

Views: 340

Answers (1)

carlspring
carlspring

Reputation: 32607

I think you'd be better off using Maven Profiles and defining the behavior/values based on that. Have a look at the documentation.

This way you'll be able to fine-tune the variables as you wish.

Upvotes: 2

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