Java Technologies to Use in Web Applications

There are too many Java technologies to list in one article, so this article will describe only the ones most frequently used. The number of technologies listed here can appear overwhelming. Keep in mind that you will not need to use them all. In fact, a web application often consists of nothing more than one page created with the JavaServer Pages (JSP) technology. Sometimes you will combine three or more such technologies. No matter how many you end up using, it's good to know what is available to you and how you can use each one in a web application.

Java Servlet API

The Java Servlet API lets you define HTTP-specific classes. A servlet class extends the capabilities of servers that host applications that are accessed by way of a request-response programming model. Although servlets can respond to any type of request, they are commonly used to extend the applications hosted by web servers. For instance, you might use a servlet to get the text input from an online form and print it back to the screen in an HTML page and format, or you might use a different servlet to write the data to a file or database instead. A servlet runs on the server side -- without an application GUI or HTML user interface (UI) of its own. Java Servlet extensions make many web applications possible.

Figure 1 shows clients talking to Java Servlet extensions. Clients may range in complexity from simple HTML forms to sophisticated Java technology-based applets.



The javax.servlet and javax.servlet.http packages provide the classes and interfaces to define servlets. HTML servlet classes extend the javax.servlet.http.HttpServlet abstract class, which provides a framework for handling HTTP protocol.

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