How to Generate IDs for Abstract Superclasses in Spring MVC Applications using Hibernate and MySQL?

@GeneratedValue Polymorphic Abstract Superclass over MySQL

When working with abstract superclasses and @GeneratedValue in a Spring MVC application using Hibernate and MySQL, it's essential to consider the specific requirements and limitations of the database. The error "Table 'docbd.hibernate_sequences' doesn't exist" often arises when GenerationType.TABLE is used with MySQL, which does not support sequences natively.

Problem Overview

The issue occurs because GenerationType.TABLE requires a table called "hibernate_sequences" to store the sequence values. Since MySQL does not have this table, Hibernate attempts to create it, resulting in the error. Additionally, using GenerationType.IDENTITY is not feasible when managing IDs in an abstract superclass.

Solution

Despite limitations with GenerationType.TABLE and GenerationType.IDENTITY, there is a solution that addresses both issues. Instead of relying on a sequence table or AUTO_INCREMENT, manually retrieving the next ID and setting it before saving the entity will resolve the problem. This approach involves the following steps:

1. Create a separate service method to generate new IDs.
2. Inside this method, retrieve the maximum ID value from the table corresponding to the entity being saved.
3. Increment the maximum ID by a predefined value (e.g., 1 or 100 for increased concurrency).
4. Return the generated ID.
5. In your DAO class, replace the @GeneratedValue annotation with a custom method call to retrieve the generated ID.
6. Set this generated ID using the setId() method on the entity before saving it.

This approach effectively generates new IDs without relying on sequences or AUTO_INCREMENT. It provides greater flexibility and ensures that the issue of non-existent sequences in MySQL is resolved.

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