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6.2. Customizing Marshalling

Instead of using the default Marshaller, which may be slow with payloads that are unnecessarily large, objects may implement java.io.Externalizable so that a custom method of marshalling/unmarshalling classes is performed. With this approach the target class may be created in a variety of ways (direct instantiation, factory methods, reflection, etc.) and the developer has complete control over using the provided stream.
Implementing a Custom Externalizer

To configure a class for custom marshalling an implementation of org.infinispan.marshall.AdvancedExternalizer must be provided. Typically this is performed in a static inner class, as seen in the below externalizer for a Book class: 

import org.infinispan.marshall.AdvancedExternalizer;

public class Book {

   final String name;
   final String author;

   public Book(String name, String author) {
      this.name = name;
      this.author = author;
   }

   public static class BookExternalizer implements AdvancedExternalizer<Book> {
      @Override
      public void writeObject(ObjectOutput output, Book book)
            throws IOException {
         output.writeObject(book.name);
         output.writeObject(book.author);
      }

      @Override
      public Person readObject(ObjectInput input)
            throws IOException, ClassNotFoundException {
         return new Person((String) input.readObject(), (String) input.readObject());
      }

      @Override
      public Set<Class<? extends Book>> getTypeClasses() {
         return Util.<Class<? extends Book>>asSet(Book.class);
      }

      @Override
      public Integer getId() {
         return 2345;
      }
   }
}
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Once the writeObject() and readObject() methods have been implemented the Externalizer may be linked up with the classes they externalize; this is accomplished with the getTypeClasses() method seen in the above example.
In addition, a positive identifier must be defined as seen in the getId() method above. This value is used to identify the Externalizer at runtime. A list of values used by JBoss Data Grid, which should be avoided in custom Externalizer implementations, may be found at Section 6.3, “JBoss Data Grid Externalizer IDs”.
Registering Custom Marshallers

Custom Marshallers may be registered with JBoss Data Grid programmatically or declaratively, as seen in the following examples:

Example 6.1. Declaratively Register a Custom Marshaller

<cache-container>
  <serialization>
    <advanced-externalizer class="Book$BookExternalizer"/>
  </serialization>
</cache-container>
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Example 6.2. Programmatically Register a Custom Marshaller

GlobalConfigurationBuilder builder = ...
builder.serialization()
   .addAdvancedExternalizer(new Book.BookExternalizer());
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