Joda DateTime deserialized from JSON as current timestamp instead of provided data

Question

I have a JSON with Joda DateTime field. It has some sample values. But whenever I convert it to Object it automatically takes the current DateTime instead of the DateTime present in the JSON.

PFB the sample JSON

[{
"pas": "CSP",
"policyNumber": "ZU131874",
"schemeName": "PepsiCo employee scheme20",
"policyStatus": "ACTIVE",
"productCode": "GPP",
"totalSavings": 100000,
"investmentReturn": 55000,
"effectiveDate": {
    "startDate": {
        "dayOfYear": 2,
        "year": 2014,
        "dayOfMonth": 2,
        "dayOfWeek": 4,
        "era": 1,
        "weekOfWeekyear": 1,
        "millisOfSecond": 0,
        "secondOfMinute": 0,
        "minuteOfDay": 0,
        "centuryOfEra": 20,
        "yearOfCentury": 14,
        "hourOfDay": 0,
        "monthOfYear": 1,
        "weekyear": 2014,
        "minuteOfHour": 0,
        "yearOfEra": 2014,
        "secondOfDay": 0,
        "millisOfDay": 0,
        "millis": 1388601000000
    },
    "endDate": null
}
}, {
"pas": "CSP",
"policyNumber": "ZU146271",
"schemeName": "PepsiCo employee scheme7",
"policyStatus": "ACTIVE",
"productCode": "GPP",
"totalSavings": 100000,
"investmentReturn": 55000,
"effectiveDate": {
    "startDate": {
        "dayOfYear": 156,
        "year": 2015,
        "dayOfMonth": 5,
        "dayOfWeek": 5,
        "era": 1,
        "weekOfWeekyear": 23,
        "millisOfSecond": 0,
        "secondOfMinute": 0,
        "minuteOfDay": 0,
        "centuryOfEra": 20,
        "yearOfCentury": 15,
        "hourOfDay": 0,
        "monthOfYear": 6,
        "weekyear": 2015,
        "minuteOfHour": 0,
        "yearOfEra": 2015,
        "secondOfDay": 0,
        "millisOfDay": 0,
        "millis": 1433442600000
    },
    "endDate": null
}
}]

I am using following code to convert list of JSON objects to a list Of Java objects.

policies = new ArrayList<Policy>();

JsonParser parser = new JsonParser();
JsonElement jsonElement = parser.parse(new FileReader("./src/test/resources/" + "sample-zurich-pensions.json"));
Type listType = new TypeToken<List<Policy>>(){}.getType();
List<Policy> policyList = new Gson().fromJson(jsonElement, listType);
policies.addAll(policyList);

In the jsonElement I am getting the exact value, but in the policyList the DateTime is set to the current date.

PFB the classes Policy.java

private String pas;
private String policyNumber;
private String schemeName;  
private String policyStatus;
private String productCode;
private BigDecimal totalSavings;
private BigDecimal investmentReturn;
private EffectiveDate effectiveDate;

EffectiveDate.java

private DateTime startDate;
private DateTime endDate;

Answer 1

During deserialization from JSON, Gson is creating a new DateTime() (which is equal to current system DateTime). The fields present in your JSON are based on getters in DateTime , but there are no setters for them present, so the object cannot be adjusted to the timestamp represented by the JSON. You are much better off using a standard date-time representation like ISO 8601 . Then, implement a JsonSerializer and JsonDeserializer for DateTime as suggested on the Gson site :

class DateTimeTypeConverter implements JsonSerializer<DateTime>, JsonDeserializer<DateTime> {

    @Override
    public JsonElement serialize(DateTime src, Type srcType, JsonSerializationContext context) {
        return new JsonPrimitive(src.toString());
    }

    @Override
    public DateTime deserialize(JsonElement json, Type type, JsonDeserializationContext context)
            throws JsonParseException {
        return new DateTime(json.getAsString());
    }
}

or use one of the solutions provided in this post (linked also by @user2762451). You can register the serializer/deserializer like this:

GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.registerTypeAdapter(DateTime.class, new DateTimeTypeConverter());
Gson gson = gsonBuilder.create();