Retrieve values from JSON fields

Question

I tried to retrieve the parameter 'position' and its X and Y.

int npcId = reader.get("npcId").getAsInt();
int x = reader.get("position").getAsInt();
int y = reader.get("position").getAsInt();
int z = 0;

from this input, which is JSON

{
    "npcId": 414,
    "position": {
        "x": 3443,
        "y": 3536,
        "z": 0
    },
    "facing": "WEST",
    "radius": 13
}

For example int x = reader.get("position.X").getAsInt(); (Which obviously doesn't work but you get the idea.)

Probably something like `.get("position").get("x").getAsInt()` — Jonas Wilms, Jul 24 '18 at 11:10
@JonasW.: That question is not a proper dupe target of this one. If a question is tagged incorrectly, fix the tags. — Cerbrus, Jul 24 '18 at 11:12
@cerbrus six downvotes but no one flagged it. Dupe closing is way faster than voting as "unclear what you are asking" — Jonas Wilms, Jul 24 '18 at 11:14
After I edited the question, it is clear. I need to answer it, but now I cannot because the question is closed. — Yan Khonski, Jul 24 '18 at 11:14
@cerbrus I can't retract the close vote as you removed the js tag ... — Jonas Wilms, Jul 24 '18 at 11:15
@JonasW.: This question isn't unsalvageable. Dupe-hammering it for the sake of getting it closed by all means is abuse of your Mjölnir privilege. — Cerbrus, Jul 24 '18 at 11:15
@JonasW. But marking as a dupe won't be helpful to anyone who stumbles across this question in the future. If it gets closed by the normal fashion at least it would get roomba'd afterwards, not the case with dupes AFAIK — Michael Dodd, Jul 24 '18 at 11:15

Yan Khonski · Answer 1 · 2018-07-24T11:39:05.050

As I see from your post, you want to parse JSON input and retrieve values of some fields.

Here is an example, if you want to create a Java class corresponding to your JSON structure. Then you build an object from your JSON and retrieve the field directly. https://www.journaldev.com/2321/gson-example-tutorial-parse-json

Another way, which I did, is to build a map from your JSON, and iterate through it. In this case, you should know your JSON structure. This is an example, https://stackoverflow.com/a/12296567/4587961

1) Parse input String into a JSON object.

2) Iterate through the JSON object and find the fields you need.

3) Retrieve their values.

compile group: 'com.google.code.gson', name: 'gson', version: '2.8.5'

Gson gson = new Gson(); 
String json = "{\"k1\":\"v1\",\"k2\":\"v2\"}";//You input String
Map<String,Object> map = new HashMap<String,Object>();
//Check if map is not null and instance of Map.
map = (Map<String,Object>) gson.fromJson(json, map.getClass());
Object position = map.get("position");
//Check if position is not null and instance of Map. You can create a method to do this logic.
Map<String, Object> positionMap = (Map) position;
Object X = positionMap.get("x");
//Please, continue yourself.

Also you could use other libraries, for example, Jackson. This is your homework, try to learn more about JSON, and try different libraries, and a link to your github account with examples, so other people can also learn.

Thanks for your reply, this is my first post here and I don't quite understand how this website works =\ I still don't quite understand what you mean, It is JSON, If I post more code could you correct it for me ? Thank you. — Mike, Jul 24 '18 at 11:20
public static JsonLoader parse() { return new JsonLoader() { @Override public void load(JsonObject reader, Gson builder) { int npcId = reader.get("npcId").getAsInt(); int x = reader.get("position").getAsInt(); int y = reader.get("position").getAsInt(); int z = 0; if(reader.has("z")) { z = reader.get("z").getAsInt(); } //Spawn npc World.getNpcAddQueue().add(new NPC(npcId, new Position(x, y, z))); } — Mike, Jul 24 '18 at 11:21
@Mike if you feel like showing more code is helpful, kindly do so in your question. Not in comments. — kumesana, Jul 24 '18 at 11:29

Retrieve values from JSON fields

1 Answers1