Table Relationships

Defines relationships between tables, supporting OneToOne, ManyToOne, and ManyToMany in Exposed and Hibernate.

KtorAdmin supports three types of relationships between tables:

• One-to-One (OneToOne)

• Many-to-One (ManyToOne)

• Many-to-Many (ManyToMany)

OneToOne & ManyToOne

In Hibernate, OneToOne and ManyToOne relationships are automatically detected. These relationships are implemented in the same way.

Parameters:

• tableName → The name of the referenced table.

• foreignKey → The name of the foreign key column.

Example in Exposed:

@ManyToOneReferences("users", "id")
val userId = integer("user_id").references(Users.id)

@OneToOneReferences("users", "id")
val userId = integer("user_id").references(Users.id)

Note: The referenced tables must be registered with either ExposedTable or HibernateTable.

Example in Hibernate:

@ManyToOne
@JoinColumn(name = "author_id", nullable = false)
var author: Author

@OneToOne
@JoinColumn(name = "author_id", nullable = false)
var author: Author

ManyToMany

For ManyToMany relationships, use ManyToManyReferences.

Parameters:

• tableName → The name of the related table.

• joinTable → The name of the join table.

• leftPrimaryKey → The primary key column of the current table in the join table.

• rightPrimaryKey → The primary key column of the referenced table in the join table.

Example in Exposed:

@ManyToManyReferences"users", "tasks_users", "task_id", "user_id")
val users = EmptyColumn()

Note: EmptyColumn is designed specifically for Exposed. KtorAdmin recognizes it as a column in the admin panel. Any class that is not a subclass of Column in Exposed or EmptyColumn will not be detected.

Example in Hibernate:

@ManyToManyReferences("users", "tasks_users", "task_id", "user_id")
var users: List<User>

Displaying References in Forms

If you want to format how a reference is displayed in the edit or add page, you can use @DisplayFormat.

You can reference related columns using dot notation, like this:

@DisplayFormat(
    format = "{id} - User: {user_id.username}"
)
object Tasks : Table("tasks") {
    @IgnoreColumn
    val id = integer("id").autoIncrement()

    @ColumnInfo("user_id", verboseName = "Users")
    @OneToOneReferences("users", "id")
    val userId = integer("user_id").references(Users.id)
}

If a table references task, it will be displayed using the specified format in the admin panel. For example, if the format is {id} - User: {user_id.username}, a reference to a task with id = 5 and user_id.username = "JohnDoe" will appear as:

5 - User: JohnDoe