Data was not saved object references an unsaved transient instance - save the transient instance before flushing

Question

I have a database with two tables User and Country  I want to relationship where many user can belong to one county  I implement this using hibernate using the following model classes     Entity  name    user   public class User        Id  GeneratedValue  strategy   GenerationType IDENTITY      private int userId      private String username      private String password       ManyToOne        JoinColumn  name    countryId      private Country country         Getter  amp  Setter       Entity  name    country   public class Country         Id  GeneratedValue strategy   GenerationType IDENTITY      private int countryId      private String countryName       Getter  amp  Setter     When I try to save the user object I get the following exception     org hibernate HibernateException  Data was not saved  object references an unsaved transient instance - save the transient instance before flushing  com kyrogaming models Country   How can I fix the problem

User · Answer

It should be CascadeType Merge  in that case it will update if the record already exists

User · Answer

Looks like Users that are added in your Country object  are not already present in the DB  You need to use cascade to make sure that when Country is persisted  all User which are not there in data but are associated with Country also get persisted   Below code should help    ManyToOne  cascade   CascadeType ALL      JoinColumn  name    countryId      private Country country

User · Answer

I had the same problem  In my case it arises  because the lookup-table  country  has an existing record with countryId  0 and a primitive primary key and I try to save a User with a countryID  0  Change the primary key of country to Integer  Now Hibernate can identify new records    For the recommendation of using wrapper classes as primary key see this stackoverflow question

User · Answer

You can t save things to Hibernate until you ve also told Hibernate about all the other objects referenced by this newly saved object   So in this case  you re telling Hibernate about a User  but haven t told it about the Country   You can solve problems like this in two ways    Manually  Call session save country  before you save the User   CascadeType  You can specify to Hibernate that this relationship should propagate some operations using CascadeType   In this case CascadeType PERSIST would do the job  as would CascadeType ALL     Referencing existing countries  Based on your response to  zerocool though  you have a second problem  which is that when you have two User objects with the same Country  you are not making sure it s the same Country   To do this  you have to get the appropriate Country from the database  set it on the new user  and then save the User   Then  both of your User objects will refer to the same Country  not just two Country instances that happen to have the same name   Review the Criteria API as one way of fetching existing instances

User · Answer

To add my 2 cents  I got this same issue when I m accidentally sending null as the ID  Below code depicts my scenario  and anyway OP didn t mention any specific scenario    Employee emp   new Employee    emp setDept new Dept deptId       ----- gt  when deptId PKID is null  same error will be thrown    calls to other setters    em persist emp     Here I m setting the existing department id to a new employee instance without actually getting the department entity first  as I don t want to another select query to fire   In some scenarios  deptId PKID is coming as null from calling method and I m getting the same error    So  watch for null values for PK ID  Same answer given here

User · Answer

Well if you have given    ManyToOne        JoinColumn  name    countryId      private Country country    then object of that class i mean Country need to be save first    because it will only allow User to get saved into the database if there is key available for the Country of that user for the same  means it will allow user to be saved if and only if that country is exist into the Country table   So for that you need to save that Country first into the table

User · Answer

It is because of CASCADE TYPE  if you put    OneToOne cascade CascadeType ALL   You can just save your object like this  user setCountry country   session save user    but if you put    OneToOne cascade                   CascadeType PERSIST              CascadeType REFRESH                       You need to save your object like this  user setCountry country   session save country  session save user

[java] Data was not saved: object references an unsaved transient instance - save the transient instance before flushing

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