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From D Tim Cummings <>
Subject How to link to user record who made changes in audit trail
Date Sun, 20 Jul 2014 06:23:59 GMT
Hi all

I want to set up a simple audit trail which basically links who was the person to create a
record to that record. I am using Cayenne 3.2M1 and Tapestry 5.3.7. I figure I need to set
up a data channel filter to catch changes to that record and then save a link to the user
who made the change. 

The problem is, if I save the user in the data channel filter object when someone logs in,
then all created records link to the last logged in user. 

If I save the user in a ThreadLocal in the data channel filter object, I get a different user
each time (often blank) because the data channel filter seem to run in its own thread which
changes each time.

I have been watching the excellent and now freely available podcast by Andrus Adamchik presented
to WebObjects developers "Advanced Apache Cayenne" where he talks about lifecycle events,
(callbacks, listeners), caching, data channel filters, clustering, in cayenne 3.2M1.
In Andrus's sample code he uses AuditableProcessor, but I couldn't think how to use it to
solve this problem.

Here is a copy of my listener/data channel filter with the ThreadLocal code.



public class AuditListener implements DataChannelFilter {
  private static final Logger logger = LoggerFactory.getLogger(AuditListener.class);
  private ThreadLocal<Integer> tlUserId;

  void doPrePersist(DataObject object) {
    if ( object instanceof AuditableCreateCancel ) {
      AuditableCreateCancel acc = (AuditableCreateCancel) object;
      TblPerson user = getTheUser(object.getObjectContext());
  private TblPerson getTheUser(ObjectContext oc) {
    Thread t = Thread.currentThread();
    Integer idUser = tlUserId.get();
    if ( idUser == null ) {"Thread " + t.getId() + " idUser == null ");
      return null;
    }"Thread " + t.getId() + " Looking for TblPerson " + idUser);
    TblPerson p = Cayenne.objectForPK(oc, TblPerson.class, idUser.intValue());
    return p;

  public void init(DataChannel channel) {
    tlUserId = new ThreadLocal<Integer>();

  public QueryResponse onQuery(ObjectContext originatingContext, Query query, DataChannelFilterChain
filterChain) {
    return filterChain.onQuery(originatingContext, query);

  public GraphDiff onSync(ObjectContext originatingContext, GraphDiff changes, int syncType,
DataChannelFilterChain filterChain) {
    try {
      return filterChain.onSync(originatingContext, changes, syncType);
    } finally {
  public void setTheUserId(int idUser) {
    Thread t = Thread.currentThread();"Thread " + t.getId() + " setTheUserId " + idUser);

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