root package

Scala application support for IBM Streams

Overview

Applications are written in Scala for IBM Streams by using the Java Application API classes and methods.

Importing com.ibm.streamsx.topology.functions.FunctionConversions, allows Scala functions to be used as functions used to transform, filter tuples etc.

import com.ibm.streamsx.topology.functions.FunctionConversions._

Here's a simple example (simple.FilterEchoScala) that filters a stream created from the command line arguments so that it only includes values that being with d.

package simple;

import com.ibm.streamsx.topology.TStream;
import com.ibm.streamsx.topology.Topology;
import com.ibm.streamsx.topology.context.StreamsContextFactory;

// Implicit conversions of Scala anonymous functions
// to functions for the Java Application API
import com.ibm.streamsx.topology.functions.FunctionConversions._

object FilterEchoScala {
  def main(args: Array[String]) {
    val topology = new Topology("FilterEchoScala")

    var echo = topology.strings(args:_*)

    echo = echo.filter((v:String) => v.startsWith("d"))

    echo.print()

    StreamsContextFactory.getStreamsContext("EMBEDDED").submit(topology).get()
  }
}

Samples

Sample Scala applications are under samples/scala.

Details

The version of Scala used is defined by the value of the environment variable SCALA_HOME. When a IBM Streams application bundle is created, then $SCALA_HOME/lib/scala-library.jar is copied into the Streams application bundle for use during application execution.

These libraries must be added to the Scala classpath for compilation and execution:

com.ibm.streamsx.topology/lib/com.ibm.streamsx.topology.jar - Scala & Java Application APIs for IBM Streams

$STREAMS_INSTALL/lib/com.ibm.streams.operator.samples.jar - IBM Streams Java Operator API and its samples

When compiling with scalac the flag -usemanifestcp is required.