How to make a JSON String using the key/value from the Map

Question

I am trying to create a JSON String using the corresponding key/value pair. In the below code, I am trying to iterate the list of AttributeValue and then I am trying to makie the JSON String using the al.getValue map.

private <T> String createJsonWithEscCharacters(List<AttributeValue<T>> list) {

    StringBuilder keyValue = new StringBuilder();

    if (list != null) {
        for (AttributeValue<?> al: list) {

            keyValue.append("\"").append("v").append("\"").append(":").append(" {");

            for (Map.Entry<String, String> entry : ((Map<String, String>) al.getValue()).entrySet()) {
                keyValue.append("\"").append(entry.getKey()).append("\"");
                keyValue.append(":").append(" \"").append(entry.getValue()).append("\"").append(",");
                System.out.println(keyValue);
            }

        }
    }

    return null;
}

When I inspect on al, I see value as LinkedHashMap<K,V> and when I print al.getValue(), it gives me this-

{predictedCatRev=0;101;1,1;201;2, predictedOvrallRev=77;2,0;1,16;3, sitePrftblty=77;2,0;1671679, topByrGms=12345.67, usrCurncy=1, vbsTopByrGmb=167167.67}

So that means, I can iterate the al.getValue() map and use those key/value pair to make the JSON String.

Now I am trying to make a JSON String by iterating the al.getValue() map. So the JSON String should look something like this after iterating the al.getValue() map-

{
 "lv": [
  {
   "v": {
    "predictedCatRev": "0;101;1,1;201;2",
    "predictedOvrallRev": "77;2,0;1,16;3",
    "sitePrftblty": "77;2,0;1671679",
    "topByrGms": "12345.67",
    "usrCurncy": "1",
    "vbsTopByrGmb": "167167.67"
   }
  }
 ],
}

I am wondering what is the cleanest way to do this? In my above code, I am not fully able to make the above JSON String but whatever code I have above, it is able to make slight portion of JSON String in the way I needed but the not full JSON String in the way, I am looking for. Can anyone help me on this like what will be the cleanest way to do this?

Thanks

Solution 1

Not sure what exact task you're working, but there are many JSON libraries for Java which can do this for you such as json in java and google-gson. For example, in json in java, once you have filled all the values in its JSONObject, then converting it into JSON string is fairly easy:

JSONObject.toString();  // compact JSON string
JSONObject.toString(int indent);  // easier readable format with indention.

For example, in your case, you may create a JSONObject like the following and invoke its toString() function. This can safe your time from formatting string to fit the JSON format:

JSONObject jsonObject = new JSONObject();
Map<String, String> strStrMap = new HashMap<String, String>();

strStrMap.put("hello", "world");
strStrMap.put("here is", "an example");

jsonObject.put("myMap", strStrMap);

System.out.println(jsonObject.toString(2));

and here is its output:

{"myMap": {
  "hello": "world",
  "here is": "an example"
}}

Solution 2

You can just do something like this:

import org.json.JSONObject;

JSONObject rootJo = new JSONObject();

for (AttributeValue<?> al : list) {
    JSONObject mapJo = new JSONObject(al.getValue());
    rootJo.put("v", mapJo);
}

In other words:

• create a new (empty) JSONObject named rootJo (root JSON object)
• iterate over your list of maps
• for each element in the list, convert the map into a JSONObject (using a library)
• add a new property to rootJo (the key will be v)
• set the value of v to the JSONObject that was created from the map

Maybe I'm missing something, but I would replace your entire method with this:

/**
 *  Creates a JSON object from a list of attributes that
 *  have maps as their values.
 */

private JSONObject toJson(List<AttributeValue<?>> attList) {
    if (attList == null) {
        return null;
    }
    JSONObject jo = new JSONObject();
    JSONArray  ja = new JSONArray();
    for (AttributeValue<?> att : attList) {
        JSONObject mapJo = new JSONObject(att.getValue());
        ja.put("v", mapJo);
    }
    jo.put("lv", ja);
    return jo;
}

You should also make it typesafe, but I'll leave the finer details to you...

(plus I'm not sure what an AttributeValue is... can't find it anywhere)

Solution 3

Use Jackson. It's lightweight and faster than Gson. It also isn't known to be bundled by OEMs, which can mess with your classpath.

Solution 4

When using google gson.

var getRowData =
[{
    "dayOfWeek": "Sun",
    "date": "11-Mar-2012",
    "los": "1",
    "specialEvent": "",
    "lrv": "0"
},
{
    "dayOfWeek": "Mon",
    "date": "",
    "los": "2",
    "specialEvent": "",
    "lrv": "0.16"
}];

    JsonElement root = new JsonParser().parse(request.getParameter("getRowData"));
     JsonArray  jsonArray = root.getAsJsonArray();
     JsonObject  jsonObject1 = jsonArray.get(0).getAsJsonObject();
     String dayOfWeek = jsonObject1.get("dayOfWeek").toString();

// when using jackson

    JsonFactory f = new JsonFactory();
              ObjectMapper mapper = new ObjectMapper();
          JsonParser jp = f.createJsonParser(getRowData);
          // advance stream to START_ARRAY first:
          jp.nextToken();
          // and then each time, advance to opening START_OBJECT
         while (jp.nextToken() == JsonToken.START_OBJECT) {
            Map<String,Object> userData = mapper.readValue(jp, Map.class);
            userData.get("dayOfWeek");
            // process
           // after binding, stream points to closing END_OBJECT
        }

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