InheritableThreadLocalPentahoSessionHolderStrategy.java

package org.pentaho.platform.engine.core.system;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.pentaho.platform.api.engine.IPentahoSession;
import org.pentaho.platform.engine.core.messages.Messages;

/**
 * An {@code InheritableThreadLocal}-based implementation of {@link IPentahoSessionHolderStrategy}.
 * 
 * @author mlowery
 */
public class InheritableThreadLocalPentahoSessionHolderStrategy implements IPentahoSessionHolderStrategy {

  // ~ Static fields/initializers ======================================================================================

  private static final Log logger = LogFactory.getLog(InheritableThreadLocalPentahoSessionHolderStrategy.class);

  // ~ Instance fields =================================================================================================

  private static final ThreadLocal<IPentahoSession> perThreadSession = new InheritableThreadLocal<IPentahoSession>();

  // ~ Constructors ====================================================================================================

  public InheritableThreadLocalPentahoSessionHolderStrategy() {
    super();
  }

  // ~ Methods =========================================================================================================

  /**
   * Sets an IPentahoSession for the current thread
   * @param session
   */
  public void setSession(IPentahoSession session) {
    perThreadSession.set(session);
  }

  /**
   * Returns the IPentahoSession for the current thread
   * @return thread session
   */
  public IPentahoSession getSession() {
    IPentahoSession sess = perThreadSession.get();
    if (sess == null) {
      //In a perfect world, the platform should never be in a state where session is null, but we are not there yet.  Not all places
      //that instance sessions use the PentahoSessionHolder yet, so we will not make a fuss here if session is null.  When PentahoSessionHolder
      //is fully integrated with all sessions, then we should probably throw an exception here since in that case a null session means 
      //the system is in an illegal state.
      logger.debug(Messages.getInstance().getString(
          "PentahoSessionHolder.WARN_THREAD_SESSION_NULL", Thread.currentThread().getName())); //$NON-NLS-1$
    }
    return sess;
  }

  /**
   * Removes the IPentahoSession for the current thread.
   * It is important that the framework calls this to prevent session bleed-
   * through between requests as threads are re-used by the server.
   */
  public void removeSession() {
    IPentahoSession sess = perThreadSession.get();

    if (sess != null) {
      if (logger.isDebugEnabled()) {
        logger.debug(Messages.getInstance().getString("PentahoSessionHolder.DEBUG_REMOVING_SESSION",//$NON-NLS-1$
            Thread.currentThread().getName(), String.valueOf(Thread.currentThread().getId())));
      }
      if (logger.isTraceEnabled()) {
        StackTraceElement[] elements = Thread.currentThread().getStackTrace();
        logger.trace(Messages.getInstance().getString("PentahoSessionHolder.DEBUG_THREAD_STACK_TRACE"));//$NON-NLS-1$
        for (int i = 0; i < elements.length; i++) {
          logger.trace(elements[i]);
        }
      }

      //If the session is a custom/stand-alone session, we need to remove references
      //to it from other objects which may be holding on to it.  We do this to prevent
      //memory leaks.  In the future, this should not be necessary since objects
      //should not need to have setSesssion methods, but instead use PentahoSessionHolder.getSession()
      if (sess instanceof StandaloneSession) {
        if (logger.isDebugEnabled()) {
          logger.debug(Messages.getInstance().getString("PentahoSessionHolder.DEBUG_DESTROY_STANDALONE_SESSION",//$NON-NLS-1$
              String.valueOf(sess.getId()), sess.getName(), String.valueOf(Thread.currentThread().getId())));
        }
        ((StandaloneSession) sess).destroy();
      }

      perThreadSession.remove();
    }
  }

}