Caused by: Java.sql.SQLException: Field ‘id’ doesn’t have a default value

如果主鍵的生成策略採取的是identity，而資料庫中表的主鍵不是自動生成機制，則報這樣的錯誤

org.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session: [cn.itcast.hibernate717.helloworld.Person#1]

如果在hibernate中，有兩個物件，但是其ID值是相同的，這樣的情況在hibernate中是不允許出現 （在hibernate中，強調物件的唯一性）

Caused by: java.sql.BatchUpdateException: Cannot delete or update a parent row: a foreign key constraint fails (test/orders, CONSTRAINT FKC3DF62E58940CCE2 FOREIGN KEY (customer_id) REFERENCES customer (id))

違反了主外來鍵約束的原則

org.hibernate.LazyInitializationException: could not initialize proxy - no Session

org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: cn.itcast.hibernate717.manytomany.Student