I'm working on APF-565 (allowing dao.framework switching) and
experiencing an issue with the hibernate3 plugin.

Here's how I'm excluding Hibernate and including JPA in my sample project:

<dependency>
           <groupId>org.appfuse</groupId>
           <artifactId>appfuse-${web.framework}</artifactId>
           <version>${appfuse.version}</version>
           <type>warpath</type>
           <exclusions>
               <exclusion>
                   <groupId>org.appfuse</groupId>
                   <artifactId>appfuse-hibernate</artifactId>
               </exclusion>
           </exclusions>
       </dependency>
       <dependency>
           <groupId>org.appfuse</groupId>
           <artifactId>appfuse-${dao.framework}</artifactId>
           <version>${appfuse.version}</version>
       </dependency>

Here's the error I'm getting:

[INFO] ------------------------------------------------------------------------
[INFO] No name provided and several persistence units found
[INFO] ------------------------------------------------------------------------
[INFO] Trace
javax.persistence.PersistenceException: No name provided and several
persistence units found
       at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:226)
       at org.codehaus.mojo.hibernate3.configuration.JPAComponentConfiguration.createConfiguration(
JPAComponentConfiguration.java:26)
       at org.codehaus.mojo.hibernate3.configuration.AbstractComponentConfiguration.getConfiguratio
n(AbstractComponentConfiguration.java:32)
       at org.codehaus.mojo.hibernate3.exporter.Hbm2DDLExporterMojo.doExecute(Hbm2DDLExporterMojo.j
ava:87)
       at org.codehaus.mojo.hibernate3.HibernateExporterMojo.execute(HibernateExporterMojo.java:139

In pom.xml, I have:

<plugin>
               <groupId>org.codehaus.mojo</groupId>
               <artifactId>hibernate3-maven-plugin</artifactId>
               <version>2.0-alpha-1</version>
               <configuration>
                   <components>
                       <component>
                           <name>hbm2ddl</name>
                           <implementation>jpaconfiguration</implementation>
                       </component>
                   </components>
                   <componentProperties>
                       <drop>true</drop>
                       <jdk5>true</jdk5>

<propertyfile>target/classes/jdbc.properties</propertyfile>
                       <skip>${maven.test.skip}</skip>
                   </componentProperties>
               </configuration>
               <executions>
                   <execution>
                       <phase>process-test-resources</phase>
                       <goals>
                           <goal>hbm2ddl</goal>
                       </goals>
                   </execution>
               </executions>
               <dependencies>
                   <dependency>
                       <groupId>${jdbc.groupId}</groupId>
                       <artifactId>${jdbc.artifactId}</artifactId>
                       <version>${jdbc.version}</version>
                   </dependency>
               </dependencies>
           </plugin>