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How to receive customized JSON Object in Spring boot Api post Method

I am trying to receive a JSON object in #RequestBody which is not known to me i.e. the JSON Object could be of any length and data.
Let's say, JSON could be as shown below
{'seqNo': 10 }
{'country': 'US', 'state': 'CA'}
{'customer': 'Alex', product: 'UPS', date:'25-Mar-2018'}
And In Spring Boot Api, I have a method to receive that JSON Object.
#PostMapping(value = "/lookup")
public ResponseEntity<AppResponse> getLookup(#RequestBody LookupRequestObject lookupRequestObject) {
// THIS METHOD KNOWS WHICH FIELD TO USE
// FURTHER LOGIC WOULD BE HERE.
return ResponseEntity.ok(response);
}
I have read about Jackson Serialization but still finding solution for this.
Customize the Jackson ObjectMapper
Any help would be much appreciated.

You could just use a map for your input.
Then you can access filed in the map depending on what kind of fields it contains.
#PostMapping(value = "/lookup")
public ResponseEntity<AppResponse> getLookup(#RequestBody Map<String, Object> lookupRequestObject) {
// THIS METHOD KNOWS WHICH FIELD TO USE
// FURTHER LOGIC WOULD BE HERE.
return ResponseEntity.ok(response);
}

If JSON object structure is not known, you can always use Map<String, Object> type and convert it to POJO or directly work on Map. In case you need POJO you can use convertValue method:
#PostMapping(value = "/lookup")
public ResponseEntity<AppResponse> getLookup(#RequestBody Map<String, Object> payload) {
// read map
ObjectMapper objectMapper = new ObjectMapper();
if (payload.containsKey("seqNo")) {
Sequence seq = objectMapper.convertValue(payload, Sequence.class);
// other logic
} else if (payload.containsKey("country")) {
Country country = objectMapper.convertValue(payload, Country.class);
}
// the same for other types
// FURTHER LOGIC WOULD BE HERE.
return ResponseEntity.ok(response);
}
You can also try with deserialising to com.fasterxml.jackson.databind.JsonNode but it binds controller with Jackson which is not good from other side.

The answer by #Patrick Adler is absolutely correct. You can use Map as your parameter of the method. Two important additions: Map corresponds to JSON Object so when a JSON object is passed to your method Spring (using Jackson by default) will convert it to map, so no additional code needed. Also to be sure you can add to your annotation that you expect to receive JSON input:
So change the line
#PostMapping(value = "/lookup") to
#PostMapping(value = "/lookup", headers = "Accept=application/json") And finally the input that you posted is not a valid single JSON Object. It is 3 separate JSON Objects. So either you expect a JSON array containing JSON Objects or a Single JSON Object. If you expect a JSON Array then instead of Map<String, Object> parameter in your method use List<Map<String, Object>> so your solution should look either
#PostMapping(value = "/lookup", headers = "Accept=application/json")
public ResponseEntity<AppResponse> getLookup(#RequestBody Map<String, Object> lookupRequestObject) {
// THIS METHOD KNOWS WHICH FIELD TO USE
// FURTHER LOGIC WOULD BE HERE.
return ResponseEntity.ok(response);
}
or the same but with List<Map<String, Object>> param instead of just map

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-

How to parse the given string to map of string of map of string of object?

Hi my input string look like this
{
6138249={
value=[multi2, multi3, multi4],
key=TestMulticat
},
6161782={
value=Traps (Bamboo / Box),
key=Observation gear
}
}
I want to map this input string in Map<String,Map<String,Object>> in java.
As the input look more mysterious to me, i am not able to figure out the way to do the same.
I tried ObjectMapper class from jackson but still not able to map. The code i write look like this
Map<String,Map<String,Object>> data=objectMapper.readValue(singledoc, Map.class);
Can somebody suggest me either approach to do this or solution, both will be equally helpful.

