How can I use properties exactly as they are provided by the io.fabric8 docker-maven-plugin?

Maven properties filled in by io.fabric8 docker-maven-plugin seem not to be interpolated when used as is.

The docker-maven-plugin fills in some maven properties (some.host and some.port) which I try to resolve.

<plugin>
    <groupId>io.fabric8</groupId>
    <artifactId>docker-maven-plugin</artifactId>
    <version>0.15.5</version>
    <configuration>
        <images>
            <image>
                <alias>...</alias>
                <name>...</name>
                <run>
                    <ports>
                        <port>+some.host:some.port:5432</port>
                    </ports>
                    <namingStrategy>alias</namingStrategy>
                </run>
            </image>
        </images>
    </configuration>
</plugin>

They are used like this:

<properties>
    <docker.host>${some.host}</docker.host>
    <docker.port>${some.port}</docker.port>
</properties>

which leads to two empty values. They contain nothing while they should contain e.g. 127.0.0.1 and 5555.

If I add some characters, suddenly the values are interpolated correctly (but of course the values are useless then)

<properties>
    <docker.host>${some.host}+abc</docker.host>
    <docker.port>${some.port}+123</docker.port>
</properties>

which leads to 127.0.0.1+abc and 5555+123

Some things I tried don't work either:

<properties>
    <dollar>$</dollar>
    <docker.host>${dollar}{some.host}</docker.host>
    <docker.port>${some.port}${}</docker.port>
</properties>

which leads to an empty value and 5555null

Solution

Roland Huß noted that the problem could be avoided by using dockers fixed ports. And that should be the first choice.

But for completion, I'll add a solution that also works:

Trick maven into creating an empty property (e.g., using the groovy-maven-plugin)

    <plugin>
        <groupId>org.codehaus.gmaven</groupId>
        <artifactId>groovy-maven-plugin</artifactId>
        <version>2.0</version>
        <executions>
            <execution>
                <id>set empty property</id>
                <phase>initialize</phase>
                <goals>
                    <goal>execute</goal>
                </goals>
                <configuration>
                    <source>
                            <![CDATA[
                        project.properties.setProperty('empty', '');
                        ]]>
                        </source>
                </configuration>
            </execution>
        </executions>
    </plugin>

Use the empty property to make maven interpolate the properties exposed by the docker-maven-plugin
```
<docker.host>${some.host}${empty}</docker.host>
<docker.port>${some.port}${empty}</docker.port>
```