AbstractProcessManagerStatusPublisher.java

package org.springframework.roo.process.manager.event;

import java.util.Set;
import java.util.concurrent.CopyOnWriteArraySet;

import org.apache.commons.lang3.Validate;
import org.springframework.roo.process.manager.ProcessManager;

/**
 * Provides a convenience superclass for those {@link ProcessManager}s wishing
 * to publish status messages.
 * 
 * @author Ben Alex
 * @since 1.0
 */
public abstract class AbstractProcessManagerStatusPublisher implements ProcessManagerStatusProvider {

  /**
   * Used so a single object instance contains the changing
   * {@link ProcessManagerStatus} enum. This is needed so there is a single
   * object instance for synchronization purposes.
   */
  private static class StatusHolder {

    private ProcessManagerStatus status;

    /**
     * Constructor
     * 
     * @param initialStatus
     */
    private StatusHolder(final ProcessManagerStatus initialStatus) {
      status = initialStatus;
    }
  }

  protected StatusHolder processManagerStatus = new StatusHolder(ProcessManagerStatus.STARTING);

  protected Set<ProcessManagerStatusListener> processManagerStatusListeners =
      new CopyOnWriteArraySet<ProcessManagerStatusListener>();

  public final void addProcessManagerStatusListener(
      final ProcessManagerStatusListener processManagerStatusListener) {
    Validate.notNull(processManagerStatusListener, "Status listener required");
    processManagerStatusListeners.add(processManagerStatusListener);
  }

  /**
   * Obtains the process manager status without synchronization.
   */
  public final ProcessManagerStatus getProcessManagerStatus() {
    return processManagerStatus.status;
  }

  public final void removeProcessManagerStatusListener(
      final ProcessManagerStatusListener processManagerStatusListener) {
    Validate.notNull(processManagerStatusListener, "Status listener required");
    processManagerStatusListeners.remove(processManagerStatusListener);
  }

  /**
   * Set the process manager status without synchronization.
   */
  protected void setProcessManagerStatus(final ProcessManagerStatus processManagerStatus) {
    Validate.notNull(processManagerStatus, "Process manager status required");

    if (this.processManagerStatus.status == processManagerStatus) {
      // No need to make a change
      return;
    }

    this.processManagerStatus.status = processManagerStatus;

    for (final ProcessManagerStatusListener listener : processManagerStatusListeners) {
      listener.onProcessManagerStatusChange(this.processManagerStatus.status, processManagerStatus);
    }
  }

}