Serialization Global Serializer

The global serializer is identical to custom serializers from the implementation perspective. The global serializer is registered as a fallback serializer to handle all other objects if a serializer cannot be located for them.

By default, the global serializer does not handle java.io.Serializable and java.io.Externalizable instances. However, you can configure it to be responsible for those instances.

A custom serializer should be registered for a specific class type. The global serializer will handle all class types if all the steps in searching for a serializer fail as described in Serialization Interface Types.

Use cases

• Third party serialization frameworks can be integrated using the global serializer.

• For your custom objects, you can implement a single serializer to handle all of them.

• You can replace the internal Java serialization by enabling the overrideJavaSerialization option of the global serializer configuration.

Any custom serializer can be used as the global serializer. Please refer to the Custom Serialization section for implementation details.

NOTE: To function properly, Hazelcast needs the Java serializable objects to be handled correctly. If the global serializer is configured to handle the Java serialization, the global serializer must properly serialize/deserialize the java.io.Serializable instances. Otherwise, it causes Hazelcast to malfunction.

Sample Global Serializer

A sample global serializer that integrates with a third party serializer is shown below.

public class GlobalStreamSerializer
    implements StreamSerializer<Object> {

  private SomeThirdPartySerializer someThirdPartySerializer;
  
  private init() {
    //someThirdPartySerializer  = ... 
  }
  
  @Override
  public int getTypeId () {
    return 123; 
  }

  @Override
  public void write( ObjectDataOutput out, Object object ) throws IOException { 
     byte[] bytes = someThirdPartySerializer.encode(object);
     out.writeByteArray(bytes);
  }

  @Override
  public Object read( ObjectDataInput in ) throws IOException { 
    byte[] bytes = in.readByteArray();
    return someThirdPartySerializer.decode(bytes);
  }

  @Override
  public void destroy () {
     someThirdPartySerializer.destroy();
  }
}

Now, we can register the global serializer in the configuration file hazelcast.xml, as shown below.

<serialization>
  <serializers>
    <global-serializer override-java-serialization="true">GlobalStreamSerializer</global-serializer>
  </serializers>
</serialization>