Need field-specific information in custom JsonSerializer

In my use case, I need to truncate some long String to fit the need of mobile 
client while still keeping the full String for web.

So I built two separate Gson objects for web and mobile, and specify some 
annotation on String field which needs to be truncated:

class Foo {
  @MobileJsonTruncate(70)
  String message;
}

But in the custom JsonSerializer, I have little information about the field 
being serialized, thus I can't get the annotation to determine whether to 
truncate and how long to keep.

Ideally, if we have the FieldAttributes information as a parameter of 
serialize() method or stored within JsonSerializationContext, that will be a 
easy job.

But now, I have to write an ugly work around like this:

class MobileJsonSerializer implements ExclusionStrategy, JsonSerializer<String> 
{

    @Override
    public boolean shouldSkipField(final FieldAttributes aField) {
        iField = aField;
        return aField.getAnnotation(WebExclusive.class) != null;
    }

    @Override public JsonElement serialize(final String aSrc, final Type aTypeOfSrc, final JsonSerializationContext aContext) {
        final MobileTruncate annotation = iField.getAnnotation(MobileTruncate.class);
        if (annotation == null)
            return aContext.serialize(aSrc);
        final JsonPrimitive result = new JsonPrimitive(aSrc.substring(0, Math.min(aSrc.length(), annotation.value())));
        iField = null;
        return result;
    }

    @Override public boolean shouldSkipClass(final Class<?> clazz) { return false; }

    private FieldAttributes iField;
}

Original issue reported on code.google.com by oasisfeng on 1 Apr 2011 at 1:34

[narramadan]

Need this feature.

I have a specific use case to serialize OffsetDateTime to String, but for specific fields I need to consider only the date part.

[mishrabhilash]

plus one for the feature