Java JSON Loading Returns Null

Question

I been working on this for way too long, I think I am just doing something stupid with GSON, not really sure. My debug indicates that it makes it to the map = builder.fromJson method but it still returns null.

Saving and Loading Methods

public static void saveTeleportData() {
    Path path = Paths.get("./data/definitions/teleports.json");
    File file = path.toFile();
    file.getParentFile().setWritable(true);

    if (!file.getParentFile().exists()) {
        try {
            file.getParentFile().mkdirs();
        } catch (SecurityException e) {
            System.out.println("Unable to create directory for Teleport data!");
        }
    }
    try (FileWriter writer = new FileWriter(file)) {

        Gson builder = new GsonBuilder().setPrettyPrinting().create();
        JsonObject object = new JsonObject();

        object.add("teleport-load", builder
                .toJsonTree(***Teleport Object Array***));

        writer.write(builder.toJson(object));
        writer.close();

    } catch (Exception e) {
        System.out.println("Failure");
    }
}

The saving method outputs this

https://pastebin.com/D5VpJXAj

So this looks right to me.

Heres the method that is called to load all of the 'Teleport' objects

public static Teleport[] loadTeleports() {

    // Create the path and file objects.
    Path path = Paths.get("./data/definitions/teleports.json");
    File file = path.toFile();

    // Now read the properties from the json parser.
    Teleport[] map = null;
    try (FileReader fileReader = new FileReader(file)) {
        JsonParser fileParser = new JsonParser();
        Gson builder = new GsonBuilder().create();
        JsonObject reader = (JsonObject) fileParser.parse(fileReader);

        if (reader.has("teleport-load")) {
            map = builder.fromJson("teleport-load", Teleport[].class);
            return map;
        }
    } catch (Exception e) {
        return null;
    }
    return map;
}

Also here is my Teleport Class, I am not sure what I could be doing wrong, all advice is appreciated! Let me know if you have any questions!

public class Teleport {

    private final String name;

    private final Position position;

    private final TeleportGroups teleGroup;

    public Teleport(String name, Position position, TeleportGroups teleGroup) {
        this.name = name;
        this.position = position;
        this.teleGroup = teleGroup;
    }

    public String getName() {
        return name;
    }

    public Position getPosition() {
        return position;
    }

    public TeleportGroups getTeleType() {
        return teleGroup;
    }

}

TL;DR - My loadTeleports method returns null even after I know its reading the file. GSON

Kirill Simonov · Accepted Answer · 2018-01-24 23:51:18Z

1

fromJson method expects a Reader, a JsonReader, a JsonElement, or a String with your actual JSON data as a first parameter, but you pass "teleport-load". Try to call it like this:

map = gson.fromJson(reader.get("teleport-load"), Teleport[].class);

In this case reader.get("teleport-load") will return a JsonElement representing the teleport-load property and then fromJson will convert it to a Teleport[] array.

edited Jan 24, 2018 at 23:51

answered Jan 24, 2018 at 23:39

Kirill Simonov

8,4913 gold badges23 silver badges47 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Eggspurt Over a year ago

Thanks Kirill! I used this same loading for other basic objects and it seemed to work, not sure why I had problems with this one. Thanks!

Collectives™ on Stack Overflow

Java JSON Loading Returns Null

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related