9.17. 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.

9.17.1. Configuration

The feature-to-feature converter supports the following configuration keys:

Key	Required	Type	Description
type	yes	String	Must be the string simple-feature.
input-sft	yes	String	Name of a feature type available on the classpath.

9.17.1.1. input-sft

The input feature type must 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.

9.17.2. Transform Functions

The attributes of the input feature type can be accessed by transforms, using $ notation. Note that the input feature type will take precedence over any converter fields when resolving attribute references. 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.

9.17.3. 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.convert2.simplefeature.FeatureToFeatureConverter
import org.locationtech.geomesa.utils.collection.CloseableIterator

val converter = FeatureToFeatureConverter("outtype", "myconverter")
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
}