Because Maven 1 repositories have artifacts without POMs, the following occurs on browse:

2008-03-25 19:35:22,409 [btpool0-3] ERROR org.apache.maven.archiva.consumers.DatabaseUnprocessedArtifactConsumer:update-db-project - Unable to process model /Users/brett/scm/maven/archiva-1.0.x/archiva-web/archiva-webapp/target/appserver-base/data/repositories/m1/app/poms/app-1.0.pom due to : javax.jdo.JDOUserException : Field org.apache.maven.archiva.model.ArchivaProjectModel.packaging is null, but is mandatory as its described in the jdo metadata
javax.jdo.JDOUserException: Field org.apache.maven.archiva.model.ArchivaProjectModel.packaging is null, but is mandatory as its described in the jdo metadata
at org.jpox.store.rdbms.fieldmanager.ParameterSetter.storeStringField(ParameterSetter.java:120)
at org.jpox.state.StateManagerImpl.providedStringField(StateManagerImpl.java:2757)
at org.apache.maven.archiva.model.ArchivaProjectModel.jdoProvideField(ArchivaProjectModel.java)
at org.apache.maven.archiva.model.ArchivaProjectModel.jdoProvideFields(ArchivaProjectModel.java)
at org.jpox.state.StateManagerImpl.provideFields(StateManagerImpl.java:3115)
at org.jpox.store.rdbms.request.InsertRequest.execute(InsertRequest.java:252)
at org.jpox.store.rdbms.table.ClassTable.insert(ClassTable.java:2519)
at org.jpox.store.StoreManager.insert(StoreManager.java:938)
at org.jpox.state.StateManagerImpl.internalMakePersistent(StateManagerImpl.java:3667)
at org.jpox.state.StateManagerImpl.makePersistent(StateManagerImpl.java:3646)
at org.jpox.AbstractPersistenceManager.internalMakePersistent(AbstractPersistenceManager.java:1206)
at org.jpox.AbstractPersistenceManager.makePersistent(AbstractPersistenceManager.java:1277)
at org.apache.maven.archiva.database.jdo.JdoAccess.saveObject(JdoAccess.java:192)
at org.apache.maven.archiva.database.jdo.JdoAccess.saveObject(JdoAccess.java:165)
at org.apache.maven.archiva.database.jdo.JdoProjectModelDAO.saveProjectModel(JdoProjectModelDAO.java:86)
at org.apache.maven.archiva.consumers.database.ProjectModelToDatabaseConsumer.processArchivaArtifact(ProjectModelToDatabaseConsumer.java:170)
at org.apache.maven.archiva.database.updater.ProcessArchivaArtifactClosure.execute(ProcessArchivaArtifactClosure.java:52)
at org.apache.commons.collections.CollectionUtils.forAllDo(CollectionUtils.java:388)
at org.apache.maven.archiva.database.updater.JdoDatabaseUpdater.updateUnprocessed(JdoDatabaseUpdater.java:154)
at org.apache.maven.archiva.database.browsing.DefaultRepositoryBrowsing.selectVersion(DefaultRepositoryBrowsing.java:124)
at org.apache.maven.archiva.web.action.ShowArtifactAction.artifact(ShowArtifactAction.java:105)

A placeholder should be used instead