How to create unique constraint for 2 columns in JDL-Studio? - jhipster

Question

I have following entity configuration:
entity AirplaneModelSeat {
id Long,
seatNo String required
}
relationship ManyToOne {
AirplaneModelSeat{modelId(model)} to AirplaneModel
}
This entity configuration creates such a table:
+-------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+--------------+------+-----+---------+----------------+
| id | bigint(20) | NO | PRI | NULL | auto_increment |
| seat_no | varchar(255) | NO | | NULL | |
| model_id_id | bigint(20) | YES | MUL | NULL | |
+-------------+--------------+------+-----+---------+----------------+
How can I apply unique constraint for (seat_no, model_id_id) column combination in JDL-Studio?
If this is not possible in JDL-Studioi is there any other to accomplish this?

Answer 1

As far as I know, constraints are not part of JDL in a general manner. You can define such things as validations. But as for the Domain, the unique constraint is not that general anymore, it is a database level constraint, where it has to be applied.
For this, JHipster includes Liquibase. So you can find the changelog, defining the entity constraints in "src/main/resources/config/liquibase", and add a
<addUniqueConstraint tableName="airplane_model_seat" columnNames="seat_no, model_id_id"/>
to that changelog.
If you already started your application used h2 disk persistent databse, make a mvn clean / ./gradlew clean before starting your app again.

Answer 2

In addition to the Liquibase configuration in David's answer I suggest you also add the relevant JPA annotations to your Entity. Here is an example how:
#Table(name = "table_name",
uniqueConstraints = {#UniqueConstraint(columnNames = {"field_1", "field_2"})})
Note that since in this case #UniqueConstraint is applied at Entity (i.e. Table) level, you can combine multiple fields into a composite unique key.

Answer 3

In addition to Oerd's answer ^_^ In addition to the Liquibase configuration in David's answer I suggest you also add the relevant JPA annotations to your Entity.
If only To ensure a field value is unique you can write
#Column(unique=true)
String username;
The #UniqueConstraint annotation is for annotating multiple unique keys at the table level.
And also for Liquibase configuration, iff only To ensure a field value is unique you can write
<column name="username" type="varchar(255)">
<constraints nullable="true" unique="true" />
</column>