Strange validation conflict in Spring JPA TableGenerator - spring-boot

Question

I have a legacy database with composite primary key in table project. (BaseEntity contains common properties for lastModifiedDate and lastModifiedBy)
#Entity
#IdClass(ProjectPk.class)
public class Project extends BaseEntity {
#Id
#GeneratedValue(strategy=GenerationType.TABLE, generator="nextProjectId")
#TableGenerator(
name="nextProjectId",
table="projectId",
pkColumnName = "proj_Id",
pkColumnValue="proj_id"
)
private Long projId;
#Id
private int version;
//other properties, getters and setters omitted for clarity
}
PK class
public class ProjectPk implements java.io.Serializable {
private int projId;
private int version;
//both constructoirs, equals, hashcode, getters and setters omitted for clarity
}
I have flyway migration files to simulate production database.
drop table if exists project;
CREATE TABLE project
(
proj_id bigint,
version int,
-- other columns omitted for clarity
PRIMARY KEY (`proj_id`, `version`)
) ENGINE=InnoDB;
drop table if exists project_id;
CREATE TABLE project_id
(
proj_id bigint
) ENGINE=InnoDB;
flyway creates tables as ordered in migration file
Table: project_id
Columns:
proj_id bigint
...
Table: project
Columns:
proj_id bigint PK
version int PK
...
during maven build I'm getting validation error
Schema-validation: wrong column type encountered in column [proj_id] in table [project_id]; found [bigint (Types#BIGINT)], but expecting [varchar(255) (Types#VARCHAR)]
What I did wrong to make hibernate expect [varchar(255) (Types#VARCHAR)]?
This is SpringBoot project 2.6.6 with MySql database

Answer 1

I see the following problems with your code:
Type mismatch between Project.projId (Long type) and ProjectPk.projId (int type).
You use wrong table structure for the project_id table.
You can see a working example below.
Assuming that you have the following tables:
CREATE TABLE test_project
(
proj_id bigint,
version int,
title VARCHAR(50),
PRIMARY KEY (proj_id, version)
);
create table table_identifier (
table_name varchar(255) not null,
product_id bigint,
primary key (table_name)
);
insert into table_identifier values ('test_project', 20);
and the following mapping:
#Entity
#Table(name = "test_project")
#IdClass(ProjectPk.class)
public class Project {
#Id
#GeneratedValue(strategy = GenerationType.TABLE, generator = "nextProjectId")
#TableGenerator(
name="nextProjectId",
table="table_identifier",
pkColumnName = "table_name",
valueColumnName="product_id",
allocationSize = 5
)
#Column(name = "proj_id")
private Long projId;
#Id
private int version;
// other fields, getters, setters ...
}
you will be able to persist the entity like below:
Project project = new Project();
project.setVersion(1);
// ...
entityManager.persist(project);