Develop Reference

Gson serialize null values only when the field is in a nested object

The problem I am facing is that I want to ser/des null values when only it comes to non top-level attributes, and I have no idea how to achieve that. So let's say I have a User class:
Class User {
String name;
int id;
Address address;
}
And an Address class:
Class Address{
String street;
String city;
String country;
}
Right now, I can use below Gson instance to ser/des null values:
Gson gson = new GsonBuilder().serializeNulls().create();
Address address = new Address(null, "New York", "US");
User user = new User("Adam", 123, address);
String userJson = gson.toJson(user);
Output is:
{
"name": "Adam",
"id": 123,
"address": {
"street": null,
"city": "New York",
"country": "US"
}
}
However, I do NOT want to ser/des nulls when it comes to top-level attributes of User. For example for below User:
User user = new User("Adam", 123, null);
I want to have an output as below and without address field:
{
"name": "Adam",
"id": 123
}
I am now trying to use a customized serializer to hardcode every top-level attributes and remove them if they are null:
public class SerializerForUser implements JsonSerializer<ConfigSnapshot> {
#Override
public JsonElement serialize(User user, Type type, JsonSerializationContext jsc) {
Gson gson = new GsonBuilder().serializeNulls().create();
JsonObject jsonObject = gson.toJsonTree(user).getAsJsonObject();
if (user.getAddress() == null) {
jsonObject.remove("address");
}
// if... (same with other top-level attributes)
return jsonObject;
}
}
Gson gson = new GsonBuilder().serializeNulls().registerTypeAdapter(User.class, new SerializerForUser()).create();
But somehow it is not working, I will still get below output when for example address is null:
{
"name": "Adam",
"id": 123,
"address: null
}
can anyone give me some hints on what did I wrong here? Or it would be perfect if anyone can tell me if there is more straight forward/general way to achieve this(since I also want to use the same gson instance to ser/des other objects)?
Any comments are appreciated.

