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From "Mike Kienenberger" <mkien...@gmail.com>
Subject Re: Determining changes in a dataobject / modification diff
Date Fri, 22 Feb 2008 22:01:18 GMT
There's an issue in the Cayenne tracker that contains patches against
Cayenne 2.0 I've used to do this in the past:

https://issues.apache.org/cayenne/browse/CAY-414

I've done it by creating custom accessors like Robert Zeigler suggests
in my cayenne Entity templates as well, but I think the patch is
easier to maintain.


On Fri, Feb 22, 2008 at 11:41 AM, Andrus Adamchik
<andrus@objectstyle.org> wrote:
> One more way of doing that, based on the internal Cayenne mechanism
>  for tracking all object changes as instances of GraphDiff:
>
>    http://cayenne.apache.org/doc20/api/cayenne/org/apache/cayenne/graph/GraphDiff.html
>
>  There is no public API to access the diffs directly, but you can
>  intercept and process diffs on commit. Normally a
>  DataContext.getChannel() would return a DataDomain. A user can replace
>  it with a wrapper (via 'context.setChannel(..)') that delegates all
>  DataChannel operations to the DataDomain:
>
>    http://cayenne.apache.org/doc20/api/cayenne/org/apache/cayenne/DataChannel.html
>
>  In the wrapper you can override 'onSync' to analyze/capture all the
>  diffs being sent to the DataDomain for commit.
>
>  Andrus
>
>
>
>
>
>
>  On Feb 22, 2008, at 6:09 PM, Robert Zeigler wrote:
>  > Hi,
>  >
>  > I had a requirement very similar to this in a recent project.
>  > Every change made to a set of objects had to be recorded to be able
>  > to provide a history of changes to an object.
>  > What I did was to have those objects descend from a common super
>  > class, which, in turn, descends from CayenneDataObject.
>  > In my superclass, I overrode writeProperty and setToOneTarget.  You
>  > get the new values passed into you, and you have a chance to examine
>  > the old values, as well, by calling readProperty.  It has worked out
>  > quite nicely.
>  >
>  > Here's a sample snippet from writeProperty:
>  >
>  >    @Override
>  >    public void writeProperty(String name, Object value){
>  >        Object old = readProperty(name);
>  >        if (value == null) {
>  >            if (old != null) {
>  >                recordChange(name,name + " changed from " +
>  > labelFor(readProperty(name)) + " to " + labelFor(value));
>  >            }
>  >        } else if (!value.equals(old)) {
>  >                recordChange(name,name + " changed from " +
>  > labelFor(readProperty(name)) + " to " + labelFor(value));
>  >        }
>  >        super.writeProperty(name, value);
>  >    }
>  >
>  > recordChange handles recording the changes for me; labelFor takes an
>  > object and converts it into a string suitable for user consumption.
>  >
>  > HTH,
>  >
>  > Robert
>  >
>  > On Feb 22, 2008, at 2/228:59 AM , Ilya Lazarev wrote:
>  >
>  >> Apologies if this has been asked before, I couldn't find anything
>  >> in the
>  >> archives. The problem boils down to this: there is a cayenne object
>  >> which is
>  >> updated via a form. I want to capture changes made to every single
>  >> modified
>  >> field in a DB, the value before modification and the value after.
>  >> The object
>  >> has a number of to-many relationships, which would also have to be
>  >> checked
>  >> one by one. The simplest way I can envision this is by manually
>  >> creating an
>  >> object clone before any modifications are made, and then comparing
>  >> the two
>  >> objects and noting the differences. Is there an easier way to see a
>  >> diff of
>  >> the fields, perhaps by accessing properties of the cayenne object
>  >> itself? I
>  >> am using cayenne 2.
>  >>
>  >> Many thanks,
>  >> Ilya
>  >
>  >
>
>

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