Grails/GORM 2.3 Hibernate looking for abstract domain class persisted table

Question

I'm new to Grails and GORM, but I have an old JPA2 (Hibernate) application on a legacy PostgreSQL to map, but I can't get inheritance of abstract classes to work, here is an example of the problem, let's use this tables:

users (id serial, username varchar, password char(44), user_modified integer, last_modified timestamp);
roles (id serial, role varchar, description varchar, enabled boolean, user_modified integer, last_modified timestamp);
permissions (user_id integer, role_id integer, enabled boolean);

As you can see the tables uses numeric auto-incremented id, but that's is not true for all of them, on the old JPA mappings I used a @MappedSuperclass to map the ID configurations, such as id generators, and some audit columns:

@MappedSuperclass
public abstract class DefId {
    @Id 
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    protected Long id;

    @NotNull 
    @Column(name = "user_modified")
    protected Long userModified;

    @Version 
    @Column(name = "last_modified") 
    @Source(SourceType.DB)
    protected Date lastModified;

    //getters and setters
}

Here is what I've tried so far in grails:

DefId.groovy:

abstract class DefId {
    /*In the actual source this are protected fields
    with public getters/setters removed for less code*/
    Long id; 
    Long userModified;
    Timestamp version;

    static mapping = {
        id generator: 'identity'
        version 'last_modified'
        userModified column: 'user_modified'
    }
}

User.groovy:

package maptest.domain

import maptest.model.DefId

class User extends DefId {
    String username
    String password
    boolean enabled
    static hasMany = [roles: Role];

    static mapping = {
        table name: "users", schema: "core"
        roles joinTable: [name: "permissions", key: "user_id"]
    }

    static constraints = {
        username blank: false, size: 2..20, matches: "^[A-Za-z]\\w+\$", unique: true
        password blank: false, matches: "^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?\$"
        preferences unique: true
    }
}

Role.groovy

package maptest.domain

import maptest.domain.DefId

class Role extends DefId{
    String role
    String description
    boolean enabled

    static hasMany = [users: User];
    static belongsTo = [User];

    static mapping = {
        table name: "roles", schema: "core"
        users joinTable: [name: "permissions", key: "role_id"]
    }
    static constraints = {
        role blank: false, size: 2..20, matches: "^[A-Za-z]\\w+\$", unique: true
        description   size: 2..50
    }
}

If I leave the abstract classes in the domain structure I got the exception: org.springframework.jdbc.BadSqlGrammarException: Hibernate operation: ERROR: relation "def_id" don't exists; that's is true, but I'm not trying to persist the abstract classes.

If I change the package and move the abstract class to src/groovy then I got: org.springframework.orm.hibernate4.HibernateSystemException: Unknown entity: mapetest.domain.User;

I also tried to add grails.gorm.default.mapping = { id generator: 'identity' } to the Config.groovy and remove the id field from superclass, but that only got me yet another error: Error loading plugin manager: Identity property not found, but required in domain class [maptest.domain.Role]

Anyone have any idea? Adding id generator: 'identity' ´ to every single domain class, solves it but that defeats the purpose of inheritance.

Excuse my english, it's a second language

Answer 1

Put your abstract class in the domain classes folder. You also need to tell Grails to consider a different table per class:

static mapping = {
  tablePerSubclass true
}

The default is only one table with a class column.

You also don't need to declare the id field, since it's auto generated by Grails, with the Long type.