9.16. Feature-To-Feature Converter

The feature-to-feature converter can be used to transform SimpleFeatures from one SimpleFeatureType to another. Unlike other GeoMesa converters, the feature-to-feature converter must be invoked programmatically, as there is no native decoding of features from an input stream.

9.16.1. Configuration

The feature-to-feature converter expects a type of simple-feature. It also requires the input feature type to be defined with input-sft, which must reference the name of a feature type available on the classpath - see Defining SimpleFeatureTypes for details on making the feature type available.

The fields of the converter can reference the attributes of the input feature type by name, using $ notation. Any fields that have the same name as the input type will be automatically copied, unless they are explicitly redefined in the converter definition. The feature ID will also be copied, unless it is redefined with id-field.

9.16.2. Example Usage

Given an input feature type defined as:

geomesa.sfts.intype = {
  type-name = "intype"
  attributes = [
    { name = "number", type = "Integer" }
    { name = "color",  type = "String"  }
    { name = "weight", type = "Double"  }
    { name = "geom",   type = "Point"   }
  ]
}

And an output feature type defined as:

geomesa.sfts.outtype = {
  type-name = "outtype"
  attributes = [
    { name = "number",   type = "Integer" }
    { name = "color",    type = "String"  }
    { name = "weight",   type = "Double"  }
    { name = "numberx2", type = "Integer" }
    { name = "geom",     type = "Point"   }
  ]
}

The following example will copy the attributes of the input features, while adding a new attribute (numberx2) derived from one of the input fields:

geomesa.converters.myconverter = {
  type = "simple-feature"
  input-sft = "intype"
  fields = [
    // note: number, color, weight, and geom will be auto-copied since they exist in both input and output types
    { name = "numberx2", transform = "add($number, $number)::int" }
  ]
}

ScalaJava

import org.geotools.api.feature.simple.SimpleFeature
import org.locationtech.geomesa.convert.ConverterConfigLoader
import org.locationtech.geomesa.convert2.simplefeature.FeatureToFeatureConverter
import org.locationtech.geomesa.utils.collection.CloseableIterator
import org.locationtech.geomesa.utils.geotools.SimpleFeatureTypeLoader

val sft = SimpleFeatureTypeLoader.sftForName("outtype").getOrElse {
  throw new RuntimeException("Could not load feature type")
}
val conf = ConverterConfigLoader.configForName("myconverter").getOrElse {
  throw new RuntimeException("Could not load converter definition")
}
val converter = FeatureToFeatureConverter(sft, conf)
try {
  val features: Iterator[SimpleFeature] = ??? // list of input features to transform
  val iter = converter.convert(CloseableIterator(features))
  try {
    iter.foreach(???) // do something with the conversion result
  } finally {
    iter.close()
  }
} finally {
  converter.close() // clean up any resources associated with your converter
}