为什么我的JSONObject（String）返回空？

Question

So, I'm receiving from a post method a JSON, like that shown below (a JSON filled with arrays of strings). I receive it in my Java method as a string. My goal is to convert it to a JSONObject and to iterate about it, for example: x.getString("0")

But I have a problem, when I try to convert to a JSONObject, I am using import org.json.JSONObject , it returns an empty JSONObject like this : {} Why is it happening ? Thanks

EDIT: And the string is received with success because if I do return, it returns the JSON I've sent.

{ '0': [ 'Mon Apr 08 2019 19:26:37 GMT+0000 (UTC)' ],
  '1': [ '1234', '456', '1234', '456', '1234', '456', '545' ],
  '2': [ '1234', '456', '1234', '456', '1234', '456', '545' ],
  '3': [ '1234', '456', '1234', '456', '1234', '456', '545' ],
  '4': [ '1234', '456', '1234', '456', '1234', '456', '545' ],
  '5': [ 'Mon Apr 08 2019 19:30:00 GMT+0000 (UTC)' ] }

 // My Java method that converts JSON received to JSONObject:

@POST
    @Produces(MediaType.APPLICATION_JSON)
    @Path("/{nifCliente}") // irrelevant this part, ignore it, important is the String
    public JSONObject inserir (@PathParam("nifCliente")int c, String d) {
           JSONObject f = new JSONObject(d)
       return f;

    }

Answer 1

In your current implementation and JSON structure, in order to get the value, you should use f.get("0") and not f.getString("0"). Like this:

        String json = "{ '0': [ 'Mon Apr 08 2019 19:26:37 GMT+0000 (UTC)' ],\n" +
            "  '1': [ '1234', '456', '1234', '456', '1234', '456', '545' ],\n" +
            "  '2': [ '1234', '456', '1234', '456', '1234', '456', '545' ],\n" +
            "  '3': [ '1234', '456', '1234', '456', '1234', '456', '545' ],\n" +
            "  '4': [ '1234', '456', '1234', '456', '1234', '456', '545' ],\n" +
            "  '5': [ 'Mon Apr 08 2019 19:30:00 GMT+0000 (UTC)' ] }";
    JSONObject f = new JSONObject(json);
    System.out.println(f.get("0"));

The above code should work and the output will be:

["Mon Apr 08 2019 19:26:37 GMT+0000 (UTC)"]

Your JSOn is not valid. and you don't have the correct header of application/json in your postman collection. Try using this JSON:

{
"0": [
    "Mon Apr 08 2019 19:26:37 GMT+0000 (UTC)"
],
"1": [
    "1234",
    "456",
    "1234",
    "456",
    "1234",
    "456",
    "545"
],
"2": [
    "1234",
    "456",
    "1234",
    "456",
    "1234",
    "456",
    "545"
],
"3": [
    "1234",
    "456",
    "1234",
    "456",
    "1234",
    "456",
    "545"
],
"4": [
    "1234",
    "456",
    "1234",
    "456",
    "1234",
    "456",
    "545"
],
"5": [
    "Mon Apr 08 2019 19:30:00 GMT+0000 (UTC)"
]

}

EDIT 1:

And add the header to POSTMAN

Answer 2

Your problem is not in the construction of JSONObject, that works.

Your problem is that when you try to return that JSONObject as @Produces(MediaType.APPLICATION_JSON) the system doesn't know how to parse it.

You try to return the same object you receive and you will see how it works, because @Produces(MediaType.APPLICATION_JSON) knows parse String to Json.

Then try return f as string:

    @POST
    @Produces(MediaType.APPLICATION_JSON)
    @Path("/{nifCliente}") // irrelevant this part, ingore it, important is the String
    public String inserir (@PathParam("nifCliente")int c, String d) {
           JSONObject f = new JSONObject(d);

           return f.toString();

    }