upickle: invalid string value during deserialization

Question

I am quite new in scala.js world so I decided to try it out on some small examples and one of them is quite simple get request with parsing of returning json back into scala entity.

Please find code which does it below:

def loadAndDisplayPosts(postsElement: Element) = {
  jQuery.get(
    url = "/posts",
    success = {
      (data: js.Any) =>
        val stringify = JSON.stringify(data)
        console.log(stringify)
        val posts = read[List[Post]](stringify)
        console.log(posts.size)
        posts.map(render).foreach(postsElement.appendChild)
    }
  )
}

console.log(stringify) returns the following json:

[
  {
    "title": "Some fancy title",
    "content": "some very long string with \"escaped\" characters",
    "tags": [
      "algorithms"
    ],
    "created": 1474606780004
  }
]

And when everything comes down to the

read[List[Post]](stringify)

I get the following exception:

upickle.Invalid$Data: String (data: 1474606780004)

So the question is: is anything there that is done wrong? Is there some valid reason for such behavior?

Version of library used:

"com.lihaoyi" %%% "upickle" % "0.4.1"

EDIT:

Adding entity itself:

case class Post(title: String,
                  content: String,
                  tags: List[String] = List.empty,
                  created: Long = System.currentTimeMillis())

EDIT 2:

The following code produces the same error:

val post = Post("Some title", "some \"content\"", List("algorithms"), 1474606780004L)
val json = write[List[Post]](List(post))

Thanks in advance for clarification.

I believe upickle serializes `Long`s as JSON strings. Try calling `write` on the manually instantiated list of posts and compare the output with your `stringify` string. — Jean-Philippe Pellet, Jun 07 '16 at 21:25
As an alternative: can you call `readJs` instead of `read`, passing `data` instead of `stringify`? — Jean-Philippe Pellet, Jun 07 '16 at 21:27
Changing callback signature to data: Js.Value and calling readJs method results this exception: scala.scalajs.runtime.UndefinedBehaviorError: An undefined behavior was detected: [object Object],[object Object],[object Object],[object Object],[object Object] is not an instance of upickle.Js$Value — tkachuko, Jun 07 '16 at 22:03
As I explained in EDIT 2, write did not succeed producing the very same error — tkachuko, Jun 08 '16 at 05:23

score 2 · Accepted Answer · edited May 23 '17 at 10:34

Well, actually the correct answer turned out to be here: upickle read from scalaJS - upickle.Invalid$Data: String (data: 1)

String is only partially correct answer. You can also use Double (at least you get free conversion from actual long for free on scala side).

So I ended up with the following entity which works just fine:

case class Post(title: String,
                  content: String,
                  tags: List[String] = List.empty,
                  created: Double = System.currentTimeMillis())

score 0 · Answer 2 · answered Jun 08 '16 at 19:17

0

uPickle serializes Longs as strings in JSON, because JavaScript numbers cannot represent all Longs.

Therefore, the created field of your object should be the string "1474606780004".

answered Jun 08 '16 at 19:17

sjrd

21,805
2
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Thanks for your reply. For me `created` is just a timestamp. Will uPickle be able to handle LocalDateTime from java 8 date/time API for example? – tkachuko Jun 08 '16 at 19:23
Also from uPickle web site: Out of the box, uPickle supports writing and reading the following types: Boolean, Byte, Char, Short, Int, **Long**, Float, Double. Why does it happen then that library is not able to work with case class that has `Long` field? – tkachuko Jun 08 '16 at 19:24
"uPickle serializes Longs as strings in JSON", - not true. `write[List[Post]](List(post))` produces the same exception so I would better say that it does not work with `Long` type at all. – tkachuko Jun 08 '16 at 19:28
should I create separate question regarding issue with `write` in `EDIT 2` of the original question or you will provide explanation in the same thread? – tkachuko Jun 08 '16 at 21:14
And also, when I do use jackson library to create json and native js to parse it, somehow I do not get this kind of problem ("JavaScript numbers cannot represent all Longs") – tkachuko Jun 09 '16 at 01:21

upickle: invalid string value during deserialization

2 Answers2