How to use createCriteria for many-to-many relation in Grails?

问题

I have domain classes as below:

class Account {
    String name
    String uniqueName
    static hasMany = [roles:Role]
}

class Role {
    String name
    static belongsTo = [account:Account]
    static hasMany = [users: User]
}

class User {
    String name
}

I received Account's uniqueName from params.uniqueName. And I want to find all users list that has roles that belongsTo account.

I want to use criteria() because I want to do it in pagination.

I try like below code, it's work but it can't do a pagination.

def account = Account.findByUniqueName(params.uniqueName)
def roles = account.roles
[users : roles.users.flatten().unique()]

How should I do this?

回答1:

Try this one: add to user:

static belongsTo = [role:Role]

and use this criteria:

User.createCriteria().listDistinct {
   role{
    account{
     eq("uniqueName", params.uniqueName)
    }
   }
}

回答2:

You can use criteria like this.

  List<Account> results =Account.createCriteria().list 
       { 
       eq('uniqueName', params.uniqueName) 
       maxResults(params.max as int)
       firstResult(params.offset as int)
       order(params.order, "asc")
       } 

回答3:

Try this:

Account account = Account.findByUniqueName(params.uniqueName)
Collection users = []

 account.roles.each{ role ->
  users += role.users
}

log.info("Users for ${params.uniqueName} account : ${users}"

来源：https://stackoverflow.com/questions/29360825/how-to-use-createcriteria-for-many-to-many-relation-in-grails