The Esper development team is proud to announce the release of Esper 1.0 final. Esper is an event stream processing (ESP) and event correlation engine (CEP) written in Java.

A more complete description of the project goals and history has been published on InfoQ.

Esper is open-source software available under the LPGL license.
Please visit Esper at Codehaus for tutorial, case studies and downloads.

Esper is well suited for real-time event driven applications. It performs grouping, aggregation, sorting, filtering, merging and joining of event streams using a tailored SQL-like query language. Applications can define time-based, interval-based, length-based and sorted windows and perform inner-joins and outer joins of an unlimited number of windows and event streams. Esper also performs complex event pattern matching allowing logical and temporal event correlation.

A primary difference with systems relying on classical SQL databases is that events are not stored and later on polled in a massive hence underperformant repository. Instead as the flow of events come matching registered event conditions, Esper triggers customized registered actions (POJO) - hence drastically reducing the latency.