Channel Processor Components of the Oracle CEP Event Processing Network

1-4 Oracle Complex Event Processing Developers Guide ■ Section 11.3, Configuring an EPL Processor Cache Source ■ Chapter 12, Configuring Caching .

1.1.1.7 Table

A table is a component that connects a relational database table to the EPN as an event data source. You can access a relational database table from an Oracle CQL query using: ■ table source: using a table source, you may join a stream only with a NOW window and only to a single database table. For more information, Section 10.3, Configuring an Oracle CQL Processor Table Source . ■ Oracle JDBC data cartridge: using the Oracle JDBC data cartridge, you may integrate arbitrarily complex SQL queries and multiple tables and datasources with your Oracle CQL queries. For more information, see Understanding the Oracle JDBC Data Cartridge in the Oracle Complex Event Processing CQL Language Reference. In all cases, you must define datasources in the Oracle CEP server config.xml file. For more information, see Configuring Access to a Relational Database in the Oracle Complex Event Processing Administrators Guide. Oracle CEP relational database table event sources are pull data sources: that is, Oracle CEP will periodically poll the event source.

1.1.1.8 Nested Stages

When you define a child stage within a parent stage in an EPN, the child stage is said to be nested. Only the parent stage can specify the child stage as a listener. Example 1–1 shows the EPN assembly source in which HelloWorldBean is nested within the helloworldOutputChannel. Only the parent helloworldOutputChannel may specify the nested bean as a listener. Example 1–1 EPN Assembly File With Nested Bean wlevs:adapter id=helloworldAdapter class=com.bea.wlevs.adapter.example.helloworld.HelloWorldAdapter wlevs:instance-property name=message value=HelloWorld - the current time is: Note: Because changes in the table source are not coordinated in time with stream data, you may only join the table source to an event stream using a Now window and you may only join to a single database table. For more information, see S[now] in the Oracle Complex Event Processing CQL Language Reference. To integrate arbitrarily complex SQL queries and multiple tables with your Oracle CQL queries, consider using the Oracle JDBC data cartridge instead. Note: Oracle recommends that you use the Oracle JDBC data cartridge to access relational database tables from an Oracle CQL statement.