I finally figured out how to do this using a JSONBuilder
, here’s the code
import grails.web.*
class JSONSerializer {
def target
String getJSON() {
Closure jsonFormat = {
object = {
// Set the delegate of buildJSON to ensure that missing methods called thereby are routed to the JSONBuilder
buildJSON.delegate = delegate
buildJSON(target)
}
}
def json = new JSONBuilder().build(jsonFormat)
return json.toString(true)
}
private buildJSON = {obj ->
obj.properties.each {propName, propValue ->
if (!['class', 'metaClass'].contains(propName)) {
if (isSimple(propValue)) {
// It seems "propName = propValue" doesn't work when propName is dynamic so we need to
// set the property on the builder using this syntax instead
setProperty(propName, propValue)
} else {
// create a nested JSON object and recursively call this function to serialize it
Closure nestedObject = {
buildJSON(propValue)
}
setProperty(propName, nestedObject)
}
}
}
}
/**
* A simple object is one that can be set directly as the value of a JSON property, examples include strings,
* numbers, booleans, etc.
*
* @param propValue
* @return
*/
private boolean isSimple(propValue) {
// This is a bit simplistic as an object might very well be Serializable but have properties that we want
// to render in JSON as a nested object. If we run into this issue, replace the test below with an test
// for whether propValue is an instanceof Number, String, Boolean, Char, etc.
propValue instanceof Serializable || propValue == null
}
}
You can test this by pasting the code above along with the following into the grails console
// Define a class we'll use to test the builder
class Complex {
String name
def nest2 = new Expando(p1: 'val1', p2: 'val2')
def nest1 = new Expando(p1: 'val1', p2: 'val2')
}
// test the class
new JSONSerializer(target: new Complex()).getJSON()
It should generate the following output which stores the serialized instance of Complex
as the value of the object
property:
{"object": {
"nest2": {
"p2": "val2",
"p1": "val1"
},
"nest1": {
"p2": "val2",
"p1": "val1"
},
"name": null
}}