CODEWITHSUNDEEP
javajsondictionary
user2442489
user2442489

Reputation:

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

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

Upvotes: 6

Views: 47155

Answers (5)

Arun Pratap Singh
Arun Pratap Singh

Reputation: 3666

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
        }

Upvotes: 1

jahroy
jahroy

Reputation: 22692

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)

Upvotes: 4

keelar
keelar

Reputation: 6026

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"
}}

Upvotes: 7

Ben
Ben

Reputation: 6059

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.

Upvotes: 2

Mayank Butpori
Mayank Butpori

Reputation: 17

I am assuming that you want to send a JSON back as a response to the calling request.. You could use the Spring framework where it automatically converts the Map object to JSON using Jackson converter. You will need to just use the annotation @ResponseBody for the return type. You can read more on the Spring 3 documentation.

Upvotes: 0

Related Questions