Hibernate error: ids for this class must be manually assigned before calling save():

Hibernate error: ids for this class must be manually assigned before calling save():

The error message "ids for this class must be manually assigned before calling save()" in Hibernate typically occurs when you are trying to save an entity object, and the entity has an assigned identifier strategy (e.g., @Id with @GeneratedValue(strategy = GenerationType.IDENTITY) is not used), but you haven't assigned a value to its identifier property before calling save().

To resolve this issue, you need to ensure that you manually assign a valid identifier to your entity before saving it. Here are some steps to address this error:

  1. Ensure your entity class has an @Id annotation to specify the primary key property, and the identifier strategy is set to something other than GenerationType.IDENTITY. For example:

    @Entity
public class YourEntity {
    @Id
    private Long id;

    // Other entity properties and getters/setters
}

  2. Before calling save() or persist() to save your entity, you need to set a valid identifier value. You can do this by calling the setter method for the id property.

    YourEntity entity = new YourEntity();
entity.setId(1L); // Assign a valid identifier
// Set other properties as needed
session.save(entity); // Save the entity

  3. Make sure that you assign a unique and valid identifier value for each entity instance to avoid primary key conflicts.

If you want Hibernate to generate the primary key values automatically (e.g., using an auto-increment column in the database), then you should use the @GeneratedValue annotation with the appropriate strategy, such as GenerationType.IDENTITY. In this case, you don't need to manually assign identifier values, and Hibernate will take care of generating them.

Here's an example of using GenerationType.IDENTITY for an auto-generated primary key:

@Entity
public class YourEntity {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    // Other entity properties and getters/setters
}

By using GenerationType.IDENTITY, Hibernate will handle the assignment of primary key values when you save the entity, and you won't encounter the "ids for this class must be manually assigned before calling save()" error.

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