Intellij中spring jpa entity "cannot resolve symbol"

see this link: http://stackoverflow.com/questions/12420996/intellij-idea-highlights-entity-class-names-with-cannot-resolve-symbol-in-jp

选择project structure中的facet，新建JPA，新增一个JPA Provider的persistence.xml，打开intellij左侧的persistence，右键选择new -> Persistence Unit，done。