Because you are using
Gson gson = new GsonBuilder().serializeNulls().create();
which shows null value.
To skip showing null, let's try
Gson gson = new Gson();
You can test here
public static void main(String[] args) {
Gson yourGson = new GsonBuilder().serializeNulls().create(); // this is how you create your Gson object, which shows null value
Address address = new Address(null, "New York", "US");
User user = new User("Adam", 123, address);
String userJson = yourGson.toJson(user);
System.out.println(userJson);
Gson newGson = new Gson(); // with this one, it doesn't show value
System.out.println(newGson.toJson(user));
}
Update
I have tried to override the method serialize with a few times and it failed until I try #5
public class UserCustomSerializer implements JsonSerializer<User> {
#Override
public JsonElement serialize(User src, Type typeOfSrc, JsonSerializationContext context) {
JsonObject obj = new JsonObject();
if (src.name != null) {
obj.addProperty("name", src.name);
}
obj.addProperty("id", src.id);
if (src.address != null) {
// try #1
//JsonObject addressJsonObj = new JsonObject();
//addressJsonObj.addProperty("street", src.address.street != null ? src.address.street : null);
//addressJsonObj.addProperty("city", src.address.city != null ? src.address.city : null);
//addressJsonObj.addProperty("country", src.address.country != null ? src.address.country : null);
//obj.add("address", addressJsonObj);
// try #2
//Gson gson = new GsonBuilder().serializeNulls().create();
//JsonElement jsonElement = gson.toJsonTree(src.address);
//obj.add("address", jsonElement);
// try #3
//Gson gson2 = new GsonBuilder().serializeNulls().create();
//obj.addProperty("address", gson2.toJson(src.address));
// try #4
//Gson gson = new GsonBuilder().serializeNulls().create();
//JsonObject jsonObject = gson.toJsonTree(src.address).getAsJsonObject();
//obj.add("address", jsonObject);
// try #5
JsonObject addressJsonObj = new JsonObject();
addressJsonObj.addProperty("street", src.address.street != null ? src.address.street : "null");
addressJsonObj.addProperty("city", src.address.city != null ? src.address.city : "null");
addressJsonObj.addProperty("country", src.address.country != null ? src.address.country : "null");
obj.add("address", addressJsonObj);
}
return obj;
}
}
For try #3, I built the incorrect String.
For try #1, #2 and #4, I have the problem with the null value. I searched and found the reason and also the suggestion here
In a JSON "object" (aka dictionary), there are two ways to represent absent values: Either have no key/value pair at all, or have a key with the JSON value null.
So you either use .add with a proper value what will get translated to null when you build the JSON, or you don't have the .add call.
And my #5 approach is to check if the child node is null, I just add the string "null" literally and then I replace it when I build the json string
private String parseToGson(User user){
Gson gson = new GsonBuilder().registerTypeAdapter(User.class, new UserCustomSerializer()).create();
return gson.toJson(user).replace("\"null\"", "null");
}
Here are some test cases I defined
#Test
public void children_attribute_is_null() throws Exception {
String expected = "{\"name\":\"Adam\","
+ "\"id\":123,"
+ "\"address\":{"
+ "\""+ "street\":null,"
+ "\"city\":\"New York\","
+ "\"country\":\"US"
+ "\"}"
+ "}";
Address address = new Address(null, "New York", "US");
User user = new User("Adam", 123, address);
assertEquals(expected, parseToGson(user));
Gson g = new Gson();
User usr = g.fromJson( parseToGson(user), User.class);
assertEquals("Adam", usr.name);
assertEquals(123, usr.id);
assertEquals(null, usr.address.street);
assertEquals("New York", usr.address.city);
assertEquals("US", usr.address.country);
}
#Test
public void parent_attribute_is_null() throws Exception {
String expected = "{\"name\":\"Adam\","
+ "\"id\":123" + "}";
User user = new User("Adam", 123, null);
assertEquals(expected, parseToGson(user));
Gson g = new Gson();
User usr = g.fromJson( parseToGson(user), User.class);
assertEquals("Adam", usr.name);
assertEquals(123, usr.id);
assertEquals(null, usr.address);
}
#Test
public void parent_attribute_and_children_attribute_are_null() throws Exception {
String expected = "{\"id\":123,"
+ "\"address\":{"
+ "\"street\":null,"
+ "\"city\":\"New York\","
+ "\"country\":\"US"
+ "\"}"
+ "}";
Address address = new Address(null, "New York", "US");
User user = new User(null, 123, address);
assertEquals(expected, parseToGson(user));
Gson g = new Gson();
User usr = g.fromJson( parseToGson(user), User.class);
assertEquals(null, usr.name);
assertEquals(123, usr.id);
assertEquals(null, usr.address.street);
assertEquals("New York", usr.address.city);
assertEquals("US", usr.address.country);
}
Update #2
Since the previous version is not a generic one, I would like to update the answer.
For generic, I created MyCustomSerializer as following
public class MyCustomSerializer<T> implements JsonSerializer<T> {
private final Class<T> type;
public MyCustomSerializer(Class<T> type) {
this.type = type;
}
public Class<T> getMyType() {
return this.type;
}
#Override
public JsonElement serialize(T src, Type typeOfSrc, JsonSerializationContext context) {
JsonObject obj = new JsonObject();
try {
Field[] declaredFields = this.type.getDeclaredFields();
for (Field field : declaredFields) {
Object object = field.get(src);
if (object != null) {
// Here, we check for 4 types of JsonObject.addProperty
if (object instanceof String) {
obj.addProperty(field.getName(), (String) object);
continue;
}
if (object instanceof Number) {
obj.addProperty(field.getName(), (Number) object);
continue;
}
if (object instanceof Boolean) {
obj.addProperty(field.getName(), (Boolean) object);
continue;
}
if (object instanceof Character) {
obj.addProperty(field.getName(), (Character) object);
continue;
}
// This is where we check for other types
// The idea is if it is an object, we need to care its child object as well, so parse it into json string and replace the null value.
Gson gson = new GsonBuilder().serializeNulls().create();
String json = gson.toJson(object);
json = json.replace("null", "\"null\""); // We have to build the string first, then replace it with our special keys. In this case, I use the string "null"
JsonObject convertedObject = new Gson().fromJson(json, JsonObject.class); // Then convert it back to json object
obj.add(field.getName(), convertedObject);
}
}
} catch (IllegalAccessException e) {
e.printStackTrace();
}
return obj;
}
}
The main idea is still the same as previous version but I made it to a generic one.
I also added some additional properties to test for the string this code builds with the results
{
"id":123,
"address":{
"street":null,
"city":"New York",
"country":"US",
"info":{
"zipcode":null,
"address2":"stackoverflow",
"workPlaceAddress":{
"street":null,
"companyName":"google"
}
}
}
}
To call this, we need to do
private String parseToGson(User user) {
Gson gson = new GsonBuilder().registerTypeAdapter(User.class, new MyCustomSerializer<>(User.class)).create();
return gson.toJson(user).replace("\"null\"", "null");
}
Update #3
Since you still concern about your solution, I tried to adapt it as well
public class YourSerializer <T> implements JsonSerializer<T>{
private final Class<T> type;
public YourSerializer(Class<T> type) {
this.type = type;
}
public Class<T> getMyType() {
return this.type;
}
#Override
public JsonElement serialize(T src, Type typeOfSrc, JsonSerializationContext context) {
Gson gson = new GsonBuilder().serializeNulls().create();
JsonObject jsonObject = gson.toJsonTree(src).getAsJsonObject();
Field[] declaredFields = this.type.getDeclaredFields();
for (Field field : declaredFields) {
try {
if(field.get(src) == null) {
jsonObject.remove(field.getName());
}
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
return jsonObject;
}
}
The reason is you used serializeNulls() incorrectly which makes your output is incorrect. To correct it, you should registerTypeAdapter first to create your custom json, then you call serializeNulls
private String parseToGson(User user) {
Gson gson = new GsonBuilder().registerTypeAdapter(User.class, new YourSerializer<>(User.class)).serializeNulls().create();
return gson.toJson(user);
}
I tested and got the same result with update#2
{
"id":123,
"address":{
"street":null,
"city":"New York",
"country":"US",
"info":{
"zipcode":null,
"address2":"aaa",
"workPlaceAddress":{
"street":null,
"companyName":"google"
}
}
}
}

