Documentation Version: 3.3 - Publication Date : Sep 07, 2014

HazelcastInstanceAware Interface

You can implement HazelcastInstanceAware interface to access distributed objects for some cases where an object is deserialized and needs access to HazelcastInstance.

Let's implement it for the Employee class mentioned in previous sections.

public class Employee
    implements Serializable, HazelcastInstanceAware { 

  private static final long serialVersionUID = 1L;
  private String surname;
  private transient HazelcastInstance hazelcastInstance;

  public Person( String surname ) { 
    this.surname = surname;
  }

  @Override
  public void setHazelcastInstance( HazelcastInstance hazelcastInstance ) {
    this.hazelcastInstance = hazelcastInstance;
    System.out.println( "HazelcastInstance set" ); 
  }

  @Override
  public String toString() {
    return String.format( "Person(surname=%s)", surname ); 
  }
}

After deserialization, object is checked whether it implements HazelcastInstanceAware and the method setHazelcastInstance is called. Notice the hazelcastInstance being transient. It is because this field should not be serialized.

It may be a good practice to inject a HazelcastInstance into a domain object (e.g. Employee in the above sample) when used together with Runnable/Callable implementations. These runnables/callables are executed by IExecutorService which sends them to another machine. And after a task is deserialized, run/call method implementations need to access HazelcastInstance.

We recommend you only to set the HazelcastInstance field while using setHazelcastInstance method and not to execute operations on the HazelcastInstance. Because, when HazelcastInstance is injected for a HazelcastInstanceAware implementation, it may not be up and running at the injection time.