Understanding How Authentication Works

You determine how your application interacts with users. If all users have the same rights and privileges they are referred to as public users. However, if your application needs to track each user individually, you need to specify an authentication method.

Authentication establishes the identity of each user who accesses your application. Many authentication processes require a user provide some type of credentials such as a username and password. These credentials are then evaluated and they either pass or fail. If the credentials pass, the user has access to the application. Otherwise, access is denied.

Once a user has been identified, the Application Express engine keeps track of each user by setting the value of the built-in substitution string APP_USER. As a user navigates from page to page, the Application Express engine sets the value of APP_USER to identify the user. The Application Express engine uses APP_USER as one component of a key for tracking each user's session state.

From a programming perspective, you can access APP_USER using the following syntax:

From PL/SQL:
```
V('APP_USER')
```
As a bind variable from either PL/SQL or SQL:
```
:APP_USER
```

You can use APP_USER to perform your own security checks and conditional processing. For example, suppose you created the following table:

CREATE TABLE my_security_table (
  user_id   VARCHAR2(30),
  privilege VARCHAR2(30));

Once created, you could populate this table with user privilege information and then use it to control the display of pages, tabs, navigation bars, buttons, regions, or any other control or component.