A real case which is related to Automatic Delta Handling
I use a ticket which I am struggling with recently to start this blog. It took me almost the whole day to dig out the root cause.
How to reproduce the issue – Just create a new Product by clicking new Product button:
How I find the root cause
Since the UI page didn’t crash, there is no surprise that I didn’t find any related dumps in ST22.
I am 100% sure that there must be some exception occurred in the backend and caught by framework, but unfortunately without any message raised out in UI. So I use the tip described in my blog to start debugging. Several minutes later, I felt really frustrated since the breakpoint for ABAP keyword CATCH is triggered so frequently in UI framework processing. I was completely lost in the debugging. ( At that time I didn’t try conditional breakpoint group since I am not sure whether it could help)
Then I asked for help from one colleague who is an UI expert. He suggested:” Hey, try to switch off delta handling and try again”. Wait, what is the delta handling? After exploring for quite a time I switched it off and retry, here below is the result under delta handling off mode:
Here below is something more I want to share with you regarding Automatic delta handling
What is Delta Handling mechanism in Webclient UI?
The Delta Handling is a collection of mechanisms to reduce the rendering time on the client and the network load when transporting the request and response between server and client. It consists of Manual delta handling ( out of scope of this blog) and Automatic delta handling. The Manual Delta Handling bases on the tag library TAJAX. With this library we can define areas on views and rules for updating these areas basing on events.
In most of the case Automatic Delta Handling (ADT) is used. The ADH uses also the technique provided by the tag library TAJAX. Instead of defining complex rules for dependencies between TAJAX-areas, when the page is being prepared for the rendering, ADH detects which areas (e.g. views) of the page have changed. Only such changed areas are then redrawn in the browser. It is nearly transparent for we application developer, as long as there is no too complicated JavaScript used in the UI page. If you are interested with this, you could read the comment on method CL_AJAX_UTILITY->SHOULD_RENDER and debug it.
