Maven - Suppress [WARNING] JAR will be empty - no content was marked for inclusion in pom.xml

The warning is actually based on whether it can find the configured <classesDirectory> - by default target\classes.

This means one simple way to bypass the warning is to point it at another deliberately empty directory:

<build>
    <plugins>
        <plugin>
            <artifactId>maven-jar-plugin</artifactId>
            <configuration>
                <classesDirectory>dummy</classesDirectory>
            </configuration>
        </plugin>
    </plugins>
</build>

Alternatively, to avoid the need for the empty directory, exclude everything from another directory:

        <plugin>
            <artifactId>maven-jar-plugin</artifactId>
            <configuration>
                <classesDirectory>src</classesDirectory>
                <excludes>
                    <exclude>**</exclude>
                </excludes>
            </configuration>
        </plugin>

Both solutions suppressed the warning message programmatically.

Solution 1:

<!-- https://mvnrepository.com/artifact/org.apache.maven.plugins/maven-jar-plugin -->
<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-jar-plugin</artifactId>
    <version>3.1.0</version>
    <!-- Ignore src/main in JAR packaging -->
    <configuration>
        <classesDirectory>src</classesDirectory>
        <excludes>
            <exclude>main</exclude>
        </excludes>
    </configuration>
</plugin>

Solution 2:

Since the above essentially created an empty JAR (and I did not really want to include test classes and test resources), I opted to "skip" the JAR creation instead.

What is the best way to avoid maven-jar?

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-jar-plugin</artifactId>
    <version>3.1.0</version>
    <executions>
        <execution>
            <id>default-jar</id>
            <phase>none</phase>
        </execution>
    </executions>
</plugin>

This is (according to me) the cleanest solution
for projects that don't contain production code but do contain tests:

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-jar-plugin</artifactId>
                <configuration>
                    <skipIfEmpty>true</skipIfEmpty>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-install-plugin</artifactId>
                <configuration>
                    <skip>true</skip>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-deploy-plugin</artifactId>
                <configuration>
                    <skip>true</skip>
                </configuration>
            </plugin>
        </plugins>
    </build>

It indicates what you want:

• to skip trying to package "no production code" into a jar
• don't try to install/deploy the non-existing jar

leaving test execution untouched.

---

Like @John Camerin mentioned it is NOT advised to use <packaging>pom</packaging>
unless the ONLY thing your pom should do is gather dependencies.
Otherwise, if you have tests, they would be skipped without warning, which is not what you want.