I have encountered this exception before. I didn't know how to do it before, so I went online to check it. This time I encountered this exception again. I am determined to trace the source and find the origin of the problem.
A different object with the same Identifier value was already associated with the session
This error means that two different objects are associated with the same flag, that is, two objects exist in a session, however, the flag spaces of these two objects are the same. For example, the IDs of the two objects are the same, and this is the unique primary key of the database. conflicts occur during the update operation, because hibernate does not know which object to update, this exception is reported.
The following answers are provided for searching on the Internet:
Solution 1: Session. Clean ()
PS: If saveorupdate (object) and other operations to change the data status are performed after the clean operation, the "found two representations of same Collection" exception may be reported.
Solution 2: Session. Refresh (object)
PS: when the object is not an existing data object in the database, the session cannot be used. refresh (object) because this method is used to retrieve the object from the hibernate session, if this object does not exist in the session, an error is returned. Therefore, when you use saveorupdate (object) you need to judge before.
Solution 3: Session. Merge (object)
PS: the built-in methods in hibernate are recommended. My analysis: We usually write this exception in the program. First, we get the object passed from the page. We call it VO (view object ), then we call the hibernate method to query the database and obtain the entity class that is the same as the VO primary key. We call it Po, and then we get the attribute in the Po and assign the value to the VO attribute, finally, we call the hibernate method to update Vo, and this exception is reported. The reason for this is that the cache of the hibernate session contains both the VO object and the Po object, and their IDs are the same, so hibernate does not know the update. The final solution is to operate on the object class Po queried from the database, and call the Set Method in the Po object class to copy the property to be updated, in this way, an object will be maintained in the hibernate session. Do not create an object completely, or assign VO to the object class. This error will also be reported. Because after copying or new objects, there will be two more objects in the hibernate session.
