Grails GORM: How do I create a composite primary key and use it for a table relationship?

Question

I have two tables, one of which (legacy table: A) has two fields that should serve as a composite foreign key and the other one (new table: B) should use a composite primary key

Answer 1

import org.apache.commons.lang.builder.HashCodeBuilder
class Person implements Serializable {

String firstName
String lastName

boolean equals(other) {
    if (!(other instanceof Person)) {
        return false
    }

    other.firstName == firstName && other.lastName == lastName
}

int hashCode() {
    def builder = new HashCodeBuilder()
    builder.append firstName
    builder.append lastName
    builder.toHashCode()
}

static mapping = {
    id composite: ['firstName', 'lastName']
}
}

this is what you can find from official docs of grails,

http://grails.org/doc/latest/guide/GORM.html#compositePrimaryKeys

just blindly follow this and your problem will be solved. for explanation refer above link