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Serialization Interface Types

For complex objects, use the following interfaces for serialization and deserialization:

When Hazelcast serializes an object:

  1. It first checks whether the object is null.

  2. If the above check fails, then Hazelcast checks if it is an instance of com.hazelcast.nio.serialization.DataSerializable or com.hazelcast.nio.serialization.IdentifiedDataSerializable.

  3. If the above check fails, then Hazelcast checks if it is an instance of com.hazelcast.nio.serialization.Portable.

  4. If the above check fails, then Hazelcast checks if it is an instance of one of the default types (see the Serialization chapter introduction for default types).

  5. If the above check fails, then Hazelcast looks for a user-specified Custom Serializer, i.e. an implementation of ByteArraySerializer or StreamSerializer. Custom serializer is searched using the input Object’s Class and its parent class up to Object. If parent class search fails, all interfaces implemented by the class are also checked (excluding java.io.Serializable and java.io.Externalizable).

  6. If the above check fails, then Hazelcast checks if it is an instance of java.io.Serializable or java.io.Externalizable and a Global Serializer is not registered with Java Serialization Override feature.

  7. If the above check fails, Hazelcast uses the registered Global Serializer if one exists.

If all of the above checks fail, then serialization fails. When a class implements multiple interfaces, the above steps are important to determine the serialization mechanism that Hazelcast uses. When a class definition is required for any of these serializations, you need to have all the classes needed by the application on your classpath because Hazelcast does not download them automatically, unless you are using user code deployment.