MavenprojectJPA:PersistvsMerge -> http://www.17cats.com/newblog/post/5b2ca064/?ie=63db5b70-28fd-4408-808a-5650789b740c&pso=8taoyGsfVSHVrG3a&avg=1658276399&bx=GvazaLqvlptTgRPy&ie=ba807488-c3e7-4be9-b203-2ff86bf1edd6