Json to Java

Convert a JSON string into a Java Map or Java List.

Make sure you have included all apache-commons, apache-logging, apache-discovery (and many other apache packaged required by json) and json-lib in your classpath

This class also has a small main function at the bottom, that shows how to use this class.
(Excuse me for the bad formatting, I will figure out how to update this post with a proper formatting.)

import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;

/**
*formatting a JSON response into Map and List
*/
public class Json2Java {
private static final int TIMEOUT = 5000; // 5 seconds timeout

//This is how you use it.
 public static void main(String a[]) throws Exception {
  Json2Java j = new Json2Java();
  String jsonStr = "{\"id\":101,\"person\":{\"fname\":\"foo\", \"lname\":\"bar\"}}";
  Map<String, Object> resp = j.getMap(jsonStr);
  System.out.println("Response message = " + ((Map)resp.get("person")).get("lname"));
}

/**
* getList provides a List representation of the JSON Object
* @param jsonResponse The JSON array string
* @return List of JSONObject.
**/
protected List<Object> getList(String jsonResponse) throws Exception {
  List<Object> listResponse = new ArrayList<Object>();
  if (jsonResponse.startsWith("[")) {
    JSONArray jsonArray = JSONArray.fromObject(jsonResponse);
    toJavaList(jsonArray, listResponse);
  } else {
    throw new Exception("MalFormed JSON Array Response.");
  }

  return listResponse;
}

/**
* getMap provides a Map representation of the JSON Object
* @param jsonResponse The JSON object string
* @return Map of JSONObject.
**/
protected Map<String, Object> getMap(String jsonResponse ) throws Exception {
  Map<String, Object> mapResponse = new HashMap<String, Object>();
  if (jsonResponse.startsWith("{")) {
    JSONObject jsonObj = JSONObject.fromObject(jsonResponse);
    toJavaMap(jsonObj, mapResponse);
  } else {
    throw new Exception("MalFormed JSON Array Response.");
  }
  return mapResponse;
}

/**
* toJavaMap converts the JSONObject into a Java Map
* @param o
* JSONObject to be converted to Java Map
* @param b
* Java Map to hold converted JSONObject response.
**/
private static void toJavaMap(JSONObject o, Map<String, Object> b) {
  Iterator ji = o.keys();
  while (ji.hasNext()) {
    String key = (String) ji.next();
    Object val = o.get(key);
    if (val.getClass() == JSONObject.class) {
      Map<String, Object> sub = new HashMap<String, Object>();
      toJavaMap((JSONObject) val, sub);
      b.put(key, sub);
    } else if (val.getClass() == JSONArray.class) {
      List<Object> l = new ArrayList<Object>();
      JSONArray arr = (JSONArray) val;
      for (int a = 0; a < arr.size(); a++) {
        Map<String, Object> sub = new HashMap<String, Object>();
        Object element = arr.get(a);
        if (element instanceof JSONObject) {
          toJavaMap((JSONObject) element, sub);
          l.add(sub);
        } else {
          l.add(element);
        }
      }
      b.put(key, l);
    } else {
      b.put(key, val);
    }
  }
}

/**
* toJavaList converts JSON's array response into Java's List
* @param ar
* JSONArray to be converted to Java List
* @param ll
* Java List to hold the converted JSONArray response
**/
private static void toJavaList(JSONArray ar, List<Object> ll) {
  int i = 0;
  while (i < ar.size()) {
    Object val = ar.get(i);
    if (val.getClass() == JSONObject.class) {
      Map<String, Object> sub = new HashMap<String, Object>();
      toJavaMap((JSONObject) val, sub);
      ll.add(sub);
    } else if (val.getClass() == JSONArray.class) {
      List<Object> l = new ArrayList<Object>();
      JSONArray arr = (JSONArray) val;
      for (int a = 0; a < arr.size(); a++) {
        Map<String, Object> sub = new HashMap<String, Object>();
        Object element = arr.get(a);
        if (element instanceof JSONObject) {
          toJavaMap((JSONObject) element, sub);
          ll.add(sub);
        } else {
          ll.add(element);
        }
      }
      l.add(l);
    } else {
      ll.add(val);
    }
    i++;
  }
}
}