Delta Links

Use

The PCD provides delta link information about objects, such as whether the object is a delta link, what attributes were changed, and what attributes were erased.

Most information is derived from an IDlModificationState object that you can derive from the IPcdContext interface, as follows:

            Hashtable env = new Hashtable();
 
env.put(Context.INITIAL_CONTEXT_FACTORY,
         IPcdContext.PCD_INITIAL_CONTEXT_FACTORY);
env.put(Context.SECURITY_PRINCIPAL, request.getUser());
env.put(Constants.REQUESTED_ASPECT, IPcdAttribute.PERSISTENCY_ASPECT);
 
InitialContext   iCtx = null;
 
String lookupObject = "portal_content/myFolder/myObject";
 
try {
    iCtx = new InitialContext(env);
 
    IPcdContext myPcdContext =(IPcdContext) iCtx.lookup(lookupObject);
         
    IDlModificationState myDLState = myPcdContext
        .getDlModificationState("");
}

If the object is not a delta link or inherited via a delta link, getDlModificationState() returns null.

Getting Delta Link Information

From an IDlModificationState object, you can perform the following tasks:

  • Get the source object of a delta link.

                         response.write(myDLState.getSourceUrl());

  • Get all attributes that were changed in a delta link.

                         Iterator myMods = myDLState.getModifiedAttributeIds();
while (myMods.hasNext()) {
    response.write("ID: " + myMods.next() + "<BR>");
}

  • Get the changes made to a specific attribute of a delta link.

                         ModificationItem[] myMod =
    myDLState.getModifications("ForcedRequestLanguage");
 
for (int i=0;i<myMod.length;i++){
    response.write(myMod[i].getAttribute().getID()+"<BR>");
    response.write(myMod[i].getModificationOp()+"<BR>");
}

    The getModificationOp() method returns one of the following constants:

    • DirContext.ADD_ATTRIBUTE

    • DirContext.REMOVE_ATTRIBUTE

    • DirContext.REPLACE_ATTRIBUTE

    For each attribute, a delta link stores all the changes made to the attribute, not just the final result.

Creating a Delta Link

The following creates a delta link:

               Hashtable env = new Hashtable();
 
env.put(Context.INITIAL_CONTEXT_FACTORY,
    IPcdContext.PCD_INITIAL_CONTEXT_FACTORY);
env.put(Constants.REQUESTED_ASPECT, IPcdAttribute.PERSISTENCY_ASPECT);
env.put(Context.SECURITY_PRINCIPAL, request.getUser());
 
InitialContext iCtx = null;
String myFolderName = "pcd:portal_content/myFolderB";
 
try {
    iCtx = new InitialContext(env);
 
    IPcdContext myFolderB = (IPcdContext) iCtx.lookup(myFolderName);
 
    myFolderB.createDeltaLink(
        "myDL",null,"portal_content/myFolderA/myIView");
}
catch (Exception e) {}

The above creates a PCD object called myDL in myFolderB , which is a delta link to myIView in myFolderA .

Resetting Attributes

The following resets all attributes changed in a delta link object:

               myPcdContext.removeModifications("");

The following resets a specific attribute ( ForcedRequestLanguage ) that was changed in a delta link object:

               String myAttrsToDelete[] = {"ForcedRequestLanguage"};
               myPcdContext.removeAttributeModifications("",myAttrsToDelete);