Implementing many to many relation between domains in Grails with MongoDB
Posted By : Shivam Gupta | 03-May-2014
As we know that implementation of many to many in sql is difficult because it needs a third table for maintaining relation. But it is easy in MongoDB , I will show you steps how to implement many to many relation in Grails with MongoDB
In a project, I had to implement many to many relation between two domains named as User and Circle. Scenario is that user has many circles and each circle has many user.
I assume that you have configured mongodb plugin in grails application and created database in mongodb.
Steps for implement many to many relation
Create two domain using following commands
grails create-domain-class User
grails create-domain-class Circle
Add data members and mapping
In User
String name;
List<Circle> circles
static mapWith = "mongo"
static hasMany=[circles:Circle]
In Circle
String name;
List<User> users;
static mapWith = "mongo"
static belongsTo=User //This line is used to make user as owner
static hasMany=[users:User]
After saving some documents in above domains you will see these domain like following manner in mongodb.
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About Author
Shivam Gupta
Shivam is a bright java developer with experience in building enterprise applications using Flex and Java. He is also well versed with Groovy and Grails development.