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Serialize to JSON as name-value from String by Jackson ObjectMapper

I have some String, like:
String value = "123";
And when i serialize this string to json via ObjectMapper:
objectMapper.writeValueAsString(value);
Output is:
"123"
Is it possible to write String using either string name and string value? Desired output:
"value" : "123"
PS: i dont want to create DTO object with one field for serializing one String value.

you can also use the Jackson JsonGenerator
try (JsonGenerator generator = new JsonFactory().createGenerator(writer)) {
generator.writeStartObject();
generator.writeFieldName("value");
generator.writeString("123");
generator.writeEndObject();
}
}

If you have a plain string you'll get out a plain string when serialised. If you want to wrap it in an object then use a map for the simplest solution.
String value = "123";
Map<String, String> obj = new HashMap<>();
obj.put("value", value);
Passing that through the mapper will produce something like this:
{ "value": "123" }
If you change the map to <String, Object> you can pass in pretty much anything you want, even maps within maps and they'll serialise correctly.
If you really can't have the enclosing curly braces you can always take the substring but that would be a very weird use case if you're still serialising to JSON.

Create a Map:
Map<String, String> map = new HashMap<>();
map.put("value", value);
String parsedValue = ObjectMapper.writeValueAsString(map);
and you will get: {"value":"123"}

If you are using java 8 and want to do it in automated way without creating maps or manually putting string variable name "value", this is the link you need to follow-

Mapping JSON with varying object name

I'm quite new to JSON, and I've looked around trying to work out what to do but not sure if I fully understand. I am making an external API call returning:
2015-12-21 01:22:09 INFO RiotURLSender:60 - Total json:
{"USERNAME":{"profileIconId":984,"revisionDate":1450655430000,"name":"USERNAME2","id":38584682,"summonerLevel":30}}
Where 'USERNAME' (And USERNAME2 - which can be very slightly different to USERNAME) will vary depending on what you pass the call's parameters. I was using Jackson Object Mapper to map the individual values within the USERNAME object - but didn't realise I had to map the object as well.
I've been using annotations in the DTOs like:
#JsonProperty("profileIconId")
private Long profileIconId;
and mapping using:
summonerRankedInfoDTO = mapper.readValue(jsonString, SummonerRankedInfoDTO.class);
How do I map using a value of USERNAME which is changing every single time?
Also this seems a bit odd, is this bad practice to have the actual varying key rather than just have the same key and different value?
Thanks

you can use following mentioned annotation #JsonAnyGetter And #JsonAnySetter.
Add this code into ur domain class. So any non-mapped attribute will get populated into "nonMappedAttributes" map while serializing and deserializing the Object.
#JsonIgnore
protected Map<String, Object> nonMappedAttributes;
#JsonAnyGetter
public Map<String, Object> getNonMappedAttributes() {
return nonMappedAttributes;
}
#JsonAnySetter
public void setNonMappedAttributes(String key, Object value) {
if (nonMappedAttributes == null) {
nonMappedAttributes = new HashMap<String, Object>();
}
if (key != null) {
if (value != null) {
nonMappedAttributes.put(key, value);
} else {
nonMappedAttributes.remove(key);
}
}
}

You should try to keep the keys the exact same if possible and change values, otherwise you'll have to change your JSON. Since JSON returns a value from the key, the value can change to anything it wants, but you'll be able to return it from the key. This doesn't work the other way around though.
Anyway to your question, you may have a little better luck using something like the GSON library, its pretty simple to use.
You can create the instance and pass it the JSON string:
Gson gson = new Gson();
JsonObject obj = gson.fromJson(JSON_DOCUMENT, JsonObject.class);
Then you can get certain elements from that now parsed JSON object.
For example, in your JSON string, username returns another JSON element, so you can do:
JsonObject username = obj.get("USERNAME").getAsJsonObject();
Then just repeat the same steps from there to get whatever value you need.
So to get the name which returns "USERNAME2":
username.get("name").getAsString();
Coming together with:
JsonObject obj = gson.fromJson(JSON_DOCUMENT, JsonObject.class);
JsonObject username = obj.get("USERNAME").getAsJsonObject();
username.get("name").getAsString();

Parse json with variable key

I just came up with challenging problem.
Below is json response where key is variable (a GUID)
How can I parse it? I've tried Google Gson, but that didn't work.
{
"87329751-7493-7329-uh83-739823748596": {
"type": "work",
"status": "online",
"icon": "landline",
"number": 102,
"display_number": "+999999999"
}
}

If you use Gson, in order to parse your response you can create a custom class representing your JSON data, and then you can use a Map.
Note that a Map<String, SomeObject> is exactly what your JSON represents, since you have an object, containing a pair of string and some object:
{ "someString": {...} }
So, first your class containing the JSON data (in pseudo-code):
class YourClass
String type
String status
String icon
int number
String display_number
Then parse your JSON response using a Map, like this:
Gson gson = new Gson();
Type type = new TypeToken<Map<String, YourClass>>() {}.getType();
Map<String, YourClass> map = gson.fromJson(jsonString, type);
Now you can access all the values using your Map, for example:
String GUID = map.keySet().get(0);
String type = map.get(GUID).getType();
Note: if you only want to get the GUID value, you don't need to create a class YourClass, and you can use the same parsing code, but using a generic Object in the Map, i.e., Map<String, Object>.

