How to add two JSON formatted Java Strings together?

Question

I have two JSON Format Strings

 {"user1":{"Iden":4,"nID":1},"user2":{"Iden":5,"nID":1}} // String A JSON 

 {"user1":{"Iden":4,"nID":1},"user3":{"Iden":6,"nID":1},"user2":{"Iden":5,"nID":1}}

In the below program these above JSON are formatted by Eclipse IDE

This is my program:

import java.util.Map;

import org.codehaus.jackson.type.TypeReference;

import com.tradeking.at.util.JsonHelper;

public class Hi {
    private static JsonHelper jsonHelper = JsonHelper.getInstance();

    public static void main(String[] args) throws Exception {

        Map<String, Tracker> totalCusts = null;

        String A = "{\"user1\":{\"Iden\":4,\"nID\":1},\"user2\":{\"Iden\":5,\"nID\":1}}";
        String B = "{\"user1\":{\"Iden\":4,\"nID\":1},\"user3\":{\"Iden\":6,\"nID\":1},\"user2\":{\"Iden\":5,\"nID\":1}}";

        String totalString =  A+B;

        if (null != totalString) {
            totalCusts = (Map<String, Tracker>) jsonHelper.toObject(
                    totalString, new TypeReference<Map<String, Tracker>>() {
                    });

        }

        System.out.println(totalCusts);

    }

}

Tracker.java:

import org.json.JSONObject;

public class Tracker extends JSONObject{

}

When i ran the above , the Output is

{user1={}, user2={}}

if I use this:

String totalString =  B + A ;

The O/p is:

{user1={}, user3={}, user2={}}

Please let me know how I can add two JSON Strings??

B already contains all the contents of A so why are you concatenating it? — shyam
– shyam, Commented Nov 4, 2012 at 18:59

jbowes · Accepted Answer · 2012-11-04 19:00:13Z

5

At the top-level, a JSON document is always a single object, array, or value. By just concatenating the two strings together, you're violating this principal. A simple workaround would be to join the two values together in an array:

String totalString =  "[" + A + ", " + B + "]";

And then parse as such. Or you could simply parse each JSON document one at a time, and then append or merge your results (I suspect you want to merge them, via Map.putAll).

Given that the values for your userN keys are empty, you probably have a bug in your JsonHelper class, but that's hard to say without seeing the code.

answered Nov 4, 2012 at 19:00

jbowes

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