Your input doesn't look like valid json, as it has unquoted string values.
Json would look like this:
{
6138249:{
value:["multi2", "multi3", "multi4"],
key:"TestMulticat"
},
6161782:{
value="Traps (Bamboo / Box)",
key="Observation gear"
}
}
For such input you can use jackson:
objectMapper.configure(JsonParser.Feature.ALLOW_UNQUOTED_FIELD_NAMES, true);
Map<String, Map<String, Object>> result = objectMapper
.readValue(test, new TypeReference<Map<String, Map<String, Object>>>() {});
ALLOW_UNQUOTED_FIELD_NAMES will help you to deal with unquoted field names, however there is no such option for unqouted values.
In your case as its not a json, you can either fix your serialization to produce valid jackson or write your own Deserializer for jackson handling this, because currently its not possible to read json with unquoted string values.

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();

Can't parse JSON array of arrays to LinkedHashMap in Jackson

I' m developing an Android REST client. We use JSON as data exchange format, so I use a Jackson parser. I get different Json responses from the server like simple arrays:
{"user_id":"332","user_role":"1"}
or something else. All these stuff I parse to LinkedHashMap<String, Object> and everything works perfectly but when I got this response from the server:
[ { "user_id":"352",
"user_role":"expert",
"name":"Test 12-18",
"description":"Test" },
{ "user_id":"263",
"user_role":"novice lab",
"name":"Tom's Desk",
"description":"Desk"}
]
I got null: {} after parsing.Here is my code where i use Jackson:
ObjectMapper mapParametersToJSON = new ObjectMapper();
String serverResponseBody = responseFromServer.getBody();
LinkedHashMap<String, Object> resultofOperation = new LinkedHashMap<String,
Object>();
TypeReference<LinkedHashMap<String,Object>> genericTypeReferenceInformation = new
TypeReference<LinkedHashMap<String,Object>>() {};
try {
resultofOperation = mapParametersToJSON.readValue(serverResponseBody,
genericTypeReferenceInformation);
So, why Jackson failed to parse this? How can I fix this?

Others have suggested the problem, but solutions are bit incomplete. If you need to deal with JSON Objects and Arrays, you can either bind to java.lang.Object, check the type:
Object stuff = objectMapper.readValue(json, Object.class);
and you will get either List or Map (specifically, ArrayList or LinkedHashMap, by default; these defaults can be changed).
Or you can do JSON trees with JsonNode:
JsonNode root = objectMapper.readTree(json);
if (root.isObject()) { // JSON Object
} else if (root.isArray()) { ...
}
latter is often more convenient.
One nice thing is that you can still create regular POJOs out of these, for example:
if (root.isObject()) {
MyObject ob = objectMapper.treeToValue(MyObject.class);
}
// or with Object, use objectMapper.convertValue(ob, MyObject.class)
so you can even have different handling for different types; go back and forth different representations.

The first JSON in your question is a map, or an object. The second is an array. You're not parsing an array, you're parsing a map.
You need to do something like this:
List<MyClass> myObjects = mapper.readValue(jsonInput, new TypeReference<List<MyClass>>(){});
Almost identical question with answer here.

In JSON the {"key": "value"} is Object and the ["this", "that"] is Array.
So, in case when you're receiving the array of objects you should use something like List<Map<Key, Value>>.

You are facing an error, because [] construction can't be translated into Map reference, only in List or array.
I would recommend do it something in this way:
ObjectMapper objectMapper = new ObjectMapper();
List<Map<String,String>> parsedResult = objectMapper.reader(CollectionType.construct(LinkedList.class, MapType.construct(LinkedHashMap.class, SimpleType.construct(String.class), SimpleType.construct(String.class)))).readValue(serverResponseBody);
//if you need the one result map
Map<String, String> resultMap = new LinkedHashMap<String, String>();
for (Map<String, String> map: parsedResult){
resultMap.putAll(map);
}