How to render a domain and its relationships as JSON in Grails

Question

I'm trying to render a domain with its relationships as JSON in Grails 3.3.8.

I've already rendered a domain called Round that has many RoundItem and then I added another domain called AnswerOptions that belongs to RoundItem . How can I get that domain attributes from my controller to render all as JSON?

Here's the code:

Round:

class Round {
    String name
    String comments
    Date date
    Boolean enable

    static hasMany = [items: RoundItem, answers: RoundAnswer]
}

RoundItem:

class RoundItem {
    String name
    String comments
    String image
    String type

    static belongsTo = [round: Round]
    static hasMany = [items: RoundItem, answers: RoundAnswerItem, options: AnswerOption]
}

AnswerOption:

class AnswerOption {

    String option
    String type

    static belongsTo = [item: RoundItem]
}

Method of the controller where domains are rendered:

@Transactional  
def round(){  
    Round round = Round.get(params.id)  
    RoundItem roundItem = RoundItem.get(params.id)

    if(!checkEnableToRound(round)){  
        render status: METHOD_NOT_ALLOWED, text: '{"message":"Ya han tomado la prueba"}'  
        return  
    }  

    def items = []  
    round.items.each{  
        def item = [  
            id: it.id,  
            name: it.name,  
            comments: it.comments,  
            image: it.image,  
            answer: ''  
        ]  
        items.push(item)  
    }  

    Student student = springSecurityService.currentUser.student  
    RoundAnswer answer = RoundAnswer.findByRoundAndGroup(round,student.group)  
    if(!answer){  
        answer = new RoundAnswer(  
            round: round,  
            group: student.group,  
            userCreated: student.id,  
            userUpdated: student.id  
        )  
        answer.save(failOnError:true, flush:true)  
    }  

    def data = [  
        id: round.id,  
        name: round.name,  
        comments: round.comments,  
        items: items,  
        start: answer.dateCreated,  
        limit: checkLimit(answer.dateCreated)  
    ]  

    render data as JSON  
}

Answer 1

You can use gson plugin to create templates for rendering json output. It's the best practise to do that. More info here: http://views.grails.org/latest/