This week I came across a hard to find error using task flows, which was caused by a simple reason.
I tired out Frank Nimphius samples #52 about using task flows which are not part of the application itself, but which are added from adf libraries to the application. First I tried the sample Frank provided in the Code Corner article, which worked as expected after changing the db connections to my environment.
Next I’d build my own task flow in an adf library and tired to use it in the parent application as reagion. All went OK till I run the application. Here is the picture
As you can see the region representing the task flow from the library is not shown or empty. The first step to analyze the error was to inspect the task flow in the library which looked like:
This looked OK for me and a further visual inspection of each of the other elements did not show any difference compared to Franks sample. Here are the images of the method call activity
and the navigation together with the navigation target
After some more checking I saw the hint which finally lead me to finding the error. In the image above you see a yellow or brownish frame around the ‘From Outcome’ field. I didn’t pay much attention to this at first, but after checking the ‘setdeptId’ method call outcome and the navigation targets ‘From Outcome’ I saw the difference.
The ‘setdeptId’ method call had ‘setdeptId’ set as ‘Fixed Outcome’ whereas the navigation was set to ‘goEmployees’. Once these two attributes are set to the same value the the color frame is gone.
Some questions still to answer:
(q1) Why don’t you get any error output in the log when running the application?
(q2) Why do you see no other error or warning in the design view in JDeveloper?
The answer to (q1) is easy once you found the reason for the error. As the method call activity (setting the department id and executing the query) did not throw an error, the navigation took place. As the outcome was set to not existing target, the region remains empty. A this could be desired behavior and no exception occurred no log output is generated.
Question (q2) took some more research. Lately I wrote a couple of blog entries with many pictures from the samples I used to show something. Some of of the images I used showed a small yellow attention sign when e.g. a page element on a task flow when the page is not created jet. As I took some of the images before the pages where ready and I didn’t want to show the warnings in my pictures, I turn the warnings off. This is not a problem as I later created the missing pages. But I forgot about this change with the result that the visual warning for the error I described here was hidden.
With the warning turned on again the error is easy to detect:
To turn the ‘Show Warning’ on or off you drop down the ‘Show’ list box in the diagram view of a task flow or page:
So, always remember to reset settings you only change for your convenience or make sure you never forget their impact.