Update query in jpa using composite primary key. ask question. up vote 1 down vote favorite. 1. i have an entity student with a composite primary key (indid, studentid). i want to update some rows in this table. i am not sure how to write an update query (using jpa) when using a composite primary key. looking for suggestions. thanks.. Jpa assumes that the primary key is fixed. the read, updated and delete operations identifies the object in question by it's id. if you change the id of an object and execute an update, jpa either updates some completely different object (and this might result in an exception) or doesn't find an object to update at all.. I have a mysql table without primary key, and i have to map it into a jpa entity. i cannot modify the table in any way. because entities must have a primary key, i have to specify one..
A generic list could be used to pass the primary key to find() methods, and it would be the jpa provider's responsibility for hashing and comparing the primary key correctly instead of the user's idclass. but perhaps for simple singleton primary key models the jpa model is more straight forward.. Hi, i have some classes .every classes have its own primary key.i saved a entity in the db.i want to add a new entity in the db with the existing one just changed one classes id. main idea is every data will be same just changed the user id.but jpa does not save a entity its update every time.what is the logic ??. Before you use entity manager to make a jpa entity persistent, you must create a primary key for the entity. about this task if you have a jpa dao implementation which extends abstractjpaentitydaoimpl , you can use myjpadao.generateprimarykey("mytable") to generate primary key for your new jpa entity..
