I know in grails i can define diferent JSON marshallers and asign names to them for different uses, which is very nice. However i end with a lot of code in the Bootstrap section and i end with two places where i need to tweak when domain classes changes.
Ithink thi is not good enough and i wonder if it might be possible to define JSON marshallers in the domain class itself.
Do you think would it be a good practice? ... can you provide suggestions on the best approach to achieve this?
Thanks,
I wrote a plugin for this purpose specifically. It allows you to use annotations in domain classes, like this:
import grails.plugins.jsonapis.JsonApi
class User {
static hasMany = [
pets: Pet
]
#JsonApi
String screenName
#JsonApi('userSettings')
String email
#JsonApi(['userSettings', 'detailedInformation', 'social'])
String twitterUsername
#JsonApi(['detailedInformation', 'userSettings'])
Set pets
String neverGetsSerialized
#JsonApi('detailedInformation')
Integer getNumberOfTicklyAnimals() {
pets.count { it.likesTickling }
}
}
In your controller, you would then call JSON.use('detailedInformation') to activate a specific marshaller.
In Bootstrap.groovy write this code:
JSON.registerObjectMarshaller(YourClass) { YourClass yourClass->
Map result = [:]
result['yourClass.property'] = yourClass.property
def domain = new DefaultGrailsDomainClass(YourClass)
domain.persistentProperties.each { GrailsDomainClassProperty property, String propertyName = property.name ->
result[propertyName] = yourClass[(propertyName)]
}
return result
}
Code below add one property, you can name it how u want
result['yourClass.property'] = yourClass.property
This code add all properties by it's name to map:
domain.persistentProperties.each { GrailsDomainClassProperty property, String propertyName = property.name ->
result[propertyName] = yourClass[(propertyName)]
}
Related
I have an enum with values
enum class Foo(val serverVal:Int) {
BAR(1),
BUG(2)
}
that I would like to use with a class:
data class C1(val fooVal:Foo)
I want to be able to serialise it with a code that looks as close as can be to:
Gson().toJson(C1(Foo.BAR))
That would yield
{"fooVal":1}
Instead of the default conversion, which is, of course {"fooVal":"BAR"}. If it was a string value I could have used #SerializedName, but I can't because it's an Int, not a String.
Is there a simple way to add something to Foo, in order to show Gson how to take the Int value from Foo entries rather than their name?
Examples I saw in Java include EnumAdapterFactory and TypeAdapter which are quite cumbersome and defeat the purpose of a pretty code.
I would love to get a solution that is maintained inside the data structure.
enum class SomeEnum(val i:Int) {
V1(1), V2(10), V3(5);
companion object {
#SerializeMeLikeThis
fun toJson() = i;
#DeserializeMeLikeThat
fun fromJson(v:Int) = values().find{it.i == v}?:whatever
}
}
An ugly way but still encapsulated-ish
data class C2(#SerializedName("foo") var serverFoo:Int) {
// Becomes a nightmare with many params.
constructor(f:Foo) : this(F.serverVal)
var foo:Foo
get() = Foo.values().find{serverFoo == it.serverVal}?:whatever
set(v) { serverFoo = v.serverVal }
}
So it can be called
Gson().toJson(C2(BAR))
and
// Result: Foo.BAR
Gson().fromJson("""{"foo":"1"}""", C2::class.java).foo
Well, you can live on it...but it... :-(
Any nice way?
Thanks
The Grails 2.5.4 docs say that it's possible to exclude properties from rendering for an entire group of domain classes.
There are some default configured renderers and the ability to register or override renderers for a given domain class or even for a collection of domain classes.
However there's no example given in the docs for how to do this. Does anyone know how to exclude properties for all of my domain classes? Specifically I'm trying to get rid of the class and enumType fields that Grails automatically adds to the response body.
