Issue with parsing the content from JSON file with Jackson & message- JsonMappingException -Cannot deserialize as out of START_ARRAY token

Given the following .json file:

[    {        "name" : "New York",        "number" : "732921",        "center" : [                "latitude" : 38.895111,                 "longitude" : -77.036667            ]
    },
    {
        "name" : "San Francisco",
        "number" : "298732",
        "center" : [
                "latitude" : 37.783333, 
                "longitude" : -122.416667
            ]
    }
]

I prepared two classes to represent the contained data:

public class Location {
    public String name;
    public int number;
    public GeoPoint center;
}

...

public class GeoPoint {
    public double latitude;
    public double longitude;
}

In order to parse the content from the .json file I use Jackson 2.2.x and prepared the following method:

public static List<Location> getLocations(InputStream inputStream) {
    ObjectMapper objectMapper = new ObjectMapper();
    try {
        TypeFactory typeFactory = objectMapper.getTypeFactory();
        CollectionType collectionType = typeFactory.constructCollectionType(
                                            List.class, Location.class);
        return objectMapper.readValue(inputStream, collectionType);
    } catch (IOException e) {
        e.printStackTrace();
    }
    return null;
}

As long as I leave out the center property all content can be parsed. However, when I try to parse the geo-coordinates I end up with the following error message:

> com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of
> com.example.GeoPoint out of START_ARRAY token at [Source: android.content.res.AssetManager$AssetInputStream@416a5850; line: 5, column: 25]
> (through reference chain: com.example.Location["center"])

JsonMappingException: out of START_ARRAY token exception is thrown by Jackson object mapper as it's expecting an Object {} whereas it found an Array [{}] in response.

This can be solved by replacing Object with Object[] in the argument for geForObject("url",Object[].class). References:

1. Ref.1
2. Ref.2
3. Ref.3

Your JSON string is malformed: the type of center is an array of invalid objects. Replace [ and ] with { and } in the JSON string around longitude and latitude so they will be objects:

[    {        "name" : "New York",        "number" : "732921",        "center" : {                "latitude" : 38.895111,                 "longitude" : -77.036667            }    },    {        "name" : "San Francisco",        "number" : "298732",        "center" : {                "latitude" : 37.783333,                 "longitude" : -122.416667            }    }]

I sorted this problem as verifying the json from JSONLint.com and then, correcting it. And this is code for the same.

String jsonStr = "[{\r\n" + "\"name\":\"New York\",\r\n" + "\"number\": \"732921\",\r\n"+ "\"center\": {\r\n" + "\"latitude\": 38.895111,\r\n"	+ "	\"longitude\": -77.036667\r\n" + "}\r\n" + "},\r\n" + "	{\r\n"+ "\"name\": \"San Francisco\",\r\n" +\"number\":\"298732\",\r\n"+ "\"center\": {\r\n" + "	\"latitude\": 37.783333,\r\n"+ "\"longitude\": -122.416667\r\n" + "}\r\n" + "}\r\n" + "]";

ObjectMapper mapper = new ObjectMapper();
MyPojo[] jsonObj = mapper.readValue(jsonStr, MyPojo[].class);

for (MyPojo itr : jsonObj) {
	System.out.println("Val of name is: " + itr.getName());
	System.out.println("Val of number is: " + itr.getNumber());
	System.out.println("Val of latitude is: " + 
        itr.getCenter().getLatitude());
	System.out.println("Val of longitude is: " + 
        itr.getCenter().getLongitude() + "\n");
}

Note: MyPojo[].class is the class having getter and setter of json properties.

Result:

Val of name is: New York
Val of number is: 732921
Val of latitude is: 38.895111
Val of longitude is: -77.036667
Val of name is: San Francisco
Val of number is: 298732
Val of latitude is: 37.783333
Val of longitude is: -122.416667

As said, JsonMappingException: out of START_ARRAY token exception is thrown by Jackson object mapper as it's expecting an Object {} whereas it found an Array [{}] in response.

A simpler solution could be replacing the method getLocations with:

public static List<Location> getLocations(InputStream inputStream) {
    ObjectMapper objectMapper = new ObjectMapper();
    try {
        TypeReference<List<Location>> typeReference = new TypeReference<>() {};
        return objectMapper.readValue(inputStream, typeReference);
    } catch (IOException e) {
        e.printStackTrace();
    }
    return null;
}

On the other hand, if you don't have a pojo like Location, you could use:

TypeReference<List<Map<String, Object>>> typeReference = new TypeReference<>() {};
return objectMapper.readValue(inputStream, typeReference);

For instance:

data class

data class ToDo(
var id: Int, 
var text: String?, 
var completed: Boolean?) {}

Above deserialization error thrown when you use ToDo::class.java but not Array::class.java for json list

DOEST NOT WORK

    private val mapper = ObjectMapper().registerKotlinModule()
    .....
    val todo= mapper.readValue(response.body(), ToDo::class.java)

> com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot > deserialize value of type com.example.api.dto.ToDo from Array value > (token JsonToken.START_ARRAY) at [Source: > (String)"[{"id":14,"text":"TEST","completed":true},{"id":13,"text":"TEST","completed":true},{"id":19,"text":"TEST","completed":true"[truncated > 84 chars]; line: 1, column: 1]

WORK

private val mapper = ObjectMapper().registerKotlinModule()
.....
val todos = mapper.readValue(response.body(), Array<ToDo>::class.java)