Understanding APEX URL synax

A good understanding of the way APEX uses URL’s helps you to easily navigate through your applications. It’s also helpful for version control and maintenance. In this post I will highlight the key features of the APEX URL syntax, complete documentation on the URL syntax can befound here

The URL consists of a static part for the domain and DAD, and a dynamic part, consisting of an number of colon delimited parameters. A typical APEX URL looks like: http://apex.oracle.com/pls/apex/f?p=42742:8:100133297155888::NO::P8_ROWID:ABSCZ%2FAE7AAAACVAAD This URL encloses information for navigation (to the coorect page) as well as identification and a bunch of other info as well. To break it down the URL consists of the following parts:

• http://apex.oracle.com - the domain/URL of the server
• pls - refers to the mod_plsql cartridge being used by the weblistener
• apex - is the database access descriptor (DAD). This is used by the HTTP server to connect to the database server
• f?p= - This is just a prefix used by APEX
• 42742 – the ID of the application being called
• 8 – the ID of the page being called
• 100133297155888 – the ID of the current session
• NO - Debug mode is set to ‘NO’
• P8_ROWID - a page item ROWID on page 8
• ABSCZ%2FAE7AAAACVAAD - the value to which P8_ROWID will be set

To link between pages in your application you can use an URL to has the following parameters

The following table describes all the parameters in the URL:

Syntax	Description
App	The application ID or the application alias
Page	The page ID or the page alias
Session	Identifies a session ID. You can reference a session ID to create hypertext links to other pages that maintain the same session state by passing the session number. You can reference the session ID using the syntax: Short substitution string: &SESSION. PL/SQL: V('SESSION') Bind variable: :APP_SESSION
Request	Sets the value of REQUEST. Each application button sets the value of REQUEST to the name of the button which enables accept processing to reference the name of the button when a user clicks it. You can reference REQUEST using the syntax: Substitution string: &REQUEST. PL/SQL: V('REQUEST') Bind variable: :REQUEST
Debug	Displays application processing details. Valid values for the DEBUG flag include: YES. LEVELn NO Setting this flag to YES displays details about application processing. Setting this flag to LEVELn (where n is between 1 and 9) controls the level of debug detail that displays. The value of YES equals LEVEL4. You can reference the Debug flag using the following syntax: Short substitution string: &DEBUG. PL/SQL: V('DEBUG') Bind variable: :DEBUG
ClearCache	Clears the cache. This sets the value of items to null. To clear cached items on a single page, specify the numeric page number. To clear cached items on multiple pages, use a comma-separated list of page numbers. Clearing a page's cache also resets any stateful processes on the page. Individual or comma-separated values can also include collection names to be reset or the keyword RP, which resets region pagination on the requested page. The keyword APP clears cache for all pages and all application-level items in the current application and removes sort preferences for the current user. The keyword SESSION achieves the same result as the APP keyword, but clears items associated with all applications that have been used in the current session.
ItemNames	Comma-delimited list of item names used to set session state with a URL.
ItemValues	List of item values used to set session state within a URL. Item values cannot include colons, but can contain commas if enclosed with backslashes. To pass a comma in an item value, enclose the characters with backslashes. For example: \123,45\
PrinterFriendly	Determines if the page is being rendered in printer friendly mode. If PrinterFriendly is set to Yes, then the page is rendered in printer friendly mode. The value of PrinterFriendly can be used in rendering conditions to remove elements such as regions from the page to optimize printed output. You can reference the printer friendly preference by using the following syntax: V('PRINTER_FRIENDLY') When referenced, the Application Express engine does not display tabs or navigation bars, and all items are displayed as text and not as form elements.

The application- and page aliases, as well as the substitution strings for session, request and debug, are very handy for linking between pages, say when you want to use a button to redirect to another page in your application. They play a role in maintenance too.

The session ID is unique for each session, so if you put your session hardcoded in the redirecting URL, navigation will only work for your current session, the URL will be useless as soon as your session has expired. Using application and page aliases are helpful for example when you want to move your application from development to production. The application ID you used in the development environment might not be available in your production environment . So if all redirecting URL’s in your application have the application ID hardcoded, redirection will no longer work. Using an application alias solves this problem. The page alias is mostly helpful for creating understandable navigation. You can let your users navigate to a page called ‘home’, instead of page ‘1’.

To make your page even more independent of hardcoded values, you can consider replacing the ‘P_’ part of your page items by ‘_’ .doing so enables you to move your page within your application without losing navigation logic.