Get the key value from a json in Java - JSON Parsing

I have a json as below. I want to get mobile_number from this jsonObject.
json:-
{"id": "ABCD", "report": { "data": { "phone": { "mobile_number": 9876543210, "active": "Y", "content": null } } } }
I am doing it like this and it works fine but can someone help me with any other approach for it without getting every key.
JSONObject jsonObject = new JSONObject(json);
JSONObject report = getJSONObjectFromJson(jsonObject, "report");
JSONObject data = getJSONObjectFromJson(jsonObject, "data");
JSONObject phone = getJSONObjectFromJson(data, "phone");
long mobileNumber = getLongFromJson(phone, "mobile_number");
private Long getLongFromJson(JSONObject object, String key){
return (object !=null && object.has(key)) ? object.getLong(key) : null;
}
private JSONObject getJSONObjectFromJson(JSONObject object, String key){
return (object !=null && object.has(key)) ? object.getJSONObject(key) : null;
}

I've just dealing with the similar issue and decided to use JsonPath like this:
final DocumentContext jsonContext = JsonPath.parse(jsonString);
final Object read = jsonContext.read("$['report']['data']['phone']['mobile_number']");

You can use Jackson ObjectMapper.
try {
ObjectMapper mapper = new ObjectMapper();
String jsonString = "{\"id\": \"ABCD\", \"report\": { \"data\": { \"phone\": { \"mobile_number\": 9876543210, \"active\": \"Y\", \"content\": null } } } }";
JsonNode rootNode = mapper.readTree(jsonString);
JsonNode mobileNumber = rootNode.path("report").path("data").path("phone").path("mobile_number");
System.out.println("Mobile Number: " + mobileNumber.longValue());
} catch (JsonParseException e) {
e.printStackTrace();
} catch (JsonMappingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}

