Merge (Concat) Multiple JSONObjects in Java

Question

I am consuming some JSON from two different sources, I end up with two JSONObjects and I'd like to combine them into one.

Data:

"Object1": {     "Stringkey":"StringVal",     "ArrayKey": [Data0, Data1] }  "Object2": {     "Stringkey":"StringVal",     "Stringkey":"StringVal",     "Stringkey":"StringVal", } 

Code, using http://json.org/java/ library:

// jso1 and jso2 are some JSONObjects already instantiated JSONObject Obj1 = (JSONObject) jso.get("Object1"); JSONObject Obj2 = (JSONObject) jso.get("Object2"); 

So in this situation I'd like to combine Obj1 and Obj2, either to make a totally new JSONObject or concat one to the other. Any ideas besides pulling them all apart and individually adding in by puts?

Answer 1

If you want a new object with two keys, Object1 and Object2, you can do:

JSONObject Obj1 = (JSONObject) jso1.get("Object1"); JSONObject Obj2 = (JSONObject) jso2.get("Object2"); JSONObject combined = new JSONObject(); combined.put("Object1", Obj1); combined.put("Object2", Obj2); 

If you want to merge them, so e.g. a top level object has 5 keys (Stringkey1, ArrayKey, StringKey2, StringKey3, StringKey4), I think you have to do that manually:

JSONObject merged = new JSONObject(Obj1, JSONObject.getNames(Obj1)); for(String key : JSONObject.getNames(Obj2)) {   merged.put(key, Obj2.get(key)); } 

This would be a lot easier if JSONObject implemented Map, and supported putAll.

Answer 2

In some cases you need a deep merge, i.e., merge the contents of fields with identical names (just like when copying folders in Windows). This function may be helpful:

/**  * Merge "source" into "target". If fields have equal name, merge them recursively.  * @return the merged object (target).  */ public static JSONObject deepMerge(JSONObject source, JSONObject target) throws JSONException {     for (String key: JSONObject.getNames(source)) {             Object value = source.get(key);             if (!target.has(key)) {                 // new value for "key":                 target.put(key, value);             } else {                 // existing value for "key" - recursively deep merge:                 if (value instanceof JSONObject) {                     JSONObject valueJson = (JSONObject)value;                     deepMerge(valueJson, target.getJSONObject(key));                 } else {                     target.put(key, value);                 }             }     }     return target; }    /**  * demo program  */ public static void main(String[] args) throws JSONException {     JSONObject a = new JSONObject("{offer: {issue1: value1}, accept: true}");     JSONObject b = new JSONObject("{offer: {issue2: value2}, reject: false}");     System.out.println(a+ " + " + b+" = "+JsonUtils.deepMerge(a,b));     // prints:     // {"accept":true,"offer":{"issue1":"value1"}} + {"reject":false,"offer":{"issue2":"value2"}} = {"reject":false,"accept":true,"offer":{"issue1":"value1","issue2":"value2"}} }