The appc mojo requires the tools.jar to run.  Many systems provide the tools.jar as part of the
installation such as the Apple Mac.  If you are not running on a MAC you will need to configure the
tools jar in either your pom.xml or in your settings.xml.  The tools jar used to be included in the 
pom.xml for the plugin but it caused issues with the mac so it was removed and this note added.

in your settings.xml add a profile entry to discover what platform you are running on.

<profiles>
    <profile>
      <id>default-tools.jar</id>
      <activation>
        <property>
          <name>java.vendor</name>
          <value>Sun Microsystems Inc.</value>
       </property>
     </activation>
      <dependencies>
        <dependency>
          <groupId>com.sun</groupId>
          <artifactId>tools</artifactId>
          <version>1.5.0</version>
          <scope>system</scope>
          <systemPath>${java.home}/../lib/tools.jar</systemPath>
       </dependency>
     </dependencies>
   </profile>
 </profiles>


in the pom.xml include a dependency 

<dependency>
    <groupId>com.sun</groupId>
    <artifactId>tools</artifactId>
    <version>1.5.0</version>
    <scope>system</scope>
    <systemPath>${java.home}/../lib/tools.jar</systemPath>
</dependency>


A sample configuration might be:
...
<plugin>
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>weblogic-maven-plugin</artifactId>
    <version>2.9.1-SNAPSHOT</version>
    <configuration>
        <contextUri>mycontext</contextUri>
        <warName>myWarName-${pom.version}.war</warName>
        <verbose>true</verbose>
        <services>
            <service>
                <includeEJBs>MyEJB</includeEJBs>
                <serviceName>MyEJBService</serviceName>
                <serviceUri>/MyServiceURI</serviceUri>
                <targetNamespace>
                    http://my.service.com/wsdl
                </targetNamespace>
            </service>
            <service>
                ... additional services as required
            </service>
        </services>
    </configuration>
    <executions>
        <execution>
            <phase>package</phase>
            <goals>
                <goal>servicegen</goal>
                <goal>appc</goal>
            </goals>
        </execution>
    </executions>
</plugin>
...