So there are lot of ways to do it but everything leads eventually to traversing the tree.
So to conclude all the approaches,
1. **Convert string to JsonObject and traverse.**
JSONObject jsonObject = new JSONObject(json);
JSONObject report = getJSONObjectFromJson(jsonObject, "report");
JSONObject data = getJSONObjectFromJson(jsonObject, "data");
JSONObject phone = getJSONObjectFromJson(data, "phone");
long mobileNumber = getLongFromJson(phone, "mobile_number");
private Long getLongFromJson(JSONObject object, String key){
return (object !=null && object.has(key)) ? object.getLong(key) : null;
}
private JSONObject getJSONObjectFromJson(JSONObject object, String key){
return (object !=null && object.has(key)) ? object.getJSONObject(key) : null;
}
2. **Using jackson objectMapper to get the JsonNode and then traverse.**
ObjectMapper mapper = new ObjectMapper();
JsonNode jsonNode= mapper.readTree(json);
JsonNode mobileNumber = jsonNode.path("report").path("data").path("phone").path("mobile_number");
3. **Using gson jsonmapper to convert to map and then iterate the map.**
Gson gson = new Gson();
Map map = gson.fromJson(json, Map.class);

jsonObject.getJSONObject("x").getJSONObject("Y").getJSONObject("z");
Another route would be to leverage the ObjectMapper.

How to extract the url of an image from a JSON (LastFM API)

I am a beginner in the use of JSON.
So I try to extract the url of an image from a JSON reply.
Here is the code that allows me to get an Array:
// Instantiate the RequestQueue.
RequestQueue queue = Volley.newRequestQueue(getActivity());
//String url ="http://www.google.com";
String url = "http://ws.audioscrobbler.com/2.0/?method=album.search&album="+albumName+"&api_key=c51f8eb36bad&format=json";
// Request a string response from the provided URL.
StringRequest stringRequest = new StringRequest(Request.Method.GET, url,
new Response.Listener<String>() {
#Override
public void onResponse(String response) {
// Display the first 500 characters of the response string.
//mTextView.setText("Response is: "+ response.substring(0,500));
Log.i("RESPONSE","Response is: "+ response);
JSONObject jsono = new JSONObject();
try {
jsono = new JSONObject(response);
//String url = jsono.getString("results");
//Log.i("RESPONSE",url);
} catch (JSONException e) {
e.printStackTrace();
Log.d ("RESPONSE",e.getMessage());
}
JSONArray jsonArray = new JSONArray();
try {
jsonArray = jsono.getJSONObject("results").getJSONObject("albummatches").getJSONArray("album");
} catch (JSONException e) {
e.printStackTrace();
Log.d ("RESPONSE",e.getMessage());
}
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject object = new JSONObject();
try {
object = jsonArray.getJSONObject(i);
Log.i("RESPONSE",object.getString("image"));
} catch (JSONException e) {
e.printStackTrace();
}
}
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
Log.i("RESPONSE","That didn't work!");
}
});
queue.add(stringRequest);
And here is the structure of this part in the JSON answer:
{
"album": [
{
"name": "DD Y Ponle Play",
"artist": "Jumbo",
"id": "2528039",
"url": "http://www.last.fm/music/Jumbo/DD+Y+Ponle+Play",
"image": [
{
"#text": "http://images.amazon.com/images/P/B00005LN6S.01._SCMZZZZZZZ_.jpg",
"size": "small"
},
{
"#text": "http://images.amazon.com/images/P/B00005LN6S.01._SCMZZZZZZZ_.jpg",
"size": "medium"
},
{
"#text": "http://images.amazon.com/images/P/B00005LN6S.01._SCMZZZZZZZ_.jpg",
"size": "large"
},
{
"#text": "http://images.amazon.com/images/P/B00005LN6S.01._SCMZZZZZZZ_.jpg",
"size": "extralarge"
}
]
}
]
}
How to get the url of an image for a given size?
Thank you very much for your suggestions.

