Hibernate Save Or Update Return Id [TOP]
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How to Get the ID of a Saved or Updated Entity in Hibernate
Hibernate is a popular framework for object-relational mapping (ORM) that allows developers to work with Java objects and database tables in a convenient and efficient way. One of the common tasks that Hibernate users need to perform is to save or update an entity in the database and get its ID (primary key) value. In this article, we will explore how to do this using different methods of the Hibernate Session interface.
Using Session.save()
The save() method is used to make a transient (new) entity persistent by associating it with a Session. Before persisting the entity, it assigns a generated identifier to the ID field. The save() method returns the generated identifier so it has to immediately execute the SQL INSERT statement (it does not matter if we are inside or outside of a transaction) because identifiers are generated by the database during the INSERT query execution only[^2^].
For example, if we have an EmployeeEntity class mapped to an Employee table with an ID field as the primary key, we can use the save() method as follows:
```java
EmployeeEntity employee = new EmployeeEntity();
employee.setEmail(\"demo-user@email.com\");
employee.setFirstName(\"demo\");
employee.setLastName(\"user\");
Long id = session.save(employee); // returns the generated ID
```
This will execute the SQL INSERT statement and return the ID of the newly inserted record:
```sql
Hibernate: insert into Employee (ID, email, firstName, lastName) values (default, , , )
```
Using Session.update()
The update() method is used to reattach a detached (not associated with any Session) entity to a Session and update its state in the database. The update() method does not return anything, it returns void. However, we can get the ID of the updated entity from its getter method, assuming that it was already set when the entity was first persisted[^3^].
For example, if we have a detached EmployeeEntity instance with some modified fields, we can use the update() method as follows:
```java
EmployeeEntity employee = ...; // get a detached instance
employee.setLastName(\"userOne\"); // modify some fields
session.update(employee); // reattach and update
Long id = employee.getId(); // get the ID from the getter
```
This will execute the SQL UPDATE statement and return the ID of the updated record:
```sql
Hibernate: update Employee set lastName= where ID=
```
Using Session.saveOrUpdate()
The saveOrUpdate() method is used to either save a transient entity or update a detached entity, depending on whether it already has an identifier value or not. The saveOrUpdate() method does not return anything, it returns void. However, we can get the ID of the saved or updated entity from its getter method, similar to the update() method[^1^].
For example, if we have an EmployeeEntity instance that may or may not have an ID value, we can use the saveOrUpdate() method as follows:
```java
EmployeeEntity employee = ...; // get an instance
employee.setLastName(\"userTwo\"); // modify some fields
session.saveOrUpdate(employee); // save or update depending on ID
Long id = employee.getId(); // get the ID from the getter
```
This will execute either an SQL INSERT or UPDATE statement depending on whether the entity has an ID value or not:
```sql
Hibernate: insert into Employee (ID, email, firstName, lastName) values (default, , , )
-- or --
Hibernate: update Employee set lastName= where ID=
```
Conclusion
In this article, we learned how to get the ID of a saved or updated entity in Hibernate using different methods of the Session interface. We saw that the save() method returns the generated identifier directly, while the update() and saveOrUpdate() methods require us to use a getter method on the aa16f39245