How to wrap an Ant build with Maven?

You can actually wrap an ANT project with Maven by using multiple ant run goals as I wrote in a different question. Assuming your existing ant project has clean and build tasks, this might be a useful way of wrapping the project so you can use maven goals and have it map to existing ant code.

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-install-plugin</artifactId>
    <version>2.3.1</version>
    <executions>
        <execution>
            <id>install-library</id>
            <phase>install</phase>
            <goals>
                <goal>install-file</goal>
            </goals>
            <configuration>
                <groupId>x.x</groupId>
                <artifactId>ant-out-atifacts</artifactId>
                <version>${project.version}</version>
                <file>ant-output.jar</file>
                <packaging>zip</packaging>
            </configuration>
        </execution>
    </executions>
</plugin>

You can use the maven-antrun-plugin to invoke the ant build. Then use the build-helper-maven-plugin to attach the jar produced by ant to the project. The attached artifact will be installed/deployed alongside the pom.
If you specify your project with packaging pom, Maven will not conflict with the ant build.

In the example below, the ant build.xml is assumed to be in src/main/ant, have a compile goal, and output to ant-output.jar.

<plugin>
  <artifactId>maven-antrun-plugin</artifactId>
  <executions>
    <execution>
      <phase>process-resources</phase>
      <configuration>
        <tasks>
          <ant antfile="src/main/ant/build.xml" target="compile"/>
        </tasks>
      </configuration>
      <goals>
        <goal>run</goal>
      </goals>
    </execution>
  </executions>
</plugin>
<plugin>
  <groupId>org.codehaus.mojo</groupId>
  <artifactId>build-helper-maven-plugin</artifactId>
  <version>1.3</version>
  <executions>
    <execution>
      <id>add-jar</id>
      <phase>package</phase>
      <goals>
        <goal>attach-artifact</goal>
      </goals>
      <configuration>
        <artifacts>
          <artifact>
            <file>${project.build.directory}/ant-output.jar</file>
            <type>jar</type>
          </artifact>
        </artifacts>
      </configuration>
    </execution>
  </executions>
</plugin>