Java JPA error: No Persistence provider for EntityManager named

While working on a JPA project, this type error keeps popping up despite that fact that the persistence unit name is correctly specified. At first, I thought I may miss some jar files or class path problem. However, it turned out that the persistence.xml need to be placed under src/main/resources/META-INF folder (if META-INF is not there, you need to create one).