How to convert Json string with key-value pair into string with only value

I actually converted my pojo data into json string this way,
Gson gson = new GsonBuilder().disableHtmlEscaping().create();
String json=gson.toJson(user);
I got the json string but that is not the format i actually need, i got
json = {"userID":300,"userName":"asd","password":"s","enabled":1}
So, I want to convert Json string with key-value pair as below ,
{"userID":300,"userName":"asd","password":"s","enabled":1}
into Json string with only value (without key) as below
[300,"asd","s",1]

So I continue after your string json.
// lets deserialize your json string and get a hashmap
Type collectionType = new TypeToken<HashMap<String, Object>>(){}.getType();
HashMap<String, Object> hm = gson.fromJson(json, collectionType);
String finalJson = gson.toJson(hm.values());
// aand taa-daa!!
System.out.println(finalJson);
now finalJson is [300,"asd","s",1]
Edit: libraries are as following:
import java.lang.reflect.Type;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.reflect.TypeToken;

You could whack the properties of the user into a List<Object> and then JSON that.
This would mean GSON made an JSON array out of the List and you would get what you want.
As this doesn't seem to make much sense as a use case you would have to do a bit of hardcoding - I don't think GSON can do this for you:
final List<Object> props = new LinkedList<>();
props.add(user.getId());
props.add(user.getUserName());
//etc
final String json=gson.toJson(props);

Could I ask why do you want to do that? If you retrieve that Json without key-value how you will know, for example, that 300 is his id and not his money property?
You can't difference between your properties and I don't really recommend it.
Anyway, the only way I find to do that, is to "break" your string manually, replacing your properties with blank values, like json.replace("\"userID\"", ""); and you should do it for every property.

validate JSON string if the value of parameter is string or an array

this is JSON string 1
{"title":["1","2"], "amount":["1","2"]}
this is JSON string 2
{"title":"", "amount":""}
string 1 is created when I enter values in form and string 2 is created when I dont,
I want to know if the string is in format 1 that is title is an array ["1", "2"] or format 2 that is title is just a string "" on the server side in a servlet, before I parse it. is there any way of doing so?
this is my previous question,
How do I parse this JSON string using GSON in servlet
which is solved but as you can see there i have class Data which has instance variables of type ArrayList, so when I parse it with this line
Data data = gson.fromJson(param, Data.class);
it throws exception
com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was STRING at line 1 column 24
because as I have declared ArrayList, it expects array only in json to parse it without any exceptions....but when I dont enter values in my form it doesnt create json string as
{"title":[], "amount":[]}
rather it creates like this
{"title":'', "amount":''}
which has string as value, which causes parsing to throw exception

Had this problem as well and this is how I got around it
In your Data object have
public class Data {
// This is a generic object whose type is determined when used by GSON
private Object title;
// get the type of object and return as string
public String getTitleObjType() {
String objType = title.getClass().toString();
return objType;
}
// used if the object is an ArrayList, convert into an ArrayList<Object>
public ArrayList<String> getTitleArrayList() {
// Turn the Object into an arraylist
#SuppressWarnings("unchecked") // This is to counter the fact that the cast is not type safe
ArrayList<String> titleArrayList = (ArrayList<String>) title;
return titleArrayList;
}
// used if the object is not an array
public String getTitleStr() {
return title.toString();
}
}
When GSON builds the object it will create and each of these to be either a String or an ArrayList
Then when you want to use the objects, test to see what they are
ArrayList<String> titleValArrayList = new ArrayList<String>();
String titleValStr = "";
if(getTitleObjType.equals("class java.util.ArrayList")) {
titleValArrayList = getTitleArrayList();
//do whatever you like
}
else if(getTitleObjType.equals("class java.util.String")) {
titleValStr = getsTitleStr();
//do whatever you like
}

Check Google GSON it allows you to parse JSON server side.
It goes something like this:
String jsonString = request.getParameter("jsonParemeter");
Gson gson = new Gson();
Map fromJsonMap = gson.fromJson(jsonString, HashMap.class);
Object object = fromJsonMap.get("title");
if (object instanceof Collection) {
// then is it's your array
}
else {
// it's not
}
If, for example, I run the following example code:
String json1 = "{\"title\":[\"1\",\"2\"], \"amount\":[\"1\",\"2\"]}";
String json2 = "{\"title\":\"\", \"amount\":\"\"}";
Gson gson = new Gson();
HashMap map = gson.fromJson(json1, HashMap.class);
HashMap map2 = gson.fromJson(json2, HashMap.class);
System.out.println(map);
System.out.println(map2);
System.out.println(map.get("amount").getClass());
System.out.println(map2.get("amount").getClass());
I get as output:
{amount=[1, 2], title=[1, 2]}
{amount=, title=}
class java.util.ArrayList
class java.lang.String
If I understood you correctly I think it suits you 100%
UPDATE
Since you are trying to deserialize your JSON string directly to a Data object, if you want to keep doing that direct deserialization you have to use a custom deserialization mechanism