why list the goals of a plugin without binding to a phase?

Question

Please consider this pom excerpt taken from jacoco example ( http://www.eclemma.org/jacoco/trunk/doc/examples/build/pom-it.xml)

    <plugins>
    <plugin>
        <groupId>org.jacoco</groupId>
        <artifactId>jacoco-maven-plugin</artifactId>
        <version>0.7.5-SNAPSHOT</version>
        <executions>
            <execution>
                <id>default-prepare-agent</id>
                <goals>
                    <goal>prepare-agent</goal>
                </goals>
            </execution>
            <execution>
                <id>default-prepare-agent-integration</id>
                <goals>
                    <goal>prepare-agent-integration</goal>
                </goals>
            </execution>
            <execution>
                <id>default-report</id>
                <goals>
                    <goal>report</goal>
                </goals>
            </execution>
            <execution>
                <id>default-report-integration</id>
                <goals>
                    <goal>report-integration</goal>
                </goals>
            </execution>
            <execution>
                <id>default-check</id>
                <goals>
                    <goal>check</goal>
                </goals>
                <configuration>
                    <rules>
                        <!--  implmentation is needed only for Maven 2  -->
                        <rule implementation="org.jacoco.maven.RuleConfiguration">
                            <element>BUNDLE</element>
                            <limits>
                                <!--  implmentation is needed only for Maven 2  -->
                                <limit implementation="org.jacoco.report.check.Limit">
                                    <counter>COMPLEXITY</counter>
                                    <value>COVEREDRATIO</value>
                                    <minimum>0.60</minimum>
                                </limit>
                            </limits>
                        </rule>
                    </rules>
                </configuration>
            </execution>
        </executions>
    </plugin>
    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-surefire-plugin</artifactId>
        <version>2.16</version>
    </plugin>
    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-failsafe-plugin</artifactId>
        <version>2.16</version>
        <executions>
            <execution>
                <id>default-integration-test</id>
                <goals>
                    <goal>integration-test</goal>
                </goals>
            </execution>
        </executions>
    </plugin>
</plugins>

Now I know that you can bind a plugin's goal to a maven phase, that is run that goal when maven executes a specific phase.

What is the point of just listing the integration-test goal for the maven failsafe plugin without binding it to something?

The same as for jacoco report and others goal? I don't think you can force the plugin to execute just those listed goals right?

Many thanks

Answer 1

The point is that a plugin can define default life cycle phases where the appropriate goal is bound to (many plugins do this). In this cases you don't need to specify the life cycle phase within the pom file explicitly.

For example the maven-failsafe-plugin has a goal integration-test. This goal has a default binding to the integration-test life cycle phase. Here an excerpt from the documentation:

Description:

Run integration tests using Surefire. Attributes:

• Requires a Maven project to be executed.
• Requires dependency resolution of artifacts in scope: test.
• The goal is thread-safe and supports parallel builds.
• Binds by default to the lifecycle phase: integration-test.

That's the reason why you don't need to give a life cylce phase in the configuration like this:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-failsafe-plugin</artifactId>
    <version>2.18.1</version>
    <executions>
        <execution>
            <id>default-integration-test</id>
            <goals>
                <goal>integration-test</goal>
            </goals>
        </execution>
    </executions>
</plugin>

The same is meant for the jacoco maven plugin.