Parsing Dates Gson: NumberFormatException

Question

I'm fairly new to java and Gson and I've been trying to parse some date from the nobelprize.org api. I've been able to parse through some of the info but when I include dates I seem to always hit errors. How would i go about fixing this error?

I've tried .setDateFormat("yyyy-MM-dd") but I still get the same error.

Gson mainparser = new GsonBuilder()
.setDateFormat("yyyy-MM-dd")
.create();

mainparser.fromJson(line, ParsedJson.class);

public class ParsedJson {

    List<Laureates> laureates;

    public List<Laureates> getLaureates() {
        return laureates;
    }

    public void setLaureates(List<Laureates> laureates) {
        this.laureates = laureates;
    }


}

public class Laureates {
    int id;
    String firstname;
    String surname;
    Date born;
    Date died;
    String bornCountry;
    String bornCountryCode;
    String bornCity;
    String diedCountry;
    String diedCountryCode;
    String diedCity;
    String gender;
    List<Prizes> prizes;
...Getters/Setters

}

This is the error I get:

java.lang.reflect.InvocationTargetException

Caused by: com.google.gson.JsonSyntaxException: java.lang.NumberFormatException: For input string: "1845-03-27"

Caused by: java.lang.NumberFormatException: For input string: "1845-03-27"

*Edit: Example Json

    "laureates": [
        {
            "id": "1",
            "firstname": "Wilhelm Conrad",
            "surname": "Röntgen",
            "born": "1845-03-27",
            "died": "1923-02-10",
            "bornCountry": "Prussia (now Germany)",
            "bornCountryCode": "DE",
            "bornCity": "Lennep (now Remscheid)",
            "diedCountry": "Germany",
            "diedCountryCode": "DE",
            "diedCity": "Munich",
            "gender": "male",
            "prizes": [
                {
                    "year": "1901",
                    "category": "physics",
                    "share": "1",
                    "motivation": "\"in recognition of the extraordinary services he has rendered by the discovery of the remarkable rays subsequently named after him\"",
                    "affiliations": [
                        {
                            "name": "Munich University",
                            "city": "Munich",
                            "country": "Germany"
                        }
                    ]
                }
            ]
        },
]

https://stackoverflow.com/questions/6873020/gson-date-format check this — Rahul, Apr 10 '19 at 07:03
I recommend you don’t use `Date`. That class is poorly designed and long outdated. Instead use `LocalDate` from [java.time, the modern Java date and time API](https://docs.oracle.com/javase/tutorial/datetime/). — Ole V.V., Apr 10 '19 at 07:09
You're sure `"id": "1"` works? It's defined as an `int` in your code. — MC Emperor, Apr 10 '19 at 07:53

score 1 · Accepted Answer · answered Apr 10 '19 at 07:07

1

You can try to use JsonDeserializer for Date attributes.

public class DateDeserializer implements JsonDeserializer<Date> {

   public DateDeserializer() {
   }

    @Override
    public Date deserialize(JsonElement element, Type arg1, JsonDeserializationContext arg2) throws JsonParseException {
        String dateStr = element.getAsString();
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd", Locale.getDefault());
        try {
            return format.parse(dateStr);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        return null;
    }
}

in your model class add JsonAdapter for attributes

public class Laureates {
    int id;
    String firstname;
    String surname;
    @JsonAdapter(DateDeserializer.class)
    Date born;
    @JsonAdapter(DateDeserializer.class)
    Date died;
    String bornCountry;
    String bornCountryCode;
    String bornCity;
    String diedCountry;
    String diedCountryCode;
    String diedCity;
    String gender;
    List<Prizes> prizes;
...Getters/Setters

}

answered Apr 10 '19 at 07:07

Ergin Ersoy

890
8
28

Dumb question but how do I implement the JsonDeserializer class from your answer. As I seem to either get this: DateDeserializer is not abstract and does not override abstract method, And also this from the @Override: Method does not override or implement a method from a supertype – YamYam Apr 10 '19 at 07:41
I am not sure if i understand your question but. I think you thought `JsonDeserializer` is a custom class but it is `gson`'s class. – Ergin Ersoy Apr 10 '19 at 07:44
Oh sorry I meant to say how would I include DateDeserializer class, as currently it does not seem to override the method from JsonDeserializer and is giving me the not abstract/does not override errors from above – YamYam Apr 10 '19 at 07:50
`JsonDeserializer` is not an abstract class. It is an interface. You shouldn't get any errors. I am not sure why you are getting that error. You just needed to create a java file and copy paste the `DateDeserializer` class above. – Ergin Ersoy Apr 10 '19 at 07:59

Parsing Dates Gson: NumberFormatException

1 Answers1