20.17. Extending the Converter Library

There are two ways to extend the converter library - adding new transformation functions and adding new data formats.

20.17.1. Adding Scripting Functions

The easiest way to extend functionality is by defining custom Javascript functions. See Functions defined using scripting languages for more details.

20.17.2. Adding New Transformation Functions

To add new transformation functions, create a TransformationFunctionFactory and register it in META-INF/services/org.locationtech.geomesa.convert2.transforms.TransformerFunctionFactory. For example, here’s how to add a new transformation function that computes a SHA-256 hash.

import org.locationtech.geomesa.convert2.transforms.TransformerFunctionFactory
import org.locationtech.geomesa.convert2.transforms.TransformerFunction

class SHAFunctionFactory extends TransformerFunctionFactory {
  override def functions = Seq(sha256fn)
  val sha256fn = TransformerFunction("sha256") { args =>
    Hashing.sha256().hashBytes(args(0).asInstanceOf[Array[Byte]])
  }
}

The sha256 function can then be used in a field as shown.

fields: [
   { name = "hash", transform = "sha256(stringToBytes($0))" }
]

20.17.3. Adding New Data Formats

To add new data formats, implement the SimpleFeatureConverterFactory and SimpleFeatureConverter interfaces and register them in META-INF/services appropriately. See org.locationtech.geomesa.convert.text.DelimitedTextConverter for an example.

20.17.4. Adding Functions to the Geomesa Classpath

After creating a JAR file with your transformation function and factory you can add these to the GEOMESA_EXTRA_CLASSPATHS environmental variable in order to expose them to the command line tools and distributed (map-reduce) ingest jobs.

A example of ingest with a transforms on the classpath is below:

GEOMESA_EXTRA_CLASSPATHS="/tmp/custom-transformer-1.0.0.jar" bin/geomesa-accumulo ingest -u <user-name>
-p <password> -s <sft-name> -C <converter-name> -c geomesa.catalog hdfs://localhost:9000/data/example.csv

You can also verify the classpath is properly configured with the tools:

GEOMESA_EXTRA_CLASSPATHS="/tmp/custom-transformer-1.0.0.jar" bin/geomesa-accumulo classpath