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TCP/IP Tutorial and Technical Overview - IBM Redbooks

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alternative dynamic portion each time the document is sent to the client's<br />

browser. This dynamic portion invokes an appropriate servlet <strong>and</strong> passes to it the<br />

parameters it needs. The replacement is performed at the server <strong>and</strong> it is<br />

completely transparent to the client. Pages that use this technology have the<br />

extension .shtml instead of .html (or .htm).<br />

JavaServer Pages (JSP)<br />

This is an easy-to-use solution for generating HTML (or other markup languages<br />

such as XML) pages with dynamic content. A JSP file contains combinations of<br />

HTML tags, NCSA tags (special tags that were the first method of implementing<br />

server-side includes), tags, <strong>and</strong> JSP syntax. JSP files have the<br />

extension .jsp. One of the many advantages of JSP is that it enables<br />

programmers to effectively separate the HTML coding from the business logic in<br />

Web pages. JSP can be used to access reusable components, such as servlets,<br />

JavaBeans (reusable Java objects), <strong>and</strong> Java-based Web applications. JSP<br />

also supports embedding inline Java code within Web pages. JSPs are typically<br />

compiled into servlets for execution.<br />

Objects<br />

One main thrust in developing content on the Web is the use of objects. In<br />

general, objects allow for decreased application development cost <strong>and</strong> effort by<br />

promoting the reusability of code. In addition, they allow for cooperation <strong>and</strong><br />

coordination between different processes (<strong>and</strong> machines) by enabling operations<br />

that change the state of particular objects. That is, the term object is sometimes<br />

used to describe an implementation of reusable data structures <strong>and</strong> functions,<br />

but can also be used to described the instantiation of those data structures <strong>and</strong><br />

functions.<br />

JavaBeans<br />

According to its inventors at JavaSoft, a JavaBean is a reusable software<br />

component that can be manipulated visually by using a builder tool. The JavaSoft<br />

definition allows for a broad range of components that can be thought of as<br />

beans.<br />

JavaBeans can be visual components, such as buttons or entry fields, or even an<br />

entire spreadsheet application. JavaBeans can also be non-visual components,<br />

encapsulating business tasks or entities, such as processing employee<br />

paychecks, a bank account, or even an entire credit rating component.<br />

Non-visual beans still have a visual representation, such as an icon or name, to<br />

allow visual manipulation. While this visual representation might not appear to<br />

the user of an application, non-visual beans are depicted on screen so that<br />

developers can work with them.<br />

618 <strong>TCP</strong>/<strong>IP</strong> <strong>Tutorial</strong> <strong>and</strong> <strong>Technical</strong> <strong>Overview</strong>

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