Xpages bean vs object data

Question

What's the difference? When should I prefer one over another?

And some minor questions related to this:

• if I have object data, when is saveObject called?

• it looks like garbage collector recycles all my domino handles. I tried to downcast then clone it, but it didn't help (how does it know its still a domino object?). Is there a workaround?

• if I create "var tmpVar = new package.TestClass()" from xPages, it gets recycled on update. But if I create java object from bean it stays there. Correct?

Answer 1

Managed beans are exactly that, managed by the XPages runtime. They are created as and when there is a first call to them. Although they have an empty constructor, managed-properties elements in the faces-config allow you to define values (and I believe you can add SSJS code to the faces-config to compute the values).

Object data sources allow you to handle what's created when, and it means they can be scoped to a smaller level than viewScope - to a Panel or Custom Control. The saveObject method is called by a Save All Datasources event. In reality, if you're coding object data sources, you'll code a button and call the relevant method rather than use a simple action.

Java variables can get recycled, but Domino objects are only recycled via two methods. The first is calling recycle() methods, the second is at the end of each request, when the session gets recycled. Because recycle() calls recycle all child elements, everything gets recycled at the end of a request. Which is why you can't store Domino objects in scoped variable or any other persisted object (i.e. a bean). Note that objects like DateTimes, RichTextStyles etc are children of the session, not of any more granular Domino object like a NotesItem or NotesRichTextItem.

var tmpVar = new package.TestClass() will only get persisted beyond the current request if you store tmpVar somewhere. If you're using that code in a crerateObject method, return tmpVar will pass that instance of TestClass into the Data Object.