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Server-side dynamic elements produce HTML at runtime. This HTML is composed of the same HTML elements you use when you're creating a static web page. Like static elements, dynamic elements display formatted text, images, forms, hyperlinks, and active images. WebObjects provides several dynamic elements. For a complete list, see the online book Dynamic Elements Reference.

For an example of dynamic elements in action, look at the CyberWind sample application. It's located in <DocRoot>/WebObjects/Examples/Java/CyberWindJava, where <DocRoot> is your web server's document root. When you run CyberWind, its first page contains a list of hyperlinks, shown in Figure 9.

This list is not hard-coded into the page. Instead, it is produced by several dynamic elements. Figure 10 shows how this same part of the page looks in WebObjects Builder.

The elements shown in Figure 10 are a WORepetition, a WOHyperlink, and a WOString. The WORepetition element corresponds to a for loop in C code. That is, it iterates through a list of items and, for each item in that list, prints its contents. In this example, the contents are a WOHyperlink and a WOString. The WOHyperlink is a hyperlink whose destination is determined at runtime, and the WOString is a string whose contents are determined at runtime.

When you run CyberWind, the WORepetition walks through an array of strings that the component's code supplies. For each item in the array, it displays a hyperlink whose text is the text of the string item in the array. In this array, there are two strings-"See surfshop information" and "Buy a new sailboard"-so the WORepetition creates two hyperlinks, each containing the appropriate text.

As the name implies, server-side dynamic elements operate entirely on the server (see Figure 11). That is, when a server-side dynamic element is asked to draw itself, it returns HTML code that should form part of a page, the page is constructed, and then the entire page is sent from the server to the client. Later in this chapter, you'll learn about client-side components, which transport values and state from the server to the client and then draw themselves on the client machine.

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