Grails 3 JSON render can not render List?

Question

I have problem when rendering List result, is grails can not render list? here my code

def findSome(){
    String query = params?.some
    List<Some> someList = Some.createCriteria().list(max : 5) {
        if(query != null && query != ""){
            and {
                like("name", query)
            }
        }

        order("name", "asc")
    }
    someList = someList == null ? new ArrayList<Some>() : someList

    ->> render someList as JSON
}

there is something wrong with my code? what I remember is, grails CAN render List of object. but with this code, always return null in line with mark ->>.

What is the output of println someList before rendering ?

Prakash Thete
– Prakash Thete

2017-10-09 06:56:32 +00:00
Commented Oct 9, 2017 at 6:56 — Prakash Thete
– Prakash Thete, Commented Oct 9, 2017 at 6:56

BenHuman · Accepted Answer · 2017-10-27 17:54:22Z

6

Since the result you obtain from your criteria query is a list of objects, you should use render someList as JSONArray. In order to render as JSON, your list should have corresponding key value pair. You better convert the someList to a map of key-value pairs and render as JSON if you really want JSON object.

   def findSome(){
String query = params?.some
List<Some> someList = Some.createCriteria().list(max : 5) {
    if(query != null && query != ""){
        and {
            like("name", query)
        }
    }

    order("name", "asc")
}
someList = someList == null ? new ArrayList<Some>() : someList

render someList as JSONArray

}

if you want to render as JSON use the following code:

  def findSome(){
def someMap=[:]
String query = params?.some
List<Some> someList = Some.createCriteria().list(max : 5) {
    if(query != null && query != ""){
        and {
            like("name", query)
        }
    }

    order("name", "asc")
}
someList = someList == null ? new ArrayList<Some>() : someList
 someList.each{
   someMap.put(it.id,it) 
 }
 render someMap as JSON

}

answered Oct 27, 2017 at 17:54

BenHuman

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1 Comment

Thamer Over a year ago

could please give me the link of the documentation to this as JSON

marc_s · Accepted Answer · 2017-10-08 14:26:36Z

0

You should move the test for query outside of the criteria. No point creating it if query is nothing. You also don't need and in your criteria query, you can just use eq ("name", query)

In you're case the like and eq are the same.

edited Oct 8, 2017 at 14:26

marc_s

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answered Oct 7, 2017 at 21:34

grahamhumphries

1

1 Comment

dadang1234 Over a year ago

I have tried with what you said. with findAll() and I see the object is not null. but this controller always return null exception with there is [ in error view. I have no idea what happen with this JSON converters :|

Mario · Accepted Answer · 2017-10-08 14:30:23Z

0

Yes, grails can render object list. About your query, you could simplify to something like this.

def findSome() {
    respond Some.createCriteria().list {
        like 'name', "%$query%"

        maxResults 5
        order 'name', 'asc'
    }
}

If you are concerned that the query parameter is empty you can delegate that responsibility to command objects or url mappings constraints it depends on your case.

In the Responding with JSON section you can find other ways to respond to json

edited Oct 8, 2017 at 14:30

answered Oct 7, 2017 at 23:45

Mario

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7 Comments

dadang1234 Over a year ago

I think the error isn't at query. I have tried with findAll() and it return the same error :|

Mario Over a year ago

What grails version do you use?

dadang1234 Over a year ago

Grails Version: 3.2.8

Mario Over a year ago

you don need to depend on render someList as JSON you can try render(contentType: 'application/json') { someList } or respond someList, you can read about responding with JSON in this link docs.grails.org/latest/guide/single.html#jsonResponses. I updated my answer

dadang1234 Over a year ago

I have tried it. its return null. why the list is not null, but when it render as json the list become null :|

|

Ivan Pianetti · Accepted Answer · 2017-10-11 15:11:19Z

0

That happened to me only once and I solved it by forcing the response:

render(text: someList as JSON, contentType: 'application/json', encoding: 'UTF-8')

It's quite obvious, but make sure the method is inside a controller and it has this configuration:

static responseFormats = ['json', 'html']

answered Oct 11, 2017 at 15:11

Ivan Pianetti

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