JSPs, like Servlets, are concerned with dynamically generated web content. These two web components—Servlets and JSPs—comprise a huge percentage of the content of real-world Java EE applications.
Building Servlets involves building Java components that emit HTML. In a lot of cases, that works out well. However, that approach isn’t very accessible for people who spend their time on the visual side of building web applications and don’t necessarily care to know much about software development. Enter JSP. JSP pages are HTML-based text documents with chunks of Java code called scriptlets embedded into the HTML document.
When JSPs are deployed, something remarkable happens: The contents of the JSP are rolled inside out, like a sock, and a Servlet is created based on the embedded tags and Java code scriptlets, as shown in next Figure. This happens pretty much invisibly. If you care to, you can dig under the covers and see how it works (which makes learning about Servlets all the more worthwhile).
Building Servlets involves building Java components that emit HTML. In a lot of cases, that works out well. However, that approach isn’t very accessible for people who spend their time on the visual side of building web applications and don’t necessarily care to know much about software development. Enter JSP. JSP pages are HTML-based text documents with chunks of Java code called scriptlets embedded into the HTML document.
When JSPs are deployed, something remarkable happens: The contents of the JSP are rolled inside out, like a sock, and a Servlet is created based on the embedded tags and Java code scriptlets, as shown in next Figure. This happens pretty much invisibly. If you care to, you can dig under the covers and see how it works (which makes learning about Servlets all the more worthwhile).
You may have had some exposure to JavaScript, which is a Java-like scripting language that can be included within a web page, and is executed by the web browser when a page containing JavaScript code is sent to the browser. JSP is a little like that, but the code is compiled and executed at the server, and the resulting HTML is fed back to the requesting client. JSP pages are lightweight and fast (after the initial compilation to the Servlet), and they provide a lot of scalability for web-based applications.
Developers can create both static and dynamic content in a JSP page. Because content based on HTML, XML, and so on forms the basis of a JSP page, a nontechnical person can create and update that portion of a page. A more technical Java developer can create the snippets of Java code that will interface with data sources, perform calculations, and so on—the dynamic stuff.
ince an executing JSP is a Servlet, JSP provides the same support for session management as Servlets. JSPs can also load and call methods of JavaBean components, access server-based data sources, or perform complex calculations at the server.
Developers can create both static and dynamic content in a JSP page. Because content based on HTML, XML, and so on forms the basis of a JSP page, a nontechnical person can create and update that portion of a page. A more technical Java developer can create the snippets of Java code that will interface with data sources, perform calculations, and so on—the dynamic stuff.
ince an executing JSP is a Servlet, JSP provides the same support for session management as Servlets. JSPs can also load and call methods of JavaBean components, access server-based data sources, or perform complex calculations at the server.
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