Grails Object Relational Mapping (GORM)

Introduction

Domain classes are core to any business application. They hold state about business processes and hopefully also implement behavior. They are linked together through relationships, either one-to-one or one-to-many.

GORM is Grails' object relational mapping (ORM) implementation. Under the hood it uses Hibernate 3 (an extremely popular and flexible open source ORM solution) but because of the dynamic nature of Groovy, the fact that it supports both static and dynamic typing, and the convention of Grails there is less configuration involved in creating Grails domain classes.

You can also write Grails domain classes in Java. See the section on Hibernate Integration for how to write Grails domain classes in Java but still use dynamic persistent methods.

def book = Book.findByTitle("Groovy in Action")
book
  .addToAuthors(name:"Dierk Koenig")
  .addToAuthors(name:"Guillaume LaForge")
  .save()

More Information

• Creating a domain class
• Association & Composition
• Sets, Lists & Maps
• Mapping inheritance
• Performing CRUD operations
• Managing Relationships
• Domain Class Querying
• Custom ORM Mapping
• Automatic Timestamps & Events
• Hibernate Criteria Builder
• Using Gorm outside of Grails