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https://issues.apache.org/jira/browse/OPENNLP-776?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15428454#comment-15428454
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Tristan Nixon commented on OPENNLP-776:
---------------------------------------

Good point. I thought the only way to provide custom serialization was to use 
Externalizable, which does require a no-arg constructor, but now I see one can 
put the readObject and writeObject methods into a Serializable and get the same 
effect (leaving me wondering what the point of Externalizable is...).

One slight complication with this is that if we rely on Object's no-arg 
constructor, the implicit initialization of fields like artifactMap and 
artifactSerializers does not happen, so I need to do this explicitly in the 
readObject method, meaning they cannot be final anymore (nor can 
isLoadedFromSerialized). 

Otherwise, it seems to be working fine! See the attached patch.

> Model Objects should be Serializable
> ------------------------------------
>
>                 Key: OPENNLP-776
>                 URL: https://issues.apache.org/jira/browse/OPENNLP-776
>             Project: OpenNLP
>          Issue Type: Improvement
>    Affects Versions: tools-1.5.3
>            Reporter: Tristan Nixon
>            Assignee: Joern Kottmann
>            Priority: Minor
>              Labels: features, patch
>             Fix For: 1.6.1
>
>         Attachments: externalizable.patch, serialization_proxy.patch
>
>
> Marking model objects (ParserModel, SentenceModel, etc.) as Serializable can 
> enable a number of features offered by other Java frameworks (my own use case 
> is described below). You've already got a good mechanism for 
> (de-)serialization, but it cannot be leveraged by other frameworks without 
> implementing the Serializable interface. I'm attaching a patch to BaseModel 
> that implements the methods in the java.io.Externalizable interface as 
> wrappers to the existing (de-)serialization methods. This simple change can 
> open up a number of useful opportunities for integrating OpenNLP with other 
> frameworks.
> My use case is that I am incorporating OpenNLP into a Spark application. This 
> requires that components of the system be distributed between the driver and 
> worker nodes within the cluster. In order to do this, Spark uses Java 
> serialization API to transmit objects between nodes. This is far more 
> efficient than instantiating models on each node independently.



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