Java™ Operator API overview

You use the Teracloud® Streams Java™ Operator API to implement user-defined operators in Java™.

The Javadoc™ documentation for this API is provided with the Teracloud® Streams installation in the $STREAMS_INSTALL/doc/spl/operator/api/java/api directory. The primary package within this API iscom.ibm.streams.operator. Here is a brief description of its main classes.
  • Operator: This interface defines an operator. The Teracloud® Streams run time calls methods on this interface for initialization and then on for each incoming tuple and punctuation until a shutdown request is made.
  • AbstractOperator: Is an abstract class that developers can extend to implement Operator. It provides a number of useful utility methods.
  • OperatorContext: This interface provides access to the operator's runtime context, including descriptions of the streams and parameters. In addition, it provides access to a Java™ ScheduledExectorService and ThreadFactory for asynchronous actions.
  • StreamSchema: This interface describes the schema of a port, including the names and types (Java™ and SPL) of its attributes.
  • StreamingInput: This interface describes an input port, including its schema.
  • StreamingOutput: This interface describes an output port and provides methods to obtain new output tuples and to submit them.
  • Tuple: This interface implements an immutable object that generically represents an incoming tuple.
  • OutputTuple: This interface implements a mutable object that generically represents an outgoing tuple.
The Java™ Operator API is in the Teracloud® Streams library com.ibm.streams.operator.jar, which is located in $STREAMS_INSTALL/lib. The Java™ Operator API depends on Apache Commons Math 2.2 library (commons-math-2.2.jar) which is located in $STREAMS_INSTALL/ext/lib. When you develop Java™ operators using the Java™ Operator API, the com.ibm.streams.operator.jar and commons-math-2.2.jar libraries are required in the class path. Sample operators and patterns, including source, are supplied in the Teracloud® Streams Version 7.2.0 library com.ibm.streams.operator.samples.jar, which is in $STREAMS_INSTALL/lib.
Note: All of these libraries are automatically added by the Teracloud® Streams run time for operator invocation, thus they must not be declared as dependencies of a Java™ primitive operator or included in the classLibrary parameter for a JavaOp invocation.

The Teracloud® Streams run time provides a Java™ SE Version 8 execution environment for operators that are implemented using the Teracloud® Streams Java™ Operator API. The virtual machine that is used by a stream application is defined by the setting of the environment variable JAVA_HOME when the SPL compiler (sc) is run.