You can use google GSON for this. Import it as a dependency
First create an album class.
public class Albums {
private List<Album> album;
public List<Album> getAlbum() {
return album;
}
public class Album{
private String name;
private String artist;
private String id;
private String url;
public String getName() {
return name;
}
public String getArtist() {
return artist;
}
public String getId() {
return id;
}
public String getUrl() {
return url;
}
public List<Image> getImage() {
return image;
}
public class Image {
#SerializedName("#text")
private String text;
private String size;
public String getText() {
return text;
}
public String getSize() {
return size;
}
}
private List<Image> image;
}
}
Now in your code where you get the above JSON object try this code below
Gson gson = new Gson();
// Im assuming "response" as the above JSON object
Albums albums = gson.fromJson(response.optString("album"),Albums.class);
This will map your json to java object.(Note: You can remove unwanted objects from the POJO as you like)
You can get the image using the getter functions

JSON is nothing but a key-value representation. It's not hard to get a hang of it. Your code should be something like this,
Update: This will only print URL's which have size = medium
String response = "{\"album\":[{\"name\":\"DD Y Ponle Play\",\"artist\":\"Jumbo\",\"id\":\"2528039\",\"url\":\"http://www.last.fm/music/Jumbo/DD+Y+Ponle+Play\",\"image\":[{\"#text\":\"http://images.amazon.com/images/P/B00005LN6S.01._SCMZZZZZZZ_.jpg\",\"size\":\"small\"},{\"#text\":\"http://images.amazon.com/images/P/B00005LN6S.01._SCMZZZZZZZ_.jpg\",\"size\":\"medium\"},{\"#text\":\"http://images.amazon.com/images/P/B00005LN6S.01._SCMZZZZZZZ_.jpg\",\"size\":\"large\"},{\"#text\":\"http://images.amazon.com/images/P/B00005LN6S.01._SCMZZZZZZZ_.jpg\",\"size\":\"extralarge\"}]}]}";
JSONObject myObject = new JSONObject(response);
JSONArray myArray = myObject.getJSONArray( "album" );
for(int i=0; i<myArray.length(); i++)
{
JSONObject myIterator = myArray.getJSONObject( i );
JSONArray arrayOne = myIterator.getJSONArray( "image" );
for(int j=0; j<arrayOne.length(); j++)
{
JSONObject myInnerIterator = arrayOne.getJSONObject( j );
if(myInnerIterator.has( "size" ))//check if 'size' key is present
if(myInnerIterator.getString( "size" ).equalsIgnoreCase( "medium" ))
System.out.println( myInnerIterator.getString( "#text" ) );
}
}

As mentioned by Raghunandan, you're extracting a JSONObject, when you need to be extracting a JSONArray, and then from that array, you can extract a JSONObject.
Try using a library such as GSON to make this task easier, or refer to this tiny JSON library I wrote.

It's pretty simple actually to parse a JSON array:
JSONArray jsonarray = new JSONArray("album");
for (int i = 0; i < jsonarray.length(); i++) {
JSONObject jsonobject = jsonarray.getJSONObject(i);
String url = jsonobject.getString("url");
}
Hope it helps!!!

To find the url of the images "medium" I did like this:
ArrayList<String> listUrl = new ArrayList<String>();
for(int i=0; i<jsonArray.length(); i++)
{
JSONObject myIterator = null;
try {
myIterator = jsonArray.getJSONObject( i );
JSONArray arrayOne = myIterator.getJSONArray( "image" );
for(int j=0; j<arrayOne.length(); j++)
{
JSONObject myInnerIterator = arrayOne.getJSONObject( j );
String s = myInnerIterator.getString( "size" )+myInnerIterator.getString("#text");
if (s.contains("medium") && s.contains("https")){
listUrl.add (s.replace("medium",""));
Log.i("RESPONSE",s.replace("medium",""));
}
}
} catch (JSONException e) {
e.printStackTrace();
}
I think there must be much better ... but it does the job!

Android: How to get JSON object keys from this json:

This is the JSON array:
{
"server_response": [{
"Total": "135",
"Paid": "105",
"Rest": "30"
}]
}
So, how can i get the object names? I want to put them in separate TextView.
Thanks.

