Rapid Web Development with Grails - Learn Java for Web Development - page 343

Figure 7-31. Querying the table in H2
Creating Domain Relationships
In an application domain, classes have relationships to one another. The domain relationships define
how domain classes interact. Grails provides support for several types of relationships between domain
classes. A one-to-many relationship is when one class, Author , has many instances of the Book class.
With Grails you define such a relationship with the hasMany setting, as illustrated in Listing 7-31.
Listing 7-31. One-to-Many Relationship Between Author and Book
class Author {
static hasMany = [books: Book]
String name }
class Book {
String title
}