To hand over values from an XPage to a custom control, which approach should be used ? a) Define properties in the custom control at design time. Fill in the properties at the XPage with computed values. Use the value via 'compositeData' in the custom control at runtime. or b) Put the value in a session scope variable at the XPage in BeforePageLoad event. Bind the session scope variable to the field in the custom control.
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1 Answers
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The session scope is primarily intended for ensuring that values persist as the user navigates between pages. I like to call it the "shopping cart" scope: if you built an e-commerce site in Domino, you wouldn't want the site to forget that a user had added a product to their cart just because they clicked back to the home page. So this scope is also useful for features like remembering search / sort / filter options as the user navigates the app so each time they navigate somewhere else and come back, it remembers their prior behavior without having to store this information permanently in the NSF.
For passing in-page information to a Custom Control from a container, however, compositeData is definitely the way to go. This is because that variable is populated with the passed parameters only for the duration of the processing of the relevant control. Once that control has been dealt with, all pointers to the passed parameters are cleaned up automatically, which provides incremental scalability improvement for each instance compared to storing the same information for the duration of each user's session.
There will be cases where there is overlap: a given Custom Control might reference information that is appropriate to store in the session scope. In this scenario I like to mix the two techniques... for example:
<xp:inputText value="#{sessionScope[compositeData.scopeKey]}" />
The above syntax allows a Custom Control to be passed by its container the identifier for where in the session scope the relevant information is stored. This provides some serious flexibility, because I can drop the same control into multiple contexts, with each telling the control which information it should retrieve / store in scope.
