How do I run the maven exec plugin multiple times in a build

Question

Below is the relevant part of my POM -

<plugin>
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>exec-maven-plugin</artifactId>
    <version>1.5.0</version>
    <executions>
        <execution>
            <id>StartHub</id>
            <phase>test</phase>
            <goals>
                <goal>exec</goal>
            </goals>
            <configuration>
                <executable>java</executable>
                <arguments>
                    <argument>-jar</argument>
                    <argument>${basedir}/src/lib/Hub/selenium-server-standalone-2.53.0.jar</argument>
                    <argument>-role</argument>
                    <argument>hub</argument>
                    <argument>-throwOnCapabilityNotPresent</argument>
                    <argument>false</argument>
                    <argument>-newSessionWaitTimeout</argument>
                    <argument>20000</argument>
                </arguments>
            </configuration>
        </execution>
        <execution>
            <id>StartNode</id>
            <phase>test</phase>
            <goals>
                <goal>exec</goal>
            </goals>
            <configuration>
                <executable>java</executable>
                <arguments>
                    <argument>-jar</argument>
                    <argument>${basedir}/src/lib/Node/selenium-server-standalone-2.53.0.jar</argument>
                    <argument>-hub</argument>
                    <argument>http://127.0.0.1:4444/register/grid</argument>
                    <argument>-port</argument>
                    <argument>5555</argument>
                    <argument>
                        Dwebdriver.chrome.driver=${basedir}/chromedriver.exe</argument>
                </arguments>
            </configuration>
        </execution>
    </executions>
</plugin>

I was trying to use the exec plugin to execute a jar(selenium standalone server) in two configurations(hub and Node).

My issue is that the jar is executed only once in the configuration specified between the first pair of "execution" tags. I have searched extensively for a solution and the only thing I found was that the id's for different executions need to be different, which I rectified. I still can't seem to manage to run the jars twice even though I can run any one of them successfully if I comment out the execution of the other.

I should also mention that I'm running the project in Eclipse, so ideally what I would want to do is right-click on the POM.xml click on Run-as and select "Maven test".

Answer 1

This is not a Maven executions issue but rather an issue related to what you are executing: a blocking process (the first server) which would stop the build listening for a node which would never get connected (because its execution won't start).

Changing your pom to the following:

<plugin>
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>exec-maven-plugin</artifactId>
    <version>1.5.0</version>
    <executions>
        <execution>
            <id>StartHub</id>
            <phase>test</phase>
            <goals>
                <goal>exec</goal>
            </goals>
            <configuration>
                <executable>java</executable>
                <arguments>
                    <argument>-version</argument>
                </arguments>
            </configuration>
        </execution>
        <execution>
            <id>StartNode</id>
            <phase>test</phase>
            <goals>
                <goal>exec</goal>
            </goals>
            <configuration>
                <executable>java</executable>
                <arguments>
                    <argument>-version</argument>
                </arguments>
            </configuration>
        </execution>
    </executions>
</plugin>

It would perfectly execute the two exec executions, printing twice the Java version. Note: the snippet is a copy and paste from your question, just replacing arguments of the java command to its version option.

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What you are most probably looking for is to execute the two commands in background or at least in a non-blocking way in order to get the second executed, then proceed with the build (to execute some tests I presume).

Check this SO question on how to achieve it: instead of using the exec-maven-plugin, use the maven-antrun-plugin to launch the two selenium commands.

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As a further note, you should probably consider using the maven-failsafe-plugin instead and execute integration tests, attaching the executions above to the pre-integration-test phase and stop them during the post-integration-test phase in order to properly clean them.