Custom java object serialization

[alolis]

Hello,

I am trying to serialize a custom java object and, of course, i am getting

Caused by: java.lang.IllegalArgumentException: No method in multimethod 'print-dup' for dispatch value

Is there a recommended way with nippy to serialize custom objects or do i need to defmethod print-dup MyObject to make this work?

Thank you for your time

[ptaoussanis]

Hi Alexander,

Nippy serializes in two ways:

1. Via a fast, binary serialization when available for the data type. Most standard Clojure types have a built-in implementation.
2. As a fallback, via the Clojure Reader.

(1) Isn't actually extensible atm for the following reasons:

• It's a relatively rare requirement.
• Since type thawing depends on a unique type id, there's potential for disagreement between extensions.
• The Reader already provides a very well thought-out extension mechanism.

So in your case, basically, you will want to look at extending the Reader. Nippy will then use the appropriate Reader extension via its fallback mechanism. Some resources: https://github.com/clojure/clojure/blob/master/src/clj/clojure/uuid.clj http://www.infoq.com/interviews/hickey-clojure-reader https://github.com/clojure/clojure/blob/master/changes.md#21-reader-literals

Note that the extensible Reader requires Clojure 1.4+.

Hope that helps! Cheers :-)

[alolis]

Thanks a lot for the info. I will see how I will handle this :)