Reason for exception

[Navas Kc]

com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column 1 path $
at com.google.gson.Gson.fromJson(Gson.java:944)
at com.google.gson.Gson.fromJson(Gson.java:897)
at com.google.gson.Gson.fromJson(Gson.java:846)
at com.onedevice.admin.MainActivity$15.onResponse(MainActivity.java:886)
at com.onedevice.admin.RequestNetworkController$3$2.run(RequestNetworkController.java:179)
at android.os.Handler.handleCallback(Handler.java:790)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:192)
at android.app.ActivityThread.main(ActivityThread.java:6748)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:556)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:875)
Caused by: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column 1 path $
at com.google.gson.stream.JsonReader.beginObject(JsonReader.java:384)
at com.google.gson.internal.bind.MapTypeAdapterFactory$Adapter.read(MapTypeAdapterFactory.java:183)
at com.google.gson.internal.bind.MapTypeAdapterFactory$Adapter.read(MapTypeAdapterFactory.java:145)
at com.google.gson.Gson.fromJson(Gson.java:932)
... 11 more

[Campbell Ritchie]

Welcome to the Ranch

I am afraid we can't help from the information you have given us. Please supply lots more details. I have moved you to what I think is a more appropriate location. The stack trace mentioned Android, so I moved you to that forum; I don't know any Android myself.

[Paul Clapham]

My guess is that the JSON you're trying to process is badly formed. So that JSON should be included in the details you post next.

[Ron McLeod]

Paul Clapham wrote:My guess is that the JSON you're trying to process is badly formed.

I agree - the message Expected BEGIN_OBJECT but was STRING is telling you that something other than an opening curly-bracket was found when trying to parse an object.

class Person {
    String name;
}


@Test
void badJson() {
    var goodJson = """
            { "name" : "Jose" } """;
    parseAndPrint(goodJson);

    var badJson = """
            "name" : "Jose" """;
    parseAndPrint(badJson);

    var notJson = "Not JSON at all";
    parseAndPrint(notJson);
}

void parseAndPrint(String jsonStr) {
    System.out.println("attempting to parse: " + jsonStr);
    var gson = new Gson();
    try {
        var somePerson = gson.fromJson(jsonStr, Person.class);
        System.out.println("name is: " + somePerson.name);
    } catch (Exception e) {
        System.out.println(String.join(": ",
                e.getClass().getSimpleName(), e.getMessage()));
    }
    System.out.println();
}

attempting to parse: { "name" : "Jose" } name is: Jose attempting to parse: "name" : "Jose" JsonSyntaxException:    java.lang.IllegalStateException:    Expected BEGIN_OBJECT but was STRING at line 1 column 2 path $ attempting to parse: Not JSON at all    JsonSyntaxException: java.lang.IllegalStateException:    Expected BEGIN_OBJECT but was STRING at line 1 column 1 path $

[Ron McLeod]

If you are getting the content from a network endpoint:
  - check to the return status to ensure that the request was processed properly (for example - with HTTP: a 200 response)
  - ensure that the content type provided that the endpoint was as-expected (for example - with HTTP: Content-Type: application/json)
  - ensure that the content length is greater than zero

It would also be helpful to log the actual content so that you can visually inspect what was returned (or if more complex, copy/paste it in to an on-line JSON parser such as JSON Formatter.

[Rocky Raccoon]

Things to check quickly:
1. If you are using Gson, Kotlinx-serialization... basically, anything that is not the bad old JSONObject, make sure that it is configured to skip missing/redundant fields.
2. Did you try to just copy-paste your JSON to some JSON-lint site? https://jsonlint.com/ Note that when copy-pasting the JSON, Android Studio makes a mess with the quotes.
3. Alternatively, did you try to parse it with JSONObject(json) just to make sure it's legal.
That could be a hint.

Where do you go to from here?
1. If the JSON is legal, just make sure your parser can eat missing/redundant fields.
2. If not - the Achiles Heel is always the quotes. People forget to add them, or add them wrong.
3. If you are using KTOR or Retrofit - make sure that the headers are application/json. I've seen cases where it's fed wrong.