In Java, how to convert a String to JSON Object?

Question

The string is like so:

[{"Id":287,"Name":"aaaaaaaa","ProjectType":"GP"}, ... snip ...]

This STRING is not JSON yet since it is a string even though it was served up as JSON.

I am trying to convert that to a structure that I can work with in my Java app.

Can somebody help me out here. The examples I've found so far didn't work out for me. Basically, I was hoping to be able to iterate over the Dictionaries that are within the List.

My latest attempt to convert the string into a json, was this:

JSONObject data = new JSONObject(json_string);

This, however, returned null.

Thank you.

post your full string which u want to convert in json object — ρяσѕρєя K
– ρяσѕρєя K, Commented Dec 7, 2012 at 22:26
@JonathanGarcía that just means the object is an array, which is valid JSON AFAIK. — Frank van Puffelen
– Frank van Puffelen, Commented Dec 7, 2012 at 22:30
Then i believe that should use JSONArray, JSONObject of instead — Jonathan García
– Jonathan García, Commented Dec 7, 2012 at 22:39

chris-tulip · Accepted Answer · 2012-12-07 22:31:54Z

1

look at using the Gson Lib - it's very good at handling this sort of thing. If you implement it using generics you can create a set of serializers which would let you import data very nicely from mobile APIs. If you want more info on example implementations let me know

Source: http://code.google.com/p/google-gson/

documentation: https://sites.google.com/site/gson/gson-user-guide

answered Dec 7, 2012 at 22:31

chris-tulip

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digitaljoel · Accepted Answer · 2012-12-07 22:47:44Z

0

To go along with the Gson answer, I would suggest jackson. In my experience it's faster and just as easy to use.

ObjectMapper mapper = new ObjectMapper(); // can reuse, share globally
Map<String, Object> myMap = mapper.readValue(myJSONString, Map.class);

In your case, where the JSON is a list (I'm not sure if that's legal as the "root" element) you'd need to do List<Map<String, Object>> myList = mapper.readValue(myJSONString, List.class);

answered Dec 7, 2012 at 22:47

digitaljoel

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palako · Accepted Answer · 2012-12-07 23:52:08Z

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import com.google.gson.JsonArray;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;

JsonElement json = new JsonParser().parse("[{\"Id\":287,\"Name\":\"aaaaaaaa\",\"ProjectType\":\"GP\"}]");
        if(json.isJsonArray()) {        
            for(JsonElement elem : json.getAsJsonArray()) {
                //elem.getAsJsonObject().get("Id")
            }
        } else if (json.isJsonObject()) {
            //json.getAsJsonObject()
        } //other else cases for JsonNull, ...
    }

answered Dec 7, 2012 at 23:52

palako

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