16 Configuring Custom Spring Beans

16.1.1 Spring Bean Event Sources and Event Sinks

Standard Spring beans can be event sources, event sinks, or both. Event sources generate events, event sinks receive events.

<bean id="bean" class="com.acme.BeanSource" />

<wlevs:channel id="S2" advertise="true" event-type="StockEvent" >
    <wlevs:listener ref="bean"/>
    <wlevs:source ref="cacheProcessor"/>
</wlevs:channel>
 
<bean id="bean" class="com.bea.wlevs.example.cachecql.Bean" />

16.2.1 Implementing a Custom Spring Bean as an Event Source

The following example shows a custom Spring bean class as an event source ; see the explanation after the example for coding guidelines that correspond to the Java code in bold.

package com.acme;

import com.bea.wlevs.ede.api.StreamSender;
import com.bea.wlevs.ede.api.StreamSource;
import com.bea.wlevs.ede.api.RunnableBean;
 
public class SpringBeanSource implements RunnableBean, StreamSource {

    public void setEventSender (StreamSender streamSender) {
    ...
    }

    public void run() {
    ...
    }

    public synchronized void suspend() throws Exception {
    ...
    }
}

Follow these guidelines when programming the custom Spring bean Java class; code snippets of the guidelines are shown in bold in the preceding example:

• Import the interfaces and classes of the Oracle CEP API:

  import com.bea.wlevs.ede.api.StreamSender;
  import com.bea.wlevs.ede.api.StreamSource;
  import com.bea.wlevs.ede.api.RunnableBean;
  

  Because the custom Spring bean is an event source it must implement the StreamSource interface. If you want the custom Spring bean to run in a thread, also implement RunnableBean. The StreamSender interface sends event types to the next component in your application network. For full details of these APIs, see Oracle Fusion Middleware Java API Reference for Oracle Complex Event Processing.

• The custom Spring bean class must implement the StreamSource and RunnableBean interfaces because it is an event source and will run in its own thread:

  public class HelloWorldAdapter implements RunnableBean, StreamSource {
  

  The StreamSource interface provides the StreamSender that you use to send events.

• Because the custom Spring bean implements the RunnableBean interface, your adapter must then implement the run method:

  public void run() {...
  

  This is where you should put the code that reads the incoming data, such as from a market feed, and convert it into an Oracle CEP event type, and then send the event to the next component in the network. Refer to the documentation of your data feed provider for details on how to read the incoming data. See Section 24.2.2.2, "Accessing Third-Party JAR Files" for information about ensuring you can access the vendor APIs if they are packaged in a third-party JAR file.

• Because the custom Spring bean implements StreamSource, you must implement the setEventSender method, which passes in the StreamSender that you use to send events:

  public void setEventSender(StreamSender sender) { ...
  

• If, as is typically the case, your custom Spring bean implements SuspendableBean, you must implement the suspend method that stops the adapter when, for example, the application is undeployed:

  public synchronized void suspend() throws Exception { ... 
  

16.2.2 Implementing a Custom Spring Bean as an Event Sink

The following sample code shows a Spring bean from HelloWorld application that acts as an event sink; see the explanation after the example for the code shown in bold:

package com.bea.wlevs.example.helloworld;
 
import com.bea.wlevs.ede.api.StreamSink;
import com.bea.wlevs.event.example.helloworld.HelloWorldEvent;
 
public class HelloWorldBean implements StreamSink {
 
    public void onInsertEvent(Object event) {
        if (event instanceof HelloWorldEvent) {
            HelloWorldEvent helloWorldEvent = (HelloWorldEvent) event;
            System.out.println("Message: " + helloWorldEvent.getMessage());
        }   
    }
 
}

The programming guidelines shown in the preceding example are as follows:

• Your bean must import the event type of the application, which in the HelloWorld case is HelloWorldEvent:

  import com.bea.wlevs.event.example.helloworld.HelloWorldEvent;
  

• Your bean must implement the com.bea.wlevs.ede.api.StreamSink interface:

  public class HelloWorldBean implements StreamSink {...
  

• The StreamSink interface has a single method that you must implement, onInsertEvent(java.lang.Object), which is a callback method for receiving events. The parameter of the method is an Object that represents the actual event that the bean received from the component that sent it the event:

  public void onInsertEvent(Object event)
  

• The data type of the events is determined by the event type you registered in the EPN assembly file of the application. In the example, the event type is HelloWorldEvent; the code first ensures that the received event is truly a HelloWorldEvent:

  if (event instanceof HelloWorldEvent) {
      HelloWorldEvent helloWorldEvent = (HelloWorldEvent) event;
  

  This event type is a JavaBean that was configured in the EPN assembly file as shown:

  <wlevs:event-type-repository>
      <wlevs:event-type type-name="HelloWorldEvent">
         <wlevs:class>
           com.bea.wlevs.event.example.helloworld.HelloWorldEvent
         </wlevs:class>
      </wlevs:event-type>
  </wlevs:event-type-repository>
  

  See Section 4.3, "Creating EPN Assembly Files" for procedural information about creating the EPN assembly file, and Appendix C, "Schema Reference: EPN Assembly spring-wlevs-v11_1_1_3.xsd" for reference information.

• Events are instances of the appropriate JavaBean, so you access the individual properties using the standard getXXX methods. In the example, the HelloWorldEvent has a property called message. You access this property using method getMessage:

  System.out.println("Message: " + helloWorldEvent.getMessage());
  

For complete API reference information about the Oracle CEP APIs described in this section, see the Oracle Fusion Middleware Java API Reference for Oracle Complex Event Processing.

16.3.1 Declaring the Custom Spring Bean Components in your Application

In the EPN assembly file, you use the bean element to declare a custom Spring bean as a component in the event processor network. For example:

<bean id="recplayEventSink"
                  class="com.bea.wlevs.example.recplayRecplayEventSink">
</bean>