MavenProject project = (MavenProject) getPluginContext().get("project");
String projectDir=project.getBasedir().toString();

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-war-plugin</artifactId>
  <version>2.5</version>
  <executions>
    <execution>
      <id>prepare-war</id>
      <phase>prepare-package</phase>
        <goals>
          <goal>exploded</goal>
        </goals>
    </execution>
  </executions>
  <configuration>
    <useCache>true</useCache>
 </configuration>
</plugin>

<plugin>
    <groupId>...</groupId>
    <artifactId>...</artifactId>
    <version>....</version>
    <executions>
    <execution>
        <phase>prepare-package</phase>
        <goals>
            <goal>...</goal>
        </goals>
        </execution>
    </executions>
</plugin>