7.2. Annotating Objects for Marshalling Using @SerializeWith

Objects can be marshalled by providing an Externalizer implementation for the type that needs to be marshalled or unmarshalled, then annotating the marshalled type class with @SerializeWith indicating the Externalizer class to use.

Example 7.1. Using the @SerializeWith Annotation

import org.infinispan.commons.marshall.Externalizer;
import org.infinispan.commons.marshall.SerializeWith;
 
@SerializeWith(Person.PersonExternalizer.class)
public class Person {
 
   final String name;
   final int age;
 
   public Person(String name, int age) {
      this.name = name;
      this.age = age;
   }
 
   public static class PersonExternalizer implements Externalizer<Person> {
      @Override
      public void writeObject(ObjectOutput output, Person person) 
            throws IOException {
         output.writeObject(person.name);
         output.writeInt(person.age);
      }
 
      @Override
      public Person readObject(ObjectInput input) 
            throws IOException, ClassNotFoundException {
         return new Person((String) input.readObject(), input.readInt());
      }
   }
}
In the provided example, the object has been defined as marshallable due to the @SerializeWith annotation. JBoss Marshalling will therefore marshall the object using the Externalizer class passed.
This method of defining externalizers is user friendly, however it has the following disadvantages:
  • The payload sizes generated using this method are not the most efficient. This is due to some constraints in the model, such as support for different versions of the same class, or the need to marshall the Externalizer class.
  • This model requires the marshalled class to be annotated with @SerializeWith, however an Externalizer may need to be provided for a class for which source code is not available, or for any other constraints, it cannot be modified.
  • Annotations used in this model may be limiting for framework developers or service providers that attempt to abstract lower level details, such as the marshalling layer, away from the user.
Advanced Externalizers are available for users affected by these disadvantages.

Note

To make Externalizer implementations easier to code and more typesafe, define type <t> as the type of object that is being marshalled or unmarshalled.