How to use org.apache.cassandra.cql3.functions

private ByteBuffer executeAsync(ProtocolVersion protocolVersion, List<ByteBuffer> parameters)
{
  ThreadIdAndCpuTime threadIdAndCpuTime = new ThreadIdAndCpuTime();
  return async(threadIdAndCpuTime, () -> {
    threadIdAndCpuTime.setup();
    return executeUserDefined(protocolVersion, parameters);
  });
}

private GenericFunctionRegistry() 
{
  this.registry = new HashMap<String, Class<? extends IGenericFunction>>() 
  {{
    put(ToJsonFct.NAME.name(), ToJsonFct.class); 
  }};
}

/**
 * Like {@link #executeAsync(int, List)} but the first parameter is already in non-serialized form.
 * Remaining parameters (2nd paramters and all others) are in {@code parameters}.
 * This is used to prevent superfluous (de)serialization of the state of aggregates.
 * Means: scalar functions of aggregates are called using this variant.
 */
private Object executeAggregateAsync(ProtocolVersion protocolVersion, Object firstParam, List<ByteBuffer> parameters)
{
  ThreadIdAndCpuTime threadIdAndCpuTime = new ThreadIdAndCpuTime();
  return async(threadIdAndCpuTime, () -> {
    threadIdAndCpuTime.setup();
    return executeAggregateUserDefined(protocolVersion, firstParam, parameters);
  });
}

private static Functions functions()
{
  return Functions.builder()
          .add(UuidFcts.all())
          .add(TimeFcts.all())
          .add(BytesConversionFcts.all())
          .add(AggregateFcts.all())
          .add(CastFcts.all())
          .build();
}

  public Aggregate newAggregate()
  {
    return new LongSumAggregate();
  }
};

/**
 * Used by UDF implementations (both Java code generated by {@link JavaBasedUDFunction}
 * and script executor {@link ScriptBasedUDFunction}) to convert the Java
 * object representation for the return value to the C* serialized representation.
 *
 * @param protocolVersion the native protocol version used for serialization
 */
protected ByteBuffer decompose(ProtocolVersion protocolVersion, Object value)
{
  return decompose(returnCodec, protocolVersion, value);
}

  AggregateFunctionSelector(Function fun, List<Selector> argSelectors) throws InvalidRequestException
  {
    super((AggregateFunction) fun, argSelectors);

    this.aggregate = this.fun.newAggregate();
  }
}

public static <I, O> CassandraFunctionWrapper<I, O> create(AbstractType<I> inputType,
                              AbstractType<O> outputType,
                              NativeScalarFunction delegate)
{
  return new CassandraFunctionWrapper<I, O>(inputType, outputType, delegate);
}

public static <I> CastAsTextFunction<I> create(AbstractType<I> inputType,
                        AbstractType<String> outputType)
{
  return new CastAsTextFunction<I>(inputType, outputType);
}

public static <I, O> JavaFunctionWrapper<I, O> create(AbstractType<I> inputType,
                           AbstractType<O> outputType,
                           java.util.function.Function<I, O> converter)
{
  return new JavaFunctionWrapper<I, O>(inputType, outputType, converter);
}

public UDFByteCodeVerifier()
{
  addDisallowedMethodCall(OBJECT_NAME, "clone");
  addDisallowedMethodCall(OBJECT_NAME, "finalize");
  addDisallowedMethodCall(OBJECT_NAME, "notify");
  addDisallowedMethodCall(OBJECT_NAME, "notifyAll");
  addDisallowedMethodCall(OBJECT_NAME, "wait");
}

private static Functions functions()
{
  return Functions.builder()
          .add(UuidFcts.all())
          .add(TimeFcts.all())
          .add(BytesConversionFcts.all())
          .add(AggregateFcts.all())
          .add(CastFcts.all())
          .build();
}

private ByteBuffer executeAsync(ProtocolVersion protocolVersion, List<ByteBuffer> parameters)
{
  ThreadIdAndCpuTime threadIdAndCpuTime = new ThreadIdAndCpuTime();
  return async(threadIdAndCpuTime, () -> {
    threadIdAndCpuTime.setup();
    return executeUserDefined(protocolVersion, parameters);
  });
}

/**
 * Like {@link #executeAsync(int, List)} but the first parameter is already in non-serialized form.
 * Remaining parameters (2nd paramters and all others) are in {@code parameters}.
 * This is used to prevent superfluous (de)serialization of the state of aggregates.
 * Means: scalar functions of aggregates are called using this variant.
 */
private Object executeAggregateAsync(ProtocolVersion protocolVersion, Object firstParam, List<ByteBuffer> parameters)
{
  ThreadIdAndCpuTime threadIdAndCpuTime = new ThreadIdAndCpuTime();
  return async(threadIdAndCpuTime, () -> {
    threadIdAndCpuTime.setup();
    return executeAggregateUserDefined(protocolVersion, firstParam, parameters);
  });
}

  public Aggregate newAggregate()
  {
    return new LongSumAggregate();
  }
};

/**
 * Used by UDF implementations (both Java code generated by {@link JavaBasedUDFunction}
 * and script executor {@link ScriptBasedUDFunction}) to convert the Java
 * object representation for the return value to the C* serialized representation.
 *
 * @param protocolVersion the native protocol version used for serialization
 */
protected ByteBuffer decompose(ProtocolVersion protocolVersion, Object value)
{
  return decompose(returnCodec, protocolVersion, value);
}

  AggregateFunctionSelector(Function fun, List<Selector> argSelectors) throws InvalidRequestException
  {
    super((AggregateFunction) fun, argSelectors);

    this.aggregate = this.fun.newAggregate();
  }
}

public static <I, O> CassandraFunctionWrapper<I, O> create(AbstractType<I> inputType,
                              AbstractType<O> outputType,
                              NativeScalarFunction delegate)
{
  return new CassandraFunctionWrapper<I, O>(inputType, outputType, delegate);
}

private static Functions functions()
{
  return Functions.builder()
          .add(UuidFcts.all())
          .add(TimeFcts.all())
          .add(BytesConversionFcts.all())
          .add(AggregateFcts.all())
          .add(CastFcts.all())
          .build();
}

private ByteBuffer executeAsync(ProtocolVersion protocolVersion, List<ByteBuffer> parameters)
{
  ThreadIdAndCpuTime threadIdAndCpuTime = new ThreadIdAndCpuTime();
  return async(threadIdAndCpuTime, () -> {
    threadIdAndCpuTime.setup();
    return executeUserDefined(protocolVersion, parameters);
  });
}