What is the flow of contollers load/execution in a Web Dynpro applicatio

Question

Hi Frndz..
As we now that we have the controllers in WDP like
1)Component contriller 2)CustomControoler 3) View Controller 4)Interface Controller 5) Interface view Controller.
Now i want to know what is the flow of thse controllers will load and execute when we run an Web Dynpro app.

Answer 1

Hi Rajesh
In general, dependent nodes are represented by a single node instance, whose content - that is, its node collection - changes each time the lead selection of the parent node changes. Such context nodes are known as single nodes.
This means that the user can only access data of the child nodes that belong to the code element (lead selection) currently selected in the parent node. Therefore, Web Dynpro allows you to define additional non-singleton nodes. Each non-singleton node has one node instance for each node element of the parent collection at runtime.
The advantage is that each instance can be accessed directly. When using non-singleton nodes, the nodes are only created when the node values are retrieved. This can save resources that otherwise would slow down the performance of the application.
Note that singleton nodes should only be considered singleton in relation to their parent nodes but not in relation to the context. Each instance of a non-singleton parent node has exactly one instance of the singleton node.
The singleton property can be defined for all dependent context nodes. It is either true or false:
-         singleton = true: Newly defined context nodes are of type singleton by default. This means that a child node instances exists for each parent node, not for each node element in the parent node. The content of the child node, that is, the list of the node elements it contains, changes each time the lead selection of the parent node changes.
-         singleton = false: A child node instance exists for each node element in the parent node. The content of this node instance does not change. The node instances of the child node can be accessed using generated context interfaces.
The varying relation between child and parent nodes is important for singleton and non-singleton nodes. Whereas singleton nodes are related to the parent node, non-singleton nodes always refer to a node element of the parent node at runtime.
Child nodes of type Singleton  always refer logically to an element of the parent node, that is, the one in the lead selection. If the parent node does not have a lead selection, then the singleton child node is invalid, even though it exists.
Supply function
A supply is needed primarily to populate a singleton node's element collection.
Any context node can have a supply function defined for it.
Check this link for supply function
https://www.sdn.sap.com/irj/scn/go/portal/prtroot/docs/library/uuid/60086bd5-9301-2b10-6f97-a14366a5602b
Thanks,
Tulasi
Edited by: Tulasi Palnati on Jan 28, 2009 12:43 PM