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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?

Pang
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Ermo
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2 Answers2

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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.

Paul Stephen Withers
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I go back and forth on pure Managed Beans vs. Data Object. I was using a lot of Data Objects for a while but then ran into some issue with the JSF lifecycle I think that I just couldn't make work. Not sure if a repeat or custom control was involved. So I pretty much have gone back and given up on them for now.

Other then that problem I had I'm not sure there's a ton of difference. I think dataObject can tend to be a little more confusion. Since you can set it on an XPage - but you can change the scope of it to session or application I believe. But if you do then that seems messier and hard to find then making the bean in the faces-config.

I'm not sure about the saveObject part of your question.

You never want to put a pure domino object inside a bean, or scoped variable because they are not serializable and will be tossed by the garbage collector at some point that will likely be most inconvenient to you.

if you just do "var tmpVar = new package.TestClass()" then yeah that will get killed pretty quick because of limited life of that variable. if you want to create an object that way and keep it around longer put it in a true scope: viewScope.put("myObject", tmpVar);

I have a video where I tried to give examples of I think 4 ways to use java Objects. In the blog posting are some really good comments by Tim Tripcony which might give you further information.

http://www.notesin9.com/2013/08/01/notesin9-122-working-with-java-objects-in-xpages/

David Leedy
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