It seems there is no equivalent of Python App Engine\'s _ah/admin for the Java implementation of Google App Engine.
Is there a manual way I can browse the datastore?
There's currently no datastore viewer for the Java SDK - one should be coming in the next SDK release. In the meantime, your best bet is to write your own admin interface with datastore viewing code - or wait for the next SDK release.
Java App Engine now has a local datastore viewer, accessible at http://localhost:8080/_ah/admin
.