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Server Events

TomEE (through OpenEJB) fires internal events during its lifecycle, for example when the assembler has created an application. Any plain Java class can observe these events with a method whose parameter is annotated with org.apache.openejb.observer.Observes. Note that this is the OpenEJB observer API, not CDI’s jakarta.enterprise.event.Observes.

This example shows two ways to register such an observer:

  • as a service declared in the container configuration (MyListener)

  • as an extension discovered automatically from META-INF/org.apache.openejb.extension (AutoDiscoveredListener)

An observer registered as a service

MyListener observes Object, so it receives every event fired by the server and logs it. It also has a setter, which makes logAllEvent a property that can be set from the service configuration.

package org.superbiz.event;

import org.apache.openejb.observer.Observes;

import java.util.logging.Logger;

/**
 * registered as service in openejb.xml, tomee.xml, resources.xml or openejb system properties:
 *
 * listener = new://Service?class-name=org.superbiz.event.MyListener
 * listener.logAllEvent = true
 */
public class MyListener {

    private static final Logger LOGGER = Logger.getLogger(MyListener.class.getName());

    private static boolean logAllEvent = false; // static for testing

    public void global(@Observes final Object event) {
        LOGGER.info(">>> an event occurred -> " + event.toString());
    }

    // configurable
    public void setLogAllEvent(boolean logAllEvent) {
        this.logAllEvent = logAllEvent;
    }

    public static boolean isLogAllEvent() {
        return logAllEvent;
    }
}

As the Javadoc says, the class is not picked up on its own: it has to be declared as a service in openejb.xml, tomee.xml, resources.xml or as OpenEJB system properties:

listener = new://Service?class-name=org.superbiz.event.MyListener
listener.logAllEvent = true

An auto-discovered observer

AutoDiscoveredListener only observes AssemblerAfterApplicationCreated, the event fired once an application has been created, and stores the application id.

package org.superbiz.event;

import org.apache.openejb.assembler.classic.event.AssemblerAfterApplicationCreated;
import org.apache.openejb.observer.Observes;

public class AutoDiscoveredListener {

    private static String appName;

    public void appCreated(@Observes final AssemblerAfterApplicationCreated appCreatedEvent) {
        appName = appCreatedEvent.getApp().appId;
    }

    public static String getAppName() {
        return appName;
    }
}

It needs no service declaration. Instead, its fully qualified class name is listed in src/main/resources/META-INF/org.apache.openejb.extension:

org.superbiz.event.AutoDiscoveredListener

Testing

The test runs with the embedded OpenEJB Arquillian adapter (arquillian-openejb-embedded). src/test/resources/arquillian.xml registers MyListener as a service through the container properties:

<arquillian
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    >
  <container qualifier="openejb" default="true">
    <configuration>
      <property name="properties">
        listener = new://Service?class-name=org.superbiz.event.MyListener
        listener.logAllEvent = true
      </property>
    </configuration>
  </container>
</arquillian>

The deployment is a listener-test.jar that contains both listeners and an org.apache.openejb.extension manifest resource naming AutoDiscoveredListener:

@RunWith(Arquillian.class)
public class ListenerTest {

    @Deployment
    public static JavaArchive jar() {
        return ShrinkWrap.create(JavaArchive.class, "listener-test.jar")
                .addClasses(MyListener.class, AutoDiscoveredListener.class)
                .addAsManifestResource(new StringAsset(AutoDiscoveredListener.class.getName()), ArchivePaths.create("org.apache.openejb.extension"));
    }

    @Test
    public void check() {
        assertEquals("listener-test", AutoDiscoveredListener.getAppName());
        assertTrue(MyListener.isLogAllEvent());
    }
}

The test checks that:

  • AutoDiscoveredListener received the AssemblerAfterApplicationCreated event for the deployed application, whose id is listener-test

  • MyListener was created from the service configuration and its logAllEvent property was set to true

Run it with:

mvn clean test

APIs Used