There doesn't seem to be any good way to do this. What I discovered is that if you register an exclusion for a super class, all subclasses also "inherit" that exclusion. So to get rid of four properties for all Groovy objects (which cover all domain classes), I added the following bean to resources.groovy.
groovyObjectJsonRenderer(JsonRenderer, GroovyObject) {
excludes = ['class', 'declaringClass', 'errors', 'version']
}
I don't know if you are talking about this, but you can ignore some properties when you render as JSON, overriding the Marshaller here is the code:
static {
grails.converters.JSON.registerObjectMarshaller(NAMEOFYOURCLASS) {
return it.properties.findAll {k,v -> k != 'class' && k!='declaringClass'}
}
}
or if you want to create your custom render you can do something like this
static {
grails.converters.JSON.registerObjectMarshaller(NAMEOFYOURCLASS) {
def lista = [:]
lista['id'] = it.id
lista['name'] = it.name
lista['dateCreated'] = it.date?.format("dd/MM/yyyy HH:mm")
return lista
}
}
You can put it where you think its better i actually prefer to put it in the class i'm overriding, because letter i can find it or if some one else it's looking the code, he/she can find it easy.
The problem is as follows: I want to handle a POST request with JSON body. The body consists of an array of JSON Objects, without further nesting, i.e. simple HashMaps. All of these objects represent JSON-serialized domain classes from an Android Application, which will have their counterpart in my Grails app. I am thinking of parsing the JSON body, iterating through every element and saving each node as its corresponding domain class instance.
a) How should I save the instance? I am quite new to Grails/Groovy so please excuse any huge mistakes. Code so far is
public static Object JSONArray2Instances(String json, Class type) {
def slurper = new JsonSlurper()
def result = slurper.parseText(json)
//we only want to parse JSON Arrays
if (!(result instanceof JSONArray))
return null
result.each {
def instance = it.asType(type)
// now I need to save to domain class!
}
}
b) where do I place the corresponding code? Currently it is in /grails-app/src/groovy. Where do the tests go? (Since it is not a 'real' Grails component)
c) Is an intermediate command object more appropriate?
Your code should go in to the controller which is handling the request. Please take a look at
gson-grails plugin which has examples of how to serialize and deserialze objects and map them to domain objects. Please take a look at the grails basics where they talk about the conventions used in the grails application and the layout. There are good examples at grails site. Hope this helps
I solved my problem as follows, based on help provided by the comment from allthenutsandbolts. : (Grails-Gson plugin was not needed)
Let N2696AdminAction be the name of a Domain Class
in my controller:
class N2696AdminActionController extends RestfulController{
static responseFormats = ['json', 'xml']
def JSONHandlerService
N2696AdminActionController() {
super(N2696AdminAction)
}
#Override
#Transactional
def save(){
if (request!=null)
JSONHandlerService.instancesfromJSON(request.JSON)
}
}
then I delegate persisting to my service as follows
class JSONHandlerService {
def instancesfromJSON(Object request){
//we only want to parse JSON Arrays
if (!(request instanceof JSONArray))
return null
request.each {
def domainClass = Class.forName("${it.type}",
true, Thread.currentThread().getContextClassLoader())
def newDomainObject = domainClass.newInstance(it)
newDomainObject.save(failOnError:true, flush:true, insert: true)
}
}
}
type is a Json attribute which holds the full (package inclusive) name for my class. This way, I can save to multiple Domain Classes with the same POST request.
I would like to change the way enums are marshalled to JSON. I am currently using default grails.converters.JSON ( as JSON) and for example in controller I use:
FilmKind.values() as JSON
The output of this is:
"kind":[{"enumType":"FilmKind","name":"DRAMA"},{"enumType":"FilmKind","name":"ACTION"}]
I would like to remove "enumType" and just return:
"kind":["DRAMA","ACTION"]
I am looking for a solution which would still allow me to use
as JSON
because I don't want to marshall each enumeration individually.
In case anyone is wandering how to convert all enum values to plain String values in a generic way:
class EnumTypeHidingJSONMarshaller {
void register() {
JSON.registerObjectMarshaller(Enum) { Enum someEnum ->
someEnum.toString()
}
}
}
because I don't want to marshall each enumeration individually.
Well, unless you want to write your own JSON converter, marshalling is the best approach here. Reason is because the only real other way is to do what Sergio is suggesting and you'll have to call that code everywhere you need it. And if FilmKind is a property of another class then his solution won't work at all really.
I would suggest Marshallers and here is how I would do it. Create a class called FilmKindMarsaller:
class FilmKindMarshaller {
void register() {
JSON.registerObjectMarshaller(FilmKind) { FilmKind filmKind ->
[
name: filmKind.toString()
]
}
}
}
Then add the following to your Bootstrap:
[ new FilmKindMarshaller() ].each { it.register() }
The above is so that you can just keep adding instances of each Marshaller you need.
