Problem Description:
java.lang.IllegalArgumentException: The given id must not be null!
problem analysis:
1. When using JPA's own method of obtaining data based on the primary key ID to pass parameters, null values cannot be passed.
java.lang.IllegalArgumentException: The given id must not be null!
1. When using JPA's own method of obtaining data based on the primary key ID to pass parameters, null values cannot be passed.