Respond to Create Channel and Update Channel Settings Events

Overview

This page describes how to implement custom logic that executes when a user creates a channel or updates a channel's settings in Bloomreach Content.

When to Use

Implement a ChannelManagerEventListener when you need to trigger custom logic in response to channel creation or channel settings updates. Common use cases include:

Logging channel lifecycle events
Synchronizing external systems when channels change
Enforcing additional business rules on channel configuration

ChannelManagerEventListener Interface

The HST API provides the org.hippoecm.hst.configuration.channel.ChannelManagerEventListener interface. This interface defines two callback methods:

void channelCreated(ChannelManagerEvent event)
Invoked immediately after a channel is created from a blueprint.
void channelUpdated(ChannelManagerEvent event)
Invoked immediately after a channel's settings are updated.

You can register multiple implementations of ChannelManagerEventListener in your project. When a channel is created or updated, the corresponding callback method is called on each registered listener.

To activate your listener, register it as a Spring bean. See the Spring Configuration example below.

Example Implementation

The following example demonstrates a ChannelManagerEventListener that logs information about channel creation and update events. This implementation is part of the Hippo Test Suite.

Implementation Class

hippo-testsuite/components/src/main/java/org/hippoecm/hst/demo/channel/DemoChannelManagerEventListener.java

/**
 * DemoChannelManagerEventListener
 * <P>
 * Example <CODE>ChannelManagerEventListener</CODE> implementation
 * which simply logs all the triggered event information.
 * </P>
 */
public class DemoChannelManagerEventListener
            implements ChannelManagerEventListener {

    private static Logger log =
            LoggerFactory.getLogger(DemoChannelManagerEventListener.class);

    public void channelCreated(ChannelManagerEvent event) {
        log.info("A channel has been created. {}",
                 channelManagerEventToString(event));
    }

    public void channelUpdated(ChannelManagerEvent event) {
        log.info("A channel has been updated. {}",
                 channelManagerEventToString(event));
    }

    private String channelManagerEventToString(ChannelManagerEvent event) {
        StringBuilder sb = new StringBuilder(100);
        sb.append("{ ");

        Blueprint blueprint = event.getBlueprint();
        // blueprint can be null
        if (blueprint != null) {
            sb.append("blueprint: [ ");
            sb.append(blueprint.getId()).append(", ");
            sb.append(blueprint.getName()).append(", ");
            sb.append(blueprint.getDescription());
            sb.append(" ], ");
        }

        Channel channel = event.getChannel();
        // channel will never be null
        sb.append("channel: [ ");
        sb.append(event.getChannel().getId()).append(", ");
        sb.append(channel.getName()).append(", ");
        sb.append(channel.getContentRoot());
        sb.append(" ], ");

        Node configRootNode = event.getConfigRootNode();

        try {
            if (configRootNode != null) {
                sb.append("configRootNode: ");
                sb.append(configRootNode.getPath());
            }
        } catch (RepositoryException e) {
            log.error("Failed to read channel node path", e);
        }

        sb.append(" }");
        return sb.toString();
    }
}

Spring Configuration

hippo-testsuite/components/src/main/resources/META-INF/hst-assembly/overrides/channelManagerListenerExample.xml

  <!-- Custom channel manager event listeners in the following may be
       overriden in their project specific assembly. -->
  <bean id="customChannelManagerEventListeners"
        class="org.springframework.beans.factory.config.ListFactoryBean">
    <property name="sourceList">
      <list>
        <bean class=
             "org.hippoecm.hst.demo.channel.DemoChannelManagerEventListener">
        </bean>
      </list>
    </property>
  </bean>

Verification

After registering your listener and deploying your project, create or update a channel in the Experience manager. Verify that your custom logic executes as expected (for example, check the logs for output from your listener).