Calculated Fields

It is possible to create a ValueField for which the value is not stored in the database, but rather derived based on other values.

First, you will need to define a ValueField with fieldType set to CALCULATED_FIELD:

<field name="totalWeight">
  <fieldType>CALCULATED_FIELD</fieldType>
  <valueField>
    <valueFieldType component="" name="Long"/>
  </valueField>
</field>

After expanding this, the cruds class will contain a method stub to implement the calculation.

StarshipCruds

@Override
public CrudsResult<Long> performCalculateTotalWeight(ParameterContext<StarshipData> dataParameter) {
  StarshipData starshipData = dataParameter.getValue();
  Long result = null;

  // anchor:custom-calculation-totalWeight:start
  result = starshipData.getComponents().stream()
      .mapToLong(StarshipComponentData::getWeight)
      .sum();
  // anchor:custom-calculation-totalWeight:end

  return CrudsResult.success(result);
}

You can then add this Field to a Projection, or as an info Field.