Kotlin: GSON fromJson doesn't compute - json

Question

I'm successfully receiving a JSON Object as request and passing it on to my parser. Code runs through until I call fromJson and then gets stuck. What am I doing wrong?
Here's the corresponding class:
class User(#SerializedName("mac") private val phoneMac: String) : Comparable<User> {
#SerializedName("values")
private val measurements: MutableSet<Measurement> = mutableSetOf()
fun getPhoneMac(): String = phoneMac
fun getMeasurements(): Set<Measurement> = measurements
//etc.
}
Which refers to this class:
class Measurement (#SerializedName("mac") val deviceMac: String, val timestamp: String, val value: Double, val valueType: ValueType) : Comparable<Measurement>{
fun getDeviceMac(): String = deviceMac
fun getTimestamp(): String = timestamp
fun getValue(): Double = value
fun getValueType(): ValueType = valueType
//etc.
}
And here is how I try to parse it:
fun fromJson(json: String): User {
val builder = GsonBuilder()
builder.setPrettyPrinting()
return builder.create().fromJson(json, User::class.java)
}
Had the fromJson-function spreaded out to make sure where it gets stuck: create() still works, fromJson() doesn't
Also, I know that the JSON file is correct and doesn't contain missing values or nulls.
For verification:
{
"mac": "00-80-41-ae-fd-b1",
"values":
[
{
"mac": "ab-cd-ef-98-76-13",
"timestamp": "2012-04-23T18:25:43",
"value": 68,
"valuetype": "HR"
},
{
"mac": "ab-cd-ef-98-76-13",
"timestamp": "2012-04-23T18:35:43",
"value": 65,
"valuetype": "HR"
}
]
}
Edit: for clarification as to what I mean with my code getting stuck
For debugging purposes, I changed my fromJson function to look like this:
fun fromJson(json: String): User {
val builder = GsonBuilder()
builder.setPrettyPrinting()
println("json received")
val gson = builder.create()
println("GSON created")
val user = gson.fromJson(json, User::class.java)
println("user created")
return user
}
My Console reads
json received
GSON created
Meaning "user created" is not printed, therefore the gson.fromJson-call never returns

Answer 1

Not sure what you mean by getting stuck, but this seems to work:
import com.google.gson.*
import com.google.gson.annotations.*
data class User(#SerializedName("mac") val phoneMac: String, #SerializedName("values") val measurements: MutableSet<Measurement>)
enum class ValueType{
HR
}
data class Measurement (#SerializedName("mac") val deviceMac: String, val timestamp: String, val value: Double, val valuetype: ValueType)
fun fromJson(json: String): User {
val builder = GsonBuilder()
builder.setPrettyPrinting()
return builder.create().fromJson(json, User::class.java)
}
fun main() {
println(fromJson("""
{
"mac": "00-80-41-ae-fd-b1",
"values":
[
{
"mac": "ab-cd-ef-98-76-13",
"timestamp": "2012-04-23T18:25:43",
"value": 68,
"valuetype": "HR"
},
{
"mac": "ab-cd-ef-98-76-13",
"timestamp": "2012-04-23T18:35:43",
"value": 65,
"valuetype": "HR"
}
]
}
""".trimIndent()))
}

Answer 2

It appears the fix was to get rid of getter functions in Measurement-class or setting the fields in Measurement-class private.
I copy/pasted barsju's code, and it worked. So step by step tried to swap in pieces of my code. After swapping in my Measurments-class, I got the following exception:
java.lang.ClassFormatError: Duplicate method name "getDeviceMac" with signature "()Ljava.lang.String;" in class file jsonStuff/Measurement
Did some experimentation and research only to find that if the fields of Measurement are not private but still have getter functions explicitly declared, they're recognized as duplicate functions, basically killing the application

Answer 3

I would suggest, if you can, use data classes, and remove the getters and the Comparable as well.
Also that's one of the differences of the example answers some of the users gave you here.