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Implementing HazelcastInstanceAware

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

Let’s implement it for the Employee class mentioned in the Custom Serialization section.

public class PersonAwr implements Serializable, HazelcastInstanceAware {

    private static final long serialVersionUID = 1L;

    private String name;

    private transient HazelcastInstance hazelcastInstance;

    PersonAwr(String name) {
        this.name = name;
    }

    public HazelcastInstance getHazelcastInstance() {
        return hazelcastInstance;
    }

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

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

After deserialization, the object is checked to see if it implements HazelcastInstanceAware and the method setHazelcastInstance is called. Notice the hazelcastInstance is transient. This 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 example, 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 set the HazelcastInstance field while using setHazelcastInstance method and you not execute operations on the HazelcastInstance. The reason is that when HazelcastInstance is injected for a HazelcastInstanceAware implementation, it may not be up and running at the injection time.