Can anyone tell me why this error?

**Server Log:** 

```
 StandardWrapperValve[ws_site.ApplicationConfig]: Servlet.service() for servlet ws_site.ApplicationConfig threw exception
java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column 5
at com.google.gson.stream.JsonReader.expect(JsonReader.java:339)
    at com.google.gson.stream.JsonReader.beginObject(JsonReader.java:322)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:165)
    at com.google.gson.Gson.fromJson(Gson.java:791)

```

Javascript function, responsible for capturing the data of the filled form and sending to the server:

```
function save()
{

    var str_name = $("#name").val();
    var str_email = $("#email").val();

    var str_country = $("#country").val();
    var str_state = $("#state").val();
    var str_city = $("#city").val();
    var str_zipcode = $("#zipcode").val();
    var str_neighborhood = $("#neighborhood").val();
    var str_street = $("#street").val();
    var str_number = $("#number").val();

    var objdata = '{"email_user":"' + str_email + '","name_user":"' + str_name}';
var objlocation = '{"country":"' + str_country + '","state":"' + str_state + '","city":"' + str_city + '","neighborhood":"' + str_neighborhood + '","street":"' + str_street + '","number":"' + str_number + '","zipcode":"' + str_zipcode + '"}';

    var obj = '{"user":['+objdata+'],"endereco":['+objlocation+']}';

    $.ajax({
        headers: {'content-type': 'application/json'},
        dataType: 'json',
        method: "POST",
        url: "http://localhost:8080/SystemExample/webservice/Save/data",
        data: obj
     }).done(function (data)
     {
        alert(data);
     });
}

```

Restful Java method:

```
@POST
@Path("data")
@Produces(MediaType.TEXT_PLAIN)
@Consumes({MediaType.APPLICATION_JSON})
public String registerUser(Gson json)  
{
    User u = json.fromJson("user", User.class);
    Address a = json.fromJson("endereco", Address.class);
    u.setAddress(a);
    userDAO.save(u);
    return "Saved successfully!";
}

```

Save userDAO method:

```
    public void save(User u) {
    EntityManager em = JPAUtil.getEntityManager();
    EntityTransaction tx = em.getTransaction();

    try {
        tx.begin();
        if (u.getId_User() == null) {

            em.persist(u);
        } else {
            em.merge(u);
        }
        tx.commit();
    } catch (Exception ex) {
        ex.printStackTrace();
        if (tx != null && tx.isActive()) {
            tx.rollback();
        }
    } finally {
        em.close();
    }
}

```

Using Gson to convert json into an object