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Oracle Web Applications: PL/SQL Developer's Intro by Andrew Odewahn

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Content Delivery Model

In this section I’ll explain how the OAS and WebDB servers apply the ideas introduced in the previous section to deliver content from the server to the client (e.g., URLs, virtual directories, ports, etc.).

Although the specific details vary, OAS and WebDB follow the same basic process model to deliver web content and rely on a virtual schema mapping called a Database Access Descriptor (DAD) to access the database. A DAD is similar to a virtual directory mapping; it creates a name, used within a URL, that links the request to a specific schema in the database.

Figure 2.1 illustrates the basic parts of the model.

Basic components of OAS and WebDB systems

Figure 2-1. Basic components of OAS and WebDB systems

A request begins when a user submits a URL or an HTML form to an OAS or WebDB server. A server component called the HTTP listener intercepts the request and extracts its path section. This step, called URL resolution, determines what type of resource the request is for and how it will be processed. If the URL’s path section matches a virtual directory mapping, then the request is for a static resource and the HTTP listener returns the requested resource (if found) to the user’s browser. If the path section matches a DAD stored in the server’s configuration files, the request is for a dynamic resource and the HTTP listener forwards, or dispatches, the request to the PL/SQL gateway.

The PL/SQL gateway ...

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