Adding Custom Code

Siddhi supports custom codes within queries.

In the current implementation Windows and Aggregators are implemented in a pluggable manner.

Writing a custom Window

To write a custom window you have to create a class in the package "org.wso2.siddhi.core.query.stream.handler.window" with a name <Name>WindowHandler, and it has to extend "org.wso2.siddhi.core.query.stream.handler.window.WindowHandler".

You need to compile that class and add the jar to the class path. (In WSO2 CEP add that to the CEP_HOME/repertory/components/lib)

E.g for creating firstUnique window you class name need to be FirstUniqueWindowHandler.

You can use your class in the query as follows

from StockExchangeStream[price >= 20]#window.firstUnique(50) 
insert into StockQuote symbol, price

Writing a custom Aggregator

To write a custom aggregator you have to create a class in the package "org.wso2.siddhi.core.query.projector.attibute.processor" with a name <Name>AggregateAttributeProcessor, and it has to extend "org.wso2.siddhi.core.query.projector.attibute.processor.AbstractAggregateAttributeProcessor". This will work as the base class for aggregator creation.

Then you also need to create appropriate runtime aggregators implementing "org.wso2.siddhi.core.query.projector.attibute.aggregator.Aggregator" which will be specific for attribute types, such as  STRING, INT, LONG, FLOAT, DOUBLE & BOOL.

You need to compile these classes and add the jars to the class path. (In WSO2 CEP add them to the CEP_HOME/repertory/components/lib)

E.g for creating std Aggregator you need to create a class with name StdAggregateAttributeProcessor, and some appropriate Aggregators.

You can use your class in the query as follows

from StockExchangeStream[price >= 20]#window.length(50) 
insert into StockQuote symbol, std(price) as stdPrice