Context Change Log (Recording User Entries)

Use

In many applications, it is important that user entries are actually marked as user entries. If, for example, many bound UI elements are displayed in a view, but only one single value is changed by a user entry, this can have an unnecessary negative effect on performance when all the context contents are again processed by the business logic. It is more appropriate to mark the changes that the user has made within the view and to edit them separately. Changes that the user can make include changing the value of an attribute and converting the selection or the lead selection.

First of all, each context node provides the option of storing the relevant information for itself. However, to prevent you having to check all existing context nodes of a controller, Web Dynpro Framework provides a context change log function: Within a controller all information about changes made to context elements by the user are saved only in an internal table . The Web Dynpro runtime has access to this table and can adapt the flow of business logic to the table entries.

Note

The table records solely changes made by the user; changes to context elements that were made in the programs (for example, dynamic programming) are not listed.

Caution

Note that context changes are recorded only for the original node and not for mapped nodes.

The function of the context change log is switched off in the controller default settings. You may activate it as required. You do this by using the IF_WD_CONTEXT interface of the respective controller.

IF_WD_CONTEXT Interface

The IF_WD_CONTEXT interface provides a reference to the controller context.

Caution

In contrast to the IF_WD_CONTEXT_NODE interface, IF_WD_CONTEXT does not refer only to the root node of the context but to the context as a whole.

Use the following call to get a reference to IF_WD_CONTEXT:

MY_CONTEXT = WD_CONTEXT->GET_CONTEXT( )

The IF_WD_CONTEXT interface makes the following methods available for using the change log function:

Method	Description
ENABLE_CONTEXT_CHANGE_LOG( )	Activates recording of user entries for this controller.
DISABLE_CONTEXT_CHANGE_LOG( )	Deactivates the recording.
GET_CONTEXT_CHANGE_LOG( and_reset )	Provides the current content of the change log table and resets this automatically (the latter property is preset, it can however be deactivated again).
RESET_CONTEXT_CHANGE_LOG( )	Resets the change log table.
ADD_CONTEXT_ATTRIBUTE_CHANGE( )	You can use this method to program changes to a context attribute into the change log table. This is particularly important for programming value helps, since data selected from a value help is not automatically entered in the change log table.

Table of User-Defined Context Changes

The table in which the user-defined changes to context are listed is of the type WDR_CONTEXT_CHANGE_LIST. It contains nine columns which have the following meanings:

Column	Description
NODE_NAME	Name of the node containing the change
SEQUENCE	Sequence number of the entry
NODE	Reference to the node
NODE_PATH	Node path
CHANGE_KIND	Categorizes the type of change. Constants IF_WD_CONTEXT=>CHANGED_* are available as values.
ELEMENT_INDEX	Index of context element
ATTRIBUTE_NAME	Name of the attribute that was changed
OLD_VALUE	Reference to the previous value
NEW_VALUE	Reference to the new value

For the values in the columns OLD_VALUE and NEW_VALUE, a copy is first made of the old and the new attribute values. A reference to this copy is then stored in the table.

Note

Changes in the lead selection are also recorded as changes in the selection.

In the case of OVS value helps and freely programmed value helps , the new value is not entered automatically into the table but must be entered actively using method ADD_CONTEXT_ATTRIBUTE_CHANGE of interface IF_WD_CONTEXT, provided an entry is desired.

Example

You will find an example application DEMO_CONTEXT_CHANGES in your system in package SWDP_DEMO.