Put this out side everything. I mean outside onCreate() and all.
private <T> Iterable<T> iterate(final Iterator<T> i){
return new Iterable<T>() {
#Override
public Iterator<T> iterator() {
return i;
}
};
}
For getting the names of objects :
try
{
JSONObject jsonObject = new JSONObject("{" +"\"server_response\": [{" +"\"Total\": \"135\"," +"\"Paid\": \"105\"," +"\"Rest\": \"30\"" +"}]"+"}";);
JSONArray jsonArray = jsonObject.getJSONArray("server_response");
JSONObject object = jsonArray.getJSONObject(0);
for (String key : iterate(object.keys()))
{
// here key will be containing your OBJECT NAME YOU CAN SET IT IN TEXTVIEW.
Toast.makeText(HomeActivity.this, ""+key, Toast.LENGTH_SHORT).show();
}
} catch (JSONException e) {
e.printStackTrace();
}
Hope this helps :)

My suggestion:
Go to this website:
Json to pojo
Get your pojo classes and then use them in Android.
All you need to do is to use Gson.fromGson(params here).
One of your params is the class that you created using the online schema.

You can use jackson ObjectMapper to do this.
public class ServerResponse {
#JsonProperty("Total")
private String total;
#JsonProperty("Paid")
private String paid;
#JsonProperty("Rest")
private String rest;
//getters and setters
//toString()
}
//Now convert json into ServerResponse object
ObjectMapper mapper = new ObjectMapper();
TypeReference<ServerResponse> serverResponse = new TypeReference<ServerResponse>() { };
Object object = mapper.readValue(jsonString, serverResponse);
if (object instanceof ServerResponse) {
return (ServerResponse) object;
}

JSONObject jsonObject = new JSONObject("Your JSON");
int Total = jsonObject.getJSONArray("server_response").getJSONObject(0).getInt("Total");
int Paid = jsonObject.getJSONArray("server_response").getJSONObject(0).getInt("Paid");
int Rest = jsonObject.getJSONArray("server_response").getJSONObject(0).getInt("Rest");

how to deserialize a json/gson that could be a string , object ,or list

I have the following json
"notes": {"note": [
{
"content": "Having wisdom teeth removed.",
"from": "employee"
},
{
"content": "Get well soon",
"from": "manager"
}
]},
the issue is that the value coud also be
"notes": "",
or
"notes": {"note": {
"content": "This is a test note.",
"from": "employee"
}},
and storing it in these
public class Notes
{
#SerializedName ("note")
public List<Note> note;
}
public class Note
{
#SerializedName ("content")
public String content;
#SerializedName ("from")
public String from;
}
I believe I solved the issue of not being an array but being an single object by doing this
public class Json {
private static Gson gson;
private static class MyNoteClassTypeAdapter implements JsonDeserializer<List<RequestsDTO.Note>> {
public List<RequestsDTO.Note> deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext ctx) {
List<RequestsDTO.Note> vals = new ArrayList<RequestsDTO.Note>();
if (json.isJsonArray()) {
for (JsonElement e : json.getAsJsonArray()) {
vals.add((RequestsDTO.Note) ctx.deserialize(e, RequestsDTO.Note.class));
}
} else if (json.isJsonObject()) {
vals.add((RequestsDTO.Note) ctx.deserialize(json,RequestsDTO.Note.class));
} else {
throw new RuntimeException("Unexpected JSON type: " + json.getClass());
}
return vals;
}
}
public static Gson getGson()
{
if (gson == null)
{
Type ListType = new TypeToken<List<RequestsDTO.Note>>() {}.getType();
GsonBuilder builder = new GsonBuilder();
builder.registerTypeAdapter(DateTime.class, new DateTimeSerializer());
builder.registerTypeAdapter(ListType, new MyNoteClassTypeAdapter());
gson = builder.create();
}
return gson;
}
}
And now I am stuck on when the whole thing just comes back as a string....

