Want to read JSONArray with JSONObject, but got the error A non-empty JSON Pointer

Question

My Json FILE (it´s an array! )

[

{
    "datasetid": "country-flags",
    "recordid": "d661d0a8676bf4d7563114c1d9c465987df22132",
    "fields": {
        "num_un": 32,
        "geolocation": [
            -38.416097,
            -63.616672
        ],
        "dialing_code": "54",
        "a3_un": "ARG",
        "country": "Argentina",
        "flag": {
            "mimetype": "image/png",
            "format": "PNG",
            "filename": "ar.png",
            "width": 16,
            "id": "fceb4235ce95c8597bfa77d0db0181a0",
            "height": 11,
            "thumbnail": true
        },
        "a2_iso": "AR"
    },
    "geometry": {
        "type": "Point",
        "coordinates": [
            -63.616672,
            -38.416097
        ]
    },
    "record_timestamp": "2016-09-26T07:48:38.162+02:00"
},
more...

]

So i want to get the value from coordinates. So for this i tried to work with this:

    JsonReader jsonReader = Json
                .createReader(new FileReader(getClass().getResource("country-flags.json").getPath()));
        JsonArray arr = jsonReader.readArray();

        for(int i = 1; i<arr.size();i++)
        {
             JsonObject obj = arr.getJsonObject(i);
             System.out.println("coordinates: " + obj.containsKey("\"coordinates\""));

             System.out.println("##########");
             System.out.println(obj.getValue("\"coordinates\""));


        }

But i got the error:

javax.json.JsonException: A non-empty JSON Pointer must begin with a '/'

Can someone help me out ?!

What do you expect obj.getValue("\"coordinates\"") to do?

Savior
– Savior

2020-04-08 19:08:22 +00:00
Commented Apr 8, 2020 at 19:08 — Savior
– Savior, Commented Apr 8, 2020 at 19:08

Shrinath · Accepted Answer · 2020-04-08 19:25:57Z

2

Your code obj.containsKey("\"coordinates\"") will return false as coordinates is NOT a top level key, but is a 2nd level (nested) key. If you print obj.keySet(), you will get [datasetid, recordid, fields, geometry, record_timestamp] (first / top level keys only).

If the structure of your JSON is fixed, you can use the following code:

for(int i = 1; i<arr.size();i++)
{
     JsonObject obj = arr.getJsonObject(i);
     JsonObject jsonChildObject = obj.getJsonObject("geometry");
     if(jsonChildObject.containsKey("coordinates"))
          System.out.println(jsonChildObject.getValue("/coordinates"));
}

Notice the / in front of the getValue method's coordinates param. I think that was the reason you were here in the first place.

answered Apr 8, 2020 at 19:25

Shrinath

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2 Comments

user3515460 Over a year ago

Can you explain why i there is the leading "/" ?!

Shrinath Over a year ago

The leading "/" is the syntax as specified in the javadocs at javaee.github.io/javaee-spec/javadocs/javax/json/…. You can also check these two articles which explain the JSONPointer better. 1) baeldung.com/json-pointer 2) readlearncode.com/java-ee/… Hope that helps !

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