Styjun

I like google gson library.

When you don't know structure of json. You can use

JsonElement root = new JsonParser().parse(jsonString);

and then you can work with json. e.g. how to get "value1" from your gson:

String value1 = root.getAsJsonObject().get("data").getAsJsonObject().get("field1").getAsString();

Using the GSON library:

import com.google.gson.Gson;
import com.google.common.reflect.TypeToken;
import java.lang.reclect.Type;

Use the following code:

Type mapType = new TypeToken<Map<String, Map>>().getType(); 
Map<String, String[]> son = new Gson().fromJson(easyString, mapType);

Use JSON lib E.g. http://www.json.org/java/

// Assume you have a Map<String, String> in JSONObject jdata
@SuppressWarnings("unchecked")
Iterator<String> nameItr = jdata.keys();
Map<String, String> outMap = new HashMap<String, String>();
while(nameItr.hasNext()) 
 String name = nameItr.next();
 outMap.put(name, jdata.getString(name));

My post could be helpful for others, so imagine you have a map with a specific object in values, something like that:

 
 "shopping_list": 
 "996386": 
 "id":996386,
 "label":"My 1st shopping list",
 "current":true,
 "nb_reference":6
 ,
 "888540": 
 "id":888540,
 "label":"My 2nd shopping list",
 "current":false,
 "nb_reference":2
 
 

To parse this JSON file with GSON library, it's easy :
if your project is mavenized

<dependency>
 <groupId>com.google.code.gson</groupId>
 <artifactId>gson</artifactId>
 <version>2.3.1</version>
</dependency>

Then use this snippet :

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

//Read the JSON file
JsonElement root = new JsonParser().parse(new FileReader("/path/to/the/json/file/in/your/file/system.json"));

//Get the content of the first map
JsonObject object = root.getAsJsonObject().get("shopping_list").getAsJsonObject();

//Iterate over this map
Gson gson = new Gson();
for (Entry<String, JsonElement> entry : object.entrySet()) 
 ShoppingList shoppingList = gson.fromJson(entry.getValue(), ShoppingList.class);
 System.out.println(shoppingList.getLabel());

The corresponding POJO should be something like that :

public class ShoppingList 

 int id;

 String label;

 boolean current;

 int nb_reference;

 //Setters & Getters !!!!!

Hope it helps !

This way its works like a Map...

JSONObject fieldsJson = new JSONObject(json);
String value = fieldsJson.getString(key);

<dependency>
 <groupId>org.codehaus.jettison</groupId>
 <artifactId>jettison</artifactId>
 <version>1.1</version>
</dependency>

I do it this way. It's Simple.

import java.util.Map;
import org.json.JSONObject;
import com.google.gson.Gson;

public class Main 
 public static void main(String[] args) 
 JSONObject jsonObj = new JSONObject(" "f1":"v1"");
 @SuppressWarnings("unchecked")
 Map<String, String> map = new Gson().fromJson(jsonObj.toString(),Map.class);
 System.out.println(map);
 

java.lang.reflect.Type mapType = new TypeToken<Map<String, Object>>().getType();
Gson gson = new Gson();
Map<String, Object> categoryicons = gson.fromJson(json, mapType );

The JsonTools library is very complete. It can be found at Github.

With google's Gson 2.7 (probably earlier versions too, but I tested 2.7) it's as simple as:

Map map = gson.fromJson(json, Map.class);

Which returns a Map of type class com.google.gson.internal.LinkedTreeMap and works recursively on nested objects.

One more alternative is json-simple which can be found in Maven Central:

(JSONObject)JSONValue.parse(someString); //JSONObject is actually a Map.

The artifact is 24kbytes, doesn't have other runtime dependencies.

import net.sf.json.JSONObject

JSONObject.fromObject(yourJsonString).toMap

Underscore-java library can convert json string to hash map. I am the maintainer of the project.

Code example:

import com.github.underscore.lodash.U;
import java.util.*;

public class Main 

 @SuppressWarnings("unchecked")
 public static void main(String[] args) 
 String json = ""
 + " "data" :"
 + " "
 + " "field1" : "value1","
 + " "field2" : "value2""
 + " "
 + "";

 Map<String, Object> data = (Map) U.get((Map<String, Object>) U.fromJson(json), "data");
 System.out.println(data);

 // field1=value1, field2=value2
 

JSON to Map always gonna be a string/object data type. i haved GSON lib from google.

works very well and JDK 1.5 is the min requirement.