Java Data Objects

Web Servers

In order to describe where JDO fits into a web server, we start with a brief overview of the web container and how the container handles requests. The application components that handle the requests can use JDO to provide access to persistent information used to service the requests.

There is no standard for all the characteristics of web servers and the services they support, but most implementations support applications written to implement HTTP and HTTPS messages. Since the details of security and secure access to these services are not important to the implementation using JDO, we will use HTTP to describe both HTTP and HTTPS protocols. The use of HTTPS is transparent to the application.

HTTP is a request/response protocol in which a browser sends a request to a server at a specific Internet address and waits for a response from the server. The server parses the request and delegates its handling to the responsible component, based on policy files used to configure the server.

HTTP responses can be static (i.e., their content never changes). Graphics, web-page templates, banners, and other artifacts of web pages are primarily static, and web servers typically cache these items and deliver them to users on request.

Other HTTP responses are dynamic . The response is generated only upon receipt of the request and may depend on current information (time of day, current price of a stock, etc.) or the requester (contents of a shopper’s cart, value of a portfolio, etc.). These ...