Grails, create domain object from json-string with has-many relation

Question

I'm trying to parse a grails parameter map to a Json String, and then back to a parameter map. (For saving html form entries with constraint-violations)

Everything is fine as long as there is no hasMany relationship in the parameter-map.

I'm using

fc.parameter = params as JSON

to save the params as JSON String.

Later I'm trying to rebuild the parameter map and create a new Domain-Object with it:

new Foo(JSON.parse(fc.parameter))

Everything is fine using only 1:1 relationships (states).

[states:2, listSize:50, name:TestFilter]

But when I try to rebuild a params-map with multi-select values (states)

[states:[1,2], listSize:50, name:TestFilter]

I'm getting this IllegalStateException:

Failed to convert property value of type org.codehaus.groovy.grails.web.json.JSONArray to required type java.util.Set for property states; nested exception is java.lang.IllegalStateException: Cannot convert value of type [java.lang.String] to required type [de.gotosec.approve.State] for property states[0]: no matching editors or conversion strategy found

I tried to use this, but without success:

JSON.use("deep") {
   new Foo(JSON.parse(fc.parameter))
}

Community · Accepted Answer · 2017-05-23 10:09:26Z

0

You can use JsonSlurper instead of the converters.JSON of grails, it maps JSON objects to Groovy Maps. I think this link also might help you.

Edit: Now, if the problem is binding the params map to your domain, you should try using bindData() method, like:

bindData(foo, params)

Note that this straightforward use is only if you're calling bindData inside a controller.

What seems to be happening in your case is that Grails is trying to bind a concrete type of List (ArrayList in the case of JsonSlurper and JSONArray in the case of converters.JSON) into a Set of properties (which is the default data structure for one-to-many associations). I would have to take a look at your code to confirm that. But, as you did substitute states: [1,2] for a method of your app, try another test to confirm this hypothesis. Change:

states:[1,2]

for

states:[1,2] as Set

If this is really the problem and not even bindData() works, take a look at this for a harder way to make it work using object marshalling and converters.JSON. I don't know if it's practical for you to use it in your project, but it sure works nicely ;)

edited May 23, 2017 at 10:09

CommunityBot

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answered Jul 9, 2012 at 18:24

Tiago Farias

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6 Comments

fabschu Over a year ago

Hi, using JsonSlurper, leadst to this exception: Failed to convert property value of type java.util.ArrayList to required type java.util.Set for property states; nested exception is java.lang.IllegalStateException: Cannot convert value of type [java.lang.String] to required type [de.gotosec.approve.State] for property states[0]: no matching editors or conversion strategy found --- why is the domain class required and not the id?

Tiago Farias Over a year ago

If you call the parse method from outside the object's constructor, you still get the same error? Or is it a object binding error?

fabschu Over a year ago

its an object binding error. The parsing makes no problem. it returns a Hashmap where states is an ArrayList and 1 and 2 Strings.

fabschu Over a year ago

If i replace the 'states:[1,2]' entry in the hashmap with State.getAll(map.get('states') as List<BigInteger>) everything is fine, but why do i have to do it. In the scaffolded save action the Domain Object is builded with the hash-map structure like 'states:[1,2]', why does it fail?

fabschu Over a year ago

Neither bindData nor the Set casting works, casting to Set leads to the Exception: Failed to convert property value of type java.util.HashSet to required type java.util.Set for property states; nested exception is java.lang.IllegalStateException: Cannot convert value of type [java.lang.Integer] to required type [de.gotosec.approve.State] for property states[0]: no matching editors or conversion strategy found

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