APEX ENUM Serialize to and Deserialize from JSON

Question

I have APEX classes defined with enum properties that are to be serialized into JSON. Also, I am reading in JSON and deserializing them back to my defined classes.

To make the enum properties work with the JSON transitions, I have created another Integer property that gets the ordinal of the enum and sets the enum based on the enum's values list. See below:

Enum definitions:

public enum DataSourceType {
    NA,
    ArbitronSummary,
    ArbitronTally,
    NielsenSummary,
    NielsenTally,
    Scarborough,
    Strata,
    None
}
public enum FilterJoinType {
    AndJoin,
    OrJoin,
    NotJoin
}
public enum HourByHourInterval {
    NA0,
    NA1,
    Quarterly,
    NA3,
    Hourly
}

APEX Class definitions:

public class HourByHourRequest {
    public List<String> Books { get; set; }
    public DataSourceType eDataSource { get; set; }
    public Integer DataSource {
        get {
            if (eDataSource == null)
                return 0;
            return eDataSource.ordinal();
        }
        set {
            eDataSource = lib_ap.DataSourceType.values()[value];
        }
    }
    public FilterJoinType eFilterJoinType { get; set; }
    public Integer FilterJoinType {
        get {
            if (eFilterJoinType == null)
                return 0;
            return eFilterJoinType.ordinal();
        }
        set {
            eFilterJoinType = lib_ap.FilterJoinType.values()[value];
        }
    }
    public HourByHourInterval eInterval { get; set; }
    public Integer Interval {
        get {
            if (eInterval == null)
                return 0;
            return eInterval.ordinal();
        }
        set {
            eInterval = lib_ap.HourByHourInterval.values()[value];
        }
    }
}

APEX code using the class to serialize to JSON and deserialize from JSON:

HourByHourRequest request = new HourByHourRequest();

request.Books = new List<String>();
request.Books.add('BookName');

request.eDataSource = DataSourceType.ArbitronTally;
request.eFilterJoinType = FilterJoinType.AndJoin;
request.eInterval = HourByHourInterval.Hourly;

String jsonStr = JSON.serialize(request);
HourByHourRequest request2 = (HourByHourRequest)JSON.deserialize(request, HourByHourRequest.class);

The reason why I used an Integer property to go with each enum property is because upon serializing to JSON the enum value is lost. So having the corresponding Integer value retains the value in JSON, which can be deserialized back successfully... except in the code shown above. The above code will actually fail at the deserialize part due to a "Duplicate field" error for each of the enum/integer field pairs. Both the enum and integer fields are being included in the JSON string when serialized, even though only the integer field is retaining the value.

Sample JSON:

{"Interval":4,
"eInterval":{},
"FilterJoinType":0,
"eFilterJoinType":{},...

My question: Is there a way to ignore fields for serializing to JSON? That would resolve the "Duplicate field" error. Otherwise, how would I go about an appropriate way to handling enums when converting to/from JSON? Thanks!

Answer 1

Got an answer at https://salesforce.stackexchange.com/questions/18498/apex-enum-serialize-to-and-deserialize-from-json.

Basically, you can mark fields as transient to be ignored for serializing to JSON.