Refer the code snippet below to deserialize your json using Gson library without exceptions.
String jsonStr = "your json string ";
Gson gson = new Gson();
JsonObject jsonObj = gson.fromJson (jsonStr, JsonElement.class).getAsJsonObject();
JsonElement elem = jsonObj.get("note");
if(elem.isJsonArray()) { //**Array**
List<Note> notelist = gson.fromJson(elem.toString(), new TypeToken<List<Note>>(){}.getType());
} else if(elem.isJsonObject()) { //**Object**
Note note = gson.fromJson(elem.toString(), Note.class);
} else { //**String**
String note = elem.toString();
}

The idea is try to get "note" field (from "notes" JSONObject) as JSONArray first and if it throws exception that will mean that there is no "note" JSONArray into "notes" JSONObject and that will mean that "note" is JSONObject. The same way we can figure out situation when note field is String.
try {
//String jsonString="{\"notes\": {\"note\": [{\"content\": \"Having wisdom teeth removed.\",\"from\": \"employee\" }, {\"content\": \"Get well soon\", \"from\": \"manager\"} ] }}";
//String jsonString="{\"notes\": { \"note\": {\"content\": \"This is a test note.\",\"from\": \"employee\"}}}";
String jsonString="{\"notes\": { \"note\": \"\"}}";
JSONObject jsonObject=new JSONObject(jsonString);
JSONObject jsonObjectNotes=jsonObject.getJSONObject("notes");
try{
JSONArray jsonArrayNote=jsonObjectNotes.getJSONArray("note");
for (int i = 0; i < jsonArrayNote.length(); i++) {
JSONObject jsonObject2= jsonArrayNote.getJSONObject(i);
String stringContent=jsonObject2.getString( "content");
String stringFrom= jsonObject2.getString( "from");
Log.e(getClass().getName(), "content="+stringContent +"; from="+stringFrom);
}
}
catch(JSONException e){
//that means that jsonObjectNotes has no jsonArray with name "notes" and "notes" is jsonObject
try{
JSONObject jsonObject3=jsonObjectNotes.getJSONObject("note");
String stringContent=(String) jsonObject3.get( "content");
String stringFrom=(String) jsonObject3.get( "from");
Log.e(getClass().getName(), "content="+stringContent +"; from="+stringFrom);
}
catch(JSONException ex){
//that means that jsonObjectNotes has no jsonObject with name "notes" and "notes" is empty String
String stringNote=jsonObjectNotes.getString("note") ;
Log.e(getClass().getName(), "note is string ="+ stringNote);
}
}
} catch (JSONException e) {
e.printStackTrace();
}
In my example code another get operations can also throw jsonExceptions but I think you get the idea.

Have a look at Genson library http://code.google.com/p/genson/.
If your classes are inner classes make them static.
The following code should solve your problem.
Genson genson = new Genson.Builder().withDeserializerFactory(new NotesDeserializerFactory()).create();
Notes notes = genson.deserialize(in, Notes.class);
// Define a factory so you can delegate the deserialization to existing mechanisms for lists and beans
class NotesDeserializerFactory implements Factory<Deserializer<Notes>> {
#Override
public Deserializer<Notes> create(Type type, Genson genson) {
Converter<List<Note>> noteListConverter = genson.provideConverter(new GenericType<List<Note>>() {}.getType());
Converter<Note> noteConverter = genson.provideConverter(Note.class);
return new NotesDeserializer(noteListConverter, noteConverter);
}
}
// define an implementation for you Notes class so you can handle the different cases
class NotesDeserializer implements Deserializer<Notes> {
private final Converter<List<Note>> noteListConverter;
private final Converter<Note> noteConverter;
public NotesDeserializer(Converter<List<Note>> noteListConverter,
Converter<Note> noteConverter) {
this.noteListConverter = noteListConverter;
this.noteConverter = noteConverter;
}
#Override
public Notes deserialize(ObjectReader reader, Context ctx) throws TransformationException,
IOException {
Notes notes = new Notes();
if (reader.getValueType() == ValueType.ARRAY) notes.note = noteListConverter.deserialize(reader, ctx);
else if (reader.getValueType() == ValueType.OBJECT) notes.note = Arrays.asList(noteConverter.deserialize(reader, ctx));
else { // it is a litteral (string, numeric, boolean, null)
notes.note = new ArrayList<Note>();
}
return notes;
}
}