Converting JsonNode to java array

user_1304016 0
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I am working on Play framewrok 2 with websocket and JsonNode . the front end is connected to the play framework backend by use of websocket. I converted a javascript array into a json node and sent it to the backend by the use of the webscoket connection. Now my problem is how do i convert the json object into a a java array or any suitable structure so that i can manipulate the data.

this is the json object I created 

var myjeson = {"x":arrayX,"y":arrayY} ;

this is the array which is populated dynamically 

 function pixelCount ()
    {  arrayX[counter] = xcoordinate;        
    arrayY[counter] = ycoordinate;
    socket.send(" from array X,Y  "+arrayX[counter]+ " " +arrayY[counter]); 
    ++counter;      
    }

the code below sends the data 

$('button.send').click(function() {            
sock.send(JSON.stringify(myjeson));

on the server side i have the following code 

 public static WebSocket<JsonNode> givenIn() {
    return new WebSocket<JsonNode>() {
    // called when the websocket is established
    public void onReady(WebSocket.In<JsonNode> in, WebSocket.Out<JsonNode> out) {
    // register a callback for processing instream events             
    in.onMessage(new Callback<JsonNode>() {
    public void invoke(JsonNode event) {                 
    Logger.info(event.toString());
    }

when I check the log the message is delivered : below is the log info [info] application - 

{"x":
[78.72727298736572,79.72727298736572,82.72727298736572,
7298736572,93.72727298736572,83.72727298736572132.72727298736572],

"y":
[82.6363639831543,82.6363639831543,63.54545593261719,63.54545593261719,64.545455932
61719,65.54545593261719,70.54545593261719,189.5454559326172,188.5454559326172]}

Now I will like to place these data in an array so that I can access them. any suggestion will be appreciated.an alternative suggestion is also welcomed.

playframework-2.0 playframework json java
5 Answers

Moving my comment to an answer, as it got upvoted a lot.

This should do what the OP needed:

new ObjectMapper().convertValue(jsonNode, ArrayList.class)

user_12336610

"... how do I convert the json object into a java array"

import com.google.common.collect.Streams;

public void invoke(JsonNode event) {                 
    Streams.stream(event.withArray("x").elements())
        .forEach( num -> Logger.info(num.asDouble()) )
}

The trick is to first get the Iterator object using "elements()" method, then using Guava "stream" method get the stream. Once you have the stream you can do all kinds of array operations(e.g. filter, map) to consume your data.

user_25825810

Quick answer for the Tree Model approach mentioned by Stefano in the accepted answer:

JsonNode rootNode = new ObjectMapper().readTree(new StringReader(jsonStr));
JsonNode x=rootNode.get("x");
System.out.println(x.getNodeType());//should print: ARRAY
Iterator<JsonNode> arrayIterator=x.iterator();
List<Double> xList=new ArrayList<Double>();
while(arrayIterator.hasNext()) {
    JsonNode elementInX=arrayIterator.next();
    Double xDoubleValue=elementInX.asDouble();
    xList.add(xDoubleValue);
}
Double[] xArray=new Double[xList.size()];
xList.toArray(xArray);//xArray now should be what you want

//do the same thing to y
user_28301670
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