However new the technologies, we developers have to resolve the same old problems to keep our users and customers happy. Granted, some new challenges make our lives more interesting. However, the same basic issues have to be resolved in order to provide decent systems.
What do users expect from a good information system? Well, as the name suggests, such system should provide a very efficient and flexible access to information. Different users will focus on distinct areas of the database and follow diverse paths to navigate to the same information.
In this article we focus on navigation. We show how to use the PL/SQL Package List preference to give you a free hand to include navigation buttons that call other web server modules and pass parameters containing context information.
To help the reader
we move step by step through the process to provide such navigation to
users. Process steps are illustrated with snapshots of the web modules,
In one module we enable users to view, create, update and delete positions. In another module we provide the same functionality for business units. Our objective is to get Designer to generate code to display a button on the web page that handles positions. When the user clicks on this button the system must display the web page that manages business unit information and automatically bring up the record of the business unit corresponding to the position that the user was looking at.
Now, how do we figure out how to call this module with parameters and make it display one or several specific records?
Listing A outlines
the structure of the called module. We will need to call one of its program
units when users click on our navigation button. Can you guess which one
With this structure in mind, the next step is easy. Designer has already coded a parameterized procedure that queries the database and displays the business unit details. This procedure is ActionQuery. In Listing B we show the header of this procedure in the called module package.
This is the procedure that is called in the business unit module when the user submits the query HTML form by pressing the Find button. So all we have to do is get Designer to generate such an HTML form in the calling module.
We set the web generator preference Text Handling à PL/SQL Package List = wfs_weblib. Wfs_weblib is the package where we put all the custom client code that we need the generator to include. This package must be created on the database server.
Then in the Design
Editor, we navigate to the calling module: pos_mw and double click on its
module component pos_m. A dialog pops up on the screen. The dialog title
is "Edit Module Component <module component name>". If you do not get
this dialog but see the property palette instead, select menu option: Optionsà
Use Property Dialogs and double-click on the module component again. In
the User Text tab we select "Bottom of the View Form" and type this in
the User text: "wfs_weblib.pos_m_but_bu". Note1: do not include the quotes.
Note2: no semi-column is required. The attentive reader will recognize
the package name that we introduced earlier. The function code of pos_m_but_bu
is in Listing C.
If you have analyzed
thoroughly the code in Listing C, you know what server procedure gets called
when the user presses the button: wfs_weblib.call_bu_m. Creating this procedure
is the last step of this technique. If you are not an HTML expert, you
may be surprised that you did not see an explicit call to this procedure
in the onClick trigger of the button. This is what an HTML form does. It
contains a number of items, some text fields, some hidden fields and some
submit items. Our button is a submit item. When users select submit items,
the instructions in the "action" property of the HTML form are executed.
This is how wfs_weblib.call_bu_m is executed.
Important Note: our package wfs_weblib is not as small as listing D suggests. We only show extracts of it for the sake of brevity. For this reason we did not repeat the code shown in Listing C into Listing D, although it is the same package.
In our situation, when in Figure D the user presses on the button "Show PC Detail" the information illustrated in Figure C is displayed. Note that there is only one record in the record list in the left frame in Figure C. This record corresponds to the PC Code assigned to the employee in Figure D.
Giving users an easy access to information is what information systems are all about.
Hervé Deschamps is a Senior Principal Consultant with Oracle Corporation. He has had over five years of experience with Oracle Development Environments (Designer, Developer 2000 and their previous versions). He specialises in tending towards 100% Generation using Designer for both web and client server applications. You can reach him by e-mail at email@example.com. He also maintains a web page full of articles, scripts, tips, techniques at: http://www.iherve.com.