Parse List of JSON objects using GSON

Question

I have a JSON object like this:

{
  \"user1\": {
    \"timeSpent\": \"20.533333333333335h\",
    \"worklog\": [
      {
        \"date\": \"06/26/2013\",
            


        

Answer 1

I had some problem before a month. As far as I remember it was because, same as you, I forgot to make "new" to objects. I mean that it should look:

public class User {
    private String timeSpent;
    private List<WorkLog> worklogs = new List < WorkLog >();
}

Try this and I hope that it will help.

P.S. Also as Erik Pragt said you have array of Users, not just single one. So you will have to make 1 more class that contains a List < Users >.

Answer 2

Your JSON model does not match your object model.

You need an intermediate layer to fill the gap: a TypeAdapter.

Moreover there is no naming information for the user.

And finally there is a name mismatch: "worklog" in JSON, "worklogs" in Java.

Here is a fixed version:

Java model:

class User {
    private String timeSpent;
    @SerializedName("worklog")
    private List<WorkLog> worklogs = new LinkedList<WorkLog>();
    private String name;

    public List<WorkLog> getWorklogs() {
        return worklogs;
    }

    public void setWorklog(List<WorkLog> worklogs) {
        this.worklogs = worklogs;
    }

    public String getTimeSpent() {
        return timeSpent;
    }

    public void setTimeSpent(String timeSpent) {
        this.timeSpent = timeSpent;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

The plumbing to fill the gap:

class BookTypeAdapter implements JsonSerializer<Book>, JsonDeserializer<Book>
{
      Gson gson = new Gson();

      public JsonElement serialize(Book book, Type typeOfT, JsonSerializationContext context)
      {
          JsonObject json = new JsonObject();

          for (User user : book.getUser())
          {
              json.addProperty(user.getName(), gson.toJson(user));
          }

          return json;
      }

      public Book deserialize(JsonElement element, Type typeOfT, JsonDeserializationContext context) throws JsonParseException
      {
          JsonObject json = element.getAsJsonObject();

          Book book = new Book();

          for (Entry<String, JsonElement> entry : json.entrySet())
          {
              String name = entry.getKey();
              User user = gson.fromJson(entry.getValue(), User.class);
              user.setName(name);

              book.getUser().add(user); 
          }

          return book;
      }
}

And a roundtrip:

GsonBuilder builder = new GsonBuilder();
builder.registerTypeAdapter(Book.class, new BookTypeAdapter());

Gson gson = builder.create();

Book book = gson.fromJson("{" +
        " \"user1\": {" +
        "   \"timeSpent\": \"20.533333333333335h\"," +
        "   \"worklog\": [" +
        "     {" +
        "       \"date\": \"06/26/2013\"," +
        "       \"issues\": [" +
        "         {" +
        "           \"issueCode\": \"COC-2\"," +
        "           \"comment\": \"\ncccccc\"," +
        "           \"timeSpent\": \"20.533333333333335h\"" +
        "         }" +
        "       ]," +
        "       \"dayTotal\": \"20.533333333333335h\"" +
        "     }" +
        "   ]" +
        " }," +
        " \"admin\": {" +
        "   \"timeSpent\": \"601.1h\"," +
        "   \"worklog\": [" +
        "     {" +
        "       \"date\": \"06/25/2013\"," +
        "       \"issues\": [" +
        "         {" +
        "           \"issueCode\": \"COC-1\"," +
        "           \"comment\": \"\"," +
        "           \"timeSpent\": \"113.1h\"" +
        "         }" +
        "       ]," +
        "       \"dayTotal\": \"113.1h\"" +
        "     }," +
        "     {" +
        "       \"date\": \"06/26/2013\"," +
        "       \"issues\": [" +
        "         {" +
        "           \"issueCode\": \"COC-1\"," +
        "           \"comment\": \"\"," +
        "           \"timeSpent\": \"8h\"" +
        "         }," +
        "         {" +
        "           \"issueCode\": \"COC-2\"," +
        "           \"comment\": \"\"," +
        "           \"timeSpent\": \"480h\"" +
        "         }" +
        "       ]," +
        "       \"dayTotal\": \"488h\"" +
        "     }" +
        "   ]" +
        " }" +
        "}", Book.class);

String json = gson.toJson(book);

Have a look at my tutorial to get an idea of what is possible with Gson: Java/JSON mapping with Gson

Enjoy! :)