I'm converting a list of Foo objects to a JSON string. I need to parse the JSON string back into a list of Foos. However in the following example, parsing gives me a list of JSONObjects instead of Foos.
Example
List list = [new Foo("first"), new Foo("second")]
def jsonString = (list as JSON).toString()
List parsedList = JSON.parse(jsonString) as List
println parsedList[0].getClass() // org.codehaus.groovy.grails.web.json.JSONObject
How can I parse it into Foos instead? Thanks in advance.
I had a look at the API docs for JSON and there doesn't appear to be any way to parse to a JSON string to a specific type of object.
So you'll just have to write the code yourself to convert each JSONObject
to a Foo
. Something like this should work:
import grails.converters.JSON
import org.codehaus.groovy.grails.web.json.*
class Foo {
def name
Foo(name) {
this.name = name
}
String toString() {
name
}
}
List list = [new Foo("first"), new Foo("second")]
def jsonString = (list as JSON).toString()
List parsedList = JSON.parse(jsonString)
// Convert from a list of JSONObject to a list of Foo
def foos = parsedList.collect {JSONObject jsonObject ->
new Foo(name: jsonObject.get("name"))
}
A more general solution would be to add a new static parse
method such as the following to the JSON
metaClass, that tries to parse the JSON string to a List of objects of a particular type:
import grails.converters.JSON
import org.codehaus.groovy.grails.web.json.*
class Foo {
def name
Foo(name) {
this.name = name
}
String toString() {
name
}
}
List list = [new Foo("first"), new Foo("second")]
def jsonString = (list as JSON).toString()
List parsedList = JSON.parse(jsonString)
// Define the new method
JSON.metaClass.static.parse = {String json, Class clazz ->
List jsonObjs = JSON.parse(json)
jsonObjs.collect {JSONObject jsonObj ->
// If the user hasn't provided a targetClass read the 'class' proprerty in the JSON to figure out which type to convert to
def targetClass = clazz ?: jsonObj.get('class') as Class
def targetInstance = targetClass.newInstance()
// Set the properties of targetInstance
jsonObj.entrySet().each {entry ->
if (entry.key != "class") {
targetInstance."$entry.key" = entry.value
}
}
targetInstance
}
}
// Try the new parse method
List<Foo> foos = JSON.parse(jsonString, Foo)
// Confirm it worked
assert foos.every {Foo foo -> foo.class == Foo && foo.name in ['first', 'second'] }
You can try out the code above in the groovy console. A few warnings
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