com.google.gson.JsonSyntaxException when trying to parse Date/Time in json

Question

I'm using RestTemplete to get json data from a rest api and I'm using Gson to parse data from json format to Object

Gson gson = new Gson();

restTemplate = new RestTemplate();
restTemplate.getMessageConverters().add(new GsonHttpMessageConverter());
restTemplate.getMessageConverters().add(new StringHttpMessageConverter());

List<Appel> resultList = null;

resultList = Arrays.asList(restTemplate.getForObject(urlService, Appel[].class));

but I get this problem with Date, what should I do ..

Could not read JSON: 1382828400000; nested exception is com.google.gson.JsonSyntaxException: 1382828400000

my Pojo that contains other pojos in it's body

public class Appel implements Serializable {

    private Integer numOrdre;
    private String reference;
    private String objet;
    private String organisme;
    private Double budget;
    private Double caution;
    private Date dateParution;
    private Date heureParution;
    private Date dateLimite;
    private Date heureLimite;
    private List<Support> supportList;
    private Ville villeid;
    private Categorie categorieid;

    public Appel() {
    }

    public Appel(Integer numOrdre, String reference, String objet, String organisme, Date dateParution, Date heureParution, Date dateLimite) {
        this.numOrdre = numOrdre;
        this.reference = reference;
        this.objet = objet;
        this.organisme = organisme;
        this.dateParution = dateParution;
        this.heureParution = heureParution;
        this.dateLimite = dateLimite;
    }

this is ths json returned by my API

[
   {
       "numOrdre": 918272,
       "reference": "some text",
       "objet": "some text",
       "organisme": "some text",
       "budget": 3000000,
       "caution": 3000000,
       "dateParution": 1382828400000,
       "heureParution": 59400000,
       "dateLimite": 1389657600000,
       "heureLimite": 34200000,
       "supportList":
       [
           {
               "id": 1,
               "nom": "some text",
               "dateSupport": 1384732800000,
               "pgCol": "013/01"
           },
           {
               "id": 2,
               "nom": "some text",
               "dateSupport": 1380236400000,
               "pgCol": "011/01"
           }
       ],
       "villeid":
       {
           "id": 2,
           "nom": "Ville",
           "paysid":
           {
               "id": 1,
               "nom": "Pays"
           }
       },
       "categorieid":
       {
           "id": 1,
           "description": "some text"
       }
   },
  .....
]

Answer 1

What I've done finally is going to my API project and create a CustomSerializer

public class CustomDateSerializer extends JsonSerializer<Date> {  

    @Override
    public void serialize(Date t, JsonGenerator jg, SerializerProvider sp) throws IOException, JsonProcessingException {
        SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
        String formattedDate = formatter.format(t);

        jg.writeString(formattedDate);
    }
}

that return the format yyyy-MM-dd and I annotated date fields with

@JsonSerialize(using = CustomDateSerializer.class)

in my Android application I created Gson object as

            Reader reader = new InputStreamReader(content);

            GsonBuilder gsonBuilder = new GsonBuilder();
            gsonBuilder.setDateFormat("yyyy-MM-dd");
            Gson gson = gsonBuilder.create();
            appels = Arrays.asList(gson.fromJson(reader, Appel[].class));
            content.close();

and it works for now .. thanks for your help I appreciate it

Answer 2

Custom Serializers are no longer necessary - simply use GsonBuilder, and specify the date format, as such:

Timestamp t = new Timestamp(System.currentTimeMillis());

String json = new GsonBuilder()
               .setDateFormat("yyyy-MM-dd hh:mm:ss.S")
               .create()
               .toJson(t);

System.out.println(json);

Answer 3

The 1382828400000 value is a long (time in milliseconds). You are telling GSON that the field is a Date, and it cannot automatically convert a long into a Date.

You have to specify your fields as long values

private long dateParution;
private long heureParution;
private long dateLimite;
private long heureLimite;

and after GSON casts the JSON string to the desired Appel class instance, construct another object with those fields as Dates and convert them while assigning the values to the new object.

Another alternative is to implement your own Custom Deserializer:

 public class CustomDateDeserializer extends DateDeserializer {
     @Override
     public Date deserialize(JsonParser jsonParser, DeserializationContext context) throws IOException, JsonProcessingException {
         // get the value from the JSON
         long timeInMilliseconds = Long.parseLong(jsonParser.getText());

         Calendar calendar = Calendar.getInstance();
         calendar.setTimeInMillis(timeInMilliseconds);
         return calendar.getTime();
     }
 }

You have to set this custom deserializer on your desired fields, on the setter methods, like:

@JsonDeserialize(using=CustomDateDeserializer.class)
public void setDateParution(Date dateParution) {
    this.dateParution = dateParution;
}