i need to convert a POJO to a JSONObject (org.json.JSONObject)

I know how to convert it to a file:

 ObjectMapper mapper = new ObjectMapper(); try { mapper.writeValue(new File(file.toString()), registrationData); } catch (JsonGenerationException e) { e.printStackTrace(); } catch (JsonMappingException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); }

But I dont want a file this time.

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5 Answers

If we are parsing all model classes of server in GSON format then this is a best way to convert java object to JSONObject.In below code SampleObject is a java object which gets converted to the JSONObject.

SampleObject mSampleObject = new SampleObject(); String jsonInString = new Gson().toJson(mSampleObject); JSONObject mJSONObject = new JSONObject(jsonInString);
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If it's not a too complex object, you can do it yourself, without any libraries. Here is an example how:

public class DemoObject { private int mSomeInt; private String mSomeString; public DemoObject(int i, String s) { mSomeInt = i; mSomeString = s; } //... other stuff public JSONObject toJSON() { JSONObject jo = new JSONObject(); jo.put("integer", mSomeInt); jo.put("string", mSomeString); return jo; } }

In code:

DemoObject demo = new DemoObject(10, "string"); JSONObject jo = demo.toJSON();

Of course you can also use Google Gson for more complex stuff and a less cumbersome implementation if you don't mind the extra dependency.

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The example below was pretty much lifted from mkyongs tutorial. Instead of saving to a file you can just use the String json as a json representation of your POJO.

import java.io.FileWriter; import java.io.IOException; import com.google.gson.Gson; public class GsonExample { public static void main(String[] args) { YourObject obj = new YourOBject(); Gson gson = new Gson(); String json = gson.toJson(obj); //convert System.out.println(json); } }
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Here is an easy way to convert Java object to JSON Object (not Json String)

import com.fasterxml.jackson.databind.ObjectMapper; import org.json.simple.parser.JSONParser; JSONObject jsonObject = (JSONObject) JSONValue.parse(new ObjectMapper().writeValueAsString(JavaObject));
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How to get JsonElement from Object:

import com.fasterxml.jackson.databind.ObjectMapper; import com.google.gson.*; final ObjectMapper objectMapper = new ObjectMapper(); final Gson gson = new Gson(); String json = objectMapper.writeValueAsString(source); JsonElement result = gson.fromJson(json, JsonElement.class);