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From: D Tim Cummings <tim@triptera.com.au>
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Subject: How to link to user record who made changes in audit trail
Message-Id: <090A08F2-A812-4762-899F-2A4CBDA61EFF@triptera.com.au>
Date: Sun, 20 Jul 2014 16:23:59 +1000
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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.=20

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.=20

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.
https://itunes.apple.com/podcast/webobjects-podcasts/id270165303?mt=3D2#
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.

Thanks=20

Tim


public class AuditListener implements DataChannelFilter {
 =20
  private static final Logger logger =3D =
LoggerFactory.getLogger(AuditListener.class);
 =20
  private ThreadLocal<Integer> tlUserId;

  @PrePersist(entityAnnotations=3DTagCreateCancel.class)
  void doPrePersist(DataObject object) {
    if ( object instanceof AuditableCreateCancel ) {
      AuditableCreateCancel acc =3D (AuditableCreateCancel) object;
      TblPerson user =3D getTheUser(object.getObjectContext());
      acc.setTblPersonCreate(user);
    }
  }
 =20
  private TblPerson getTheUser(ObjectContext oc) {
    Thread t =3D Thread.currentThread();
    Integer idUser =3D tlUserId.get();
    if ( idUser =3D=3D null ) {
      logger.info("Thread " + t.getId() + " idUser =3D=3D null ");
      return null;
    }
    logger.info("Thread " + t.getId() + " Looking for TblPerson " + =
idUser);
    TblPerson p =3D Cayenne.objectForPK(oc, TblPerson.class, =
idUser.intValue());
    return p;
  }

  @Override
  public void init(DataChannel channel) {
    tlUserId =3D new ThreadLocal<Integer>();
  }

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

  @Override
  public GraphDiff onSync(ObjectContext originatingContext, GraphDiff =
changes, int syncType, DataChannelFilterChain filterChain) {
    try {
      return filterChain.onSync(originatingContext, changes, syncType);
    } finally {
      //
    }
  }
 =20
  public void setTheUserId(int idUser) {
    Thread t =3D Thread.currentThread();
    logger.info("Thread " + t.getId() + " setTheUserId " + idUser);
    tlUserId.set(Integer.valueOf(idUser));
  }
 =20
}


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