Get null property when trying to use JSON views on rest Controller just extending from RestfulController - rest

Question

I'm trying out JSON views, not on top of domain class using #Resource, but by creating a RestfulController and trying to render that using JSON views. I've added all the relevant dependencies in build config.
I have a domain Post class like this (which I didn't want to directly expose)
class Post implements Serializable {
Map comments
User user
Venue venue
String description
Rating rating //should this be an enum?
LocalDateTime dateCreated
LocalDateTime lastUpdated
static belongsTo = [user:User]
static hasOne = [rating:Rating]
static constraints = {
venue nullable:true
comments nullable:true
description nullable:true
rating nullable:true, lazy:false
}
static mapping = {
//set the sort order for Posts - default using newest post first
sort dateCreated :"desc"
}
}
So I then created a default RestfulController like this:
class PostRestController extends RestfulController {
static responseFormats = ["json", "xml"]
//constructor - tells rest controller which domain class to scaffold
PostRestController() {
super (Post)
}
}
I'm not overriding any of the default scaffolding methods here.
When I used a rest client to access the default (I've mapped /api/posts (resources: postRest in the UrlMappings). When I access the URL with my REST client I got the full dump of the Post (including comments field persisted in a map) - this looks like this in my rest client - all OK:
[
{
"id": 1,
"comments": {
"view": "lovely"
},
"dateCreated": {
"class": "java.time.LocalDateTime",
"dayOfMonth": 7,
"dayOfWeek": {
"enumType": "java.time.DayOfWeek",
"name": "TUESDAY"
},
"dayOfYear": 66,
"hour": 19,
"minute": 15,
"month": {
"enumType": "java.time.Month",
"name": "MARCH"
},
"monthValue": 3,
"nano": 263000000,
"second": 10,
"year": 2017,
"chronology": {
"calendarType": "iso8601",
"class": "java.time.chrono.IsoChronology",
"id": "ISO"
}
},
"description": null,
"lastUpdated": {
"class": "java.time.LocalDateTime",
"dayOfMonth": 7,
"dayOfWeek": {
"enumType": "java.time.DayOfWeek",
"name": "TUESDAY"
},
"dayOfYear": 66,
"hour": 19,
"minute": 15,
"month": {
"enumType": "java.time.Month",
"name": "MARCH"
},
"monthValue": 3,
"nano": 263000000,
"second": 10,
"year": 2017,
"chronology": {
"calendarType": "iso8601",
"class": "java.time.chrono.IsoChronology",
"id": "ISO"
}
},
"rating": null,
"user": {
"id": 1
},
"venue": null
}
],
I then tried to add JSON views on top of this in the grails-app/views/postRest folder.
I did a really simple template _post.gson like this:
model {
Post post
}
json {
comments post.comments
description post.description
//rating post.rating
userWhoPosted "${post?.user}"
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MMM-dd")
def when = post.dateCreated.format(formatter)
created when
}
I then added an index.gson to render the template:
model {
List<Post> postList
}
//call the template to iterate over the postList to produce the output
json g.render(postList)
This breaks the server with this stacktrace and a 500 error to the REST client. If I comment out the line in_post.gson relating to user it all works. Leave it in and it fails:
Caused by: grails.views.ViewRenderException: Error rendering view: null
at grails.views.AbstractWritableScript.writeTo(AbstractWritableScript.groovy:43)
at grails.views.mvc.GenericGroovyTemplateView.renderMergedOutputModel(GenericGroovyTemplateView.groovy:73)
at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:303)
at grails.views.mvc.renderer.DefaultViewRenderer.render(DefaultViewRenderer.groovy:111)
at grails.artefact.controller.RestResponder$Trait$Helper.internalRespond(RestResponder.groovy:188)
at grails.artefact.controller.RestResponder$Trait$Helper.respond(RestResponder.groovy:62)
at grails.rest.RestfulController.index(RestfulController.groovy:64)
at grails.transaction.GrailsTransactionTemplate$2.doInTransaction(GrailsTransactionTemplate.groovy:96)
at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:133)
at grails.transaction.GrailsTransactionTemplate.execute(GrailsTransactionTemplate.groovy:93)
... 4
If I comment out the post.user (and ratings reference) it works OK, but when I try and post the post.user it fails with the above. There was a note in the docs about ensuring that your query pulled the refs with a fetch join - so I tried to provide a override to ensure I returned the fetch join - all I get is empty returned to the client:
class PostRestController extends RestfulController {
static responseFormats = ["json", "xml"]
//constructor - tells rest controller which domain class to scaffold
PostRestController() {
super (Post)
}
def index() {
Collection<Post> res = Post.list([fetch:[user:"join",rating:"join"]])
res
}
}
Why when I do it without the JSON view it works fine and when I use the JSON view I can't get the output including references? I checked the list request and it returns the list successfully in the debugger - but breaks in the rendering.
If I can get this to work, JSON views on Grails 3.2.6 looks pretty nice.

Answer 1

Aaargh - think this issue is with jsonViews 1.1.5 - its not ready for java 8 LocalDateTime.
i saw a trace on stackoverflow see topic
hibernate will now take localdateTime in your domain classes - that works. But the json template rendering wont, even if you add the java8 plugin.
So i went back into domain class changed my LocalDateTime back to Date, also changed the json template to use the older SimpleDateTime format (instead of DateTimeFormatter) and re ran - low and behold it worked.
I'll be really glad when we can say grails is properly java8 ready.
apparently json views requires feature enablement which is due in json views 2 (think this is an M2 right now) - so i've had to revert to java 7 Date until then.
blimey another lost day in the weeds.