Question

I have a .net Webservice which should communicate with a Java app via json.

Now I have a method on the server side that looks like this:

    [WebMethod]
    [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
    public DateTime GetDate(DateTime input)
    {
        return input;
    }

from a C# app I can send a receive DateTime value. It’s a convention that Date values are serialized as:

\/Date(1279176056000)\/

where the number is defined as seconds since epoch.
So if I want to call that service my json request string must look like this:

{"input":"\/Date(1279176056000)\/"}

Howevery, I don’t know how to achive that with the json.org.* classes on the Java side.
The problem: If I use this code:

JSONObject json = new JSONObject();
json.put("input", "\\/Date(1279176056000)\\/");

the JSONObject is smart enough to escape the string itself before sending it through the wire, so I get:

{"input":"\\/Date(1279176056000)\\/"}

which results in an Exception during server side deserialisation:

System.FormatException: \/Date(1279183256000)\/ is not a valid value for DateTime
bei System.ComponentModel.DateTimeConverter.ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, Object value)
bei System.Web.Script.Serialization.ObjectConverter.ConvertObjectToTypeInternal(Object o, Type type, JavaScriptSerializer serializer, Boolean throwOnError, Object& convertedObject)
bei System.Web.Script.Serialization.ObjectConverter.ConvertObjectToTypeMain(Object o, Type type, JavaScriptSerializer serializer, Boolean throwOnError, Object& convertedObject)
bei System.Web.Script.Serialization.ObjectConverter.ConvertObjectToType(Object o, Type type, JavaScriptSerializer serializer)
bei System.Web.Script.Services.WebServiceMethodData.StrongTypeParameters(IDictionary`2 rawParams)
bei System.Web.Script.Services.WebServiceMethodData.CallMethodFromRawParams(Object target, IDictionary`2 parameters)
bei System.Web.Script.Services.RestHandler.InvokeMethod(HttpContext context, WebServiceMethodData methodData, IDictionary`2 rawParams)
bei System.Web.Script.Services.RestHandler.ExecuteWebServiceCall(HttpContext context, WebServiceMethodData methodData)

Long story short: How can I pass a backslash as a parameter to JSONObject without having it escaped?

Well, you might think I just just build the JSON string myself but I really want to send and receive more complex objects/arrays containing Date properties and I don’t want to handle the whole JSON generation myself.

Answer 1

Here is my own solution:

import java.util.Date;

public class DateConverter {

    private static long TicksToMillisOffset = 621355968000000000L;
    private static long TicksPerMillisecond = 10000L;

    public static Long toTicks(Date date)
    {
        if (date == null) return null;

        int offset = date.getTimezoneOffset() * 60;
        long ms = date.getTime();

        return (ms + offset) * TicksPerMillisecond + TicksToMillisOffset;   
    }

    public static Date fromTicks(Long ticks)
    {
        return ticks == null 
            ? null
            : new Date((ticks - TicksToMillisOffset) / TicksPerMillisecond);
    }

    public static String toJSONString(Date date) {
        return date != null ? date.toGMTString() : null;
    }

    public static Date fromJSONString(String string) {

        // expected: "/Date(secondssinceepoch)/"
        if (string.matches("^/Date\\(\\d+\\)/$")) {
            String value = string.replaceAll("^/Date\\((\\d+)\\)/$", "$1");
            return new Date(Long.valueOf(value));
        }
        else {
            return new Date(Date.parse(string));
        }

    }

}

usage:

// deserialisation:
JSONObject json = GetJSONObjectFromNetWebService();

Poco item = new Poco();
item.id = json.getInt("Id");
item.name = json.GetString("Name");
item.dateValue = DateConverter.fromJSONString(json.getString("DateValue"));

// serialisation
JSONObject json = new JSONObject();

Poco item = GetPocoFromSomeWhereElse();
json.put("Id", item.id);
json.put("Name", item.name);
json.put("DateValue", DateConverter.toJSONString(item.dateValue));