MavenprojectJPA:PersistvsMerge -> http://www.17cats.com/newblog/tags/%E6%9E%97%E5%BF%83%E5%A6%82/?end=165829663&peo=165829663&date=g1VxuO4vYDGiPiKW&bx=9ch4Xv4eXUy2aTEI