Custom JSON marshalling

BootStrapSnip.groovy

// Custom marshalling
springContext.getBean( "customObjectMarshallers" ).register()

CustomObjectMarshallers.groovy

package util.marshalling

class CustomObjectMarshallers {

    List marshallers = []

    def register() {
        marshallers.each{ it.register() }
    }
}

RecipeMarshaller.groovy

package recipes

import grails.converters.JSON
import recipes.Recipe

class RecipeMarshaller {

    void register() {
        JSON.registerObjectMarshaller( Recipe) { Recipe recipe ->
            return [
                    id : recipe.id,
                    content : recipe.content,
                    userId : recipe.user.id,
                    username : recipe.user.username
            ]
        }
    }
}

resources.groovy

import util.CustomObjectMarshallers
import recipe.RecipeMarshaller

// Place your Spring DSL code here
beans = {
    customObjectMarshallers( CustomObjectMarshallers ) {
        marshallers = [
                new RecipeMarshaller()
        ]
    }
}

results.json

[
  {"id":1,"content":"foo foo bar bar","userId":"1","username":"joe"},
  {"id":2,"content":"woogie woogie whooo","userId":"1","username":"joe"}
]

snip1.groovy

render Recipe.list() as JSON

snip2.groovy

JSON.registerObjectMarshaller( Recipe ) { Recipe recipe ->
    return [
            id : recipe.id,
            content : recipe.content,
            userId : recipe.user.id,
            username : recipe.user.username
    ]
}