Defining streams

Apama Documentation : Developing Apama Applications : Developing Apama Applications in EPL : Working with Streams and Stream Queries : Defining streams

Defining streams

Creating streams from event templates

Terminating streams

You can use a stream variable to reference a stream. A stream variable declaration has the following form:

stream<type> name

Replace type with the type of the items in the stream. This can be any Apama type.

Replace name with an identifier for the stream. For example:

stream<Tick> ticks;

A stream variable can be a field in an event. However, you cannot route, enqueue, or send an event that contains a stream variable field.

There are two ways to create a stream:

From an event template. See Creating streams from event templates.

From the result of a stream query on some other stream. See Defining stream queries.

To obtain a reference to an existing stream, you must assign from or clone another stream value.

An inert stream never generates any output. There are a number of ways to create an inert stream including, but not limited to, the following:

Calling new on a stream type or a type that contains a stream

Declaring a global variable of stream type, or a type that contains a stream

Spawning a monitor instance that contains a stream value

Note:

It is permissible to define a stream variable that references a stream of stream type items. In such a definition, be sure to insert a space between the consecutive right-angle brackets. For example: stream<stream<float> >. You must insert this extra space in all stream definitions that contain a type that encloses another type. For example: stream<sequence<integer> >.

Contact Support | Community | Feedback