Now, anytime FilmKind is JSON'ified, be that on its own or part of a parent class, you get the JSON you want, sans enumType.
You can register a custom object marshaller for your domain class to allow as JSON. In your Bootstrap.groovy, you can do something like this:
JSON.registerObjectMarshaller(FilmKind) {
def result = [:]
def props = ['name']
props.each { prop ->
result[prop] = it."$prop"
}
result
}
How about:
def display = [kind:[]]
FilmKind.values().each { val ->
display.kind.add(val.value)
}
render display as JSON
Here is a Model
import org.bson.types.ObjectId
class Foo{
ObjectId id
String name
}
And here an action
def action = {
render(status:200, contentType:"application/json") {
['foo' : Foo.get(params.id)]
}
}
The action will return something like this
{"foo":{"class":"Foo","id":{"class":"org.bson.types.ObjectId","inc":340737392,"machine":-2019394572,"new":false,"time":1299107672000},"name":"fooName"]}
My question is, how can I send in the json the toString of the ObjectId, I don't want this
"id":{"class":"org.bson.types.ObjectId","inc":340737392,"machine":-2019394572,"new":false,"time":1299107672000}
I want something more like
"id":18893828183
I know I can select the parameters I want like:
def foo = Foo.get(params.id)
['foo' : 'Foo' :[id:foo.id.toString(), name:foo.name]]
But I don't want to declare always what I want to return as json, I want to return all the object, Foo.get(params.id).encodeAsJSON()...
Is there a way to override encodeAsJSON()
I already tried to add this
class Foo{
....
static transients : ['idStr']
def getIdStr(){
return this.id.toString()
}
....
}
But it's ignored in the encodeAsJSON()
I even tried this
class Foo{
....
def toJSON(){
def obj = this.encodeAsJSON()
def json = new JsonSlurper().parseText(obj);
json.idString = this.id.toString()
return json.toString()
}
...
}
this "works", but no....
because after this
render(status:200, contentType:"application/json") {
['foo' : Foo.get(params.id).toJSON()]
}
the render encode the json, so everything is "escaped"....
So what do you think is the solution, with a builder always defining what I want to return?
Hope, I made my question clear....
I'll start with the builder, hope you can give me another simpler / cleaner solution...
Thanks
edit
I just did a method that returns the object as a map so now I do something like this
render(status:200, contentType:"application/json") {
['foo' : getFooAsMap(Foo.get(params.id))]
}
Register this objectMarshaller at Bootstarp.groovy and it will work like a charm
import grails.converters.JSON
import org.bson.types.ObjectId
JSON.registerObjectMarshaller(ObjectId) {
return it.toStringMongod()
}
If you're going to be JSON-encoding your domain classes out to the web, I wonder if ObjectId might not be the best choice? The GORM/MongoDB integration allows you to use any type for the id. You could just declare it as a String type (which can be assigned as a toString of an ObjectId if you like to use that for its randomness) and then you don't need to worry about this mess. Any performance/scalability problems from this could be analysed/dealt with later, but I wouldn't expect there to be any unless it's a very large app.
Use GStrings in your map and you will get a numeric value for your ObjectId.
E.g.
render ["foo":"$foo.id"] as JSON
You can do this too:
def domainObj = YourDomainClass.get(params.id)
Map props = [:]
def domain = new DefaultGrailsDomainClass(YourDomainClass.class)
domain.properties.each{
props[it.name] = domainObj[it.name]
}
props["id"] = domainObj.id.toString()
render props as JSON
Or better yet, make it reusable. Put this closure someplace handy:
def mongoObjectResponse = {dobj ->
Map props = [:]
def domain = new DefaultGrailsDomainClass(YourDomainClass.class)
domain.properties.each{
props[it.name] = dobj[it.name]
}
props["id"] = dobj.id.toString()
// I like to leave room in my responses for messages and such
message = ""
obj = props
}
Then call like this from your controller:
return render(contentType: "text/json") {
mongoObjectResponse.delegate = delegate
mongoObjectResponse(domainObj)
}
Just define your domain class as
class Foo {
String id
String name
}
Instead of ObjectId