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Model 1 had a downside: too much code mixed with medication phentermine prescription, so the custom tag invention starts to shine. The custom tag technique opens the door to two new protagonists, XML based programming and expression languages (EL). XML + EL are the "weak" replacement of the typical strong full featured and verbose programming language used before to manage the dynamic parts of the medication phentermine prescription, reducing (slightly) the impedance of both worlds and promoting an improved separation of business code and view. They brought a need to bridge page templates and business code... the "bindings." The next step: why does the view decide the navigation, the target view? The answer to this question is the adaptation of the MVC pattern to the web. In Java the most popular MVC framework, Struts, defines the navigation rules using again XML, in this case the "XML metaprogramming" is not to develop the view, is the MVC glue. Model 2 was born. The Birth of the Event Based Web Model 2 introduced desktop culture in the web. The temptation is near, and the temptation is called "components". HTML form components are very basic and the HTML/W3C world is very conservative to welcome something new. But we need new desktop like drag and drop components beyond form controls...now! The answer is HTML and JavaScript generated by tools. How to package? How to bind with the business code? The Java answer is JSF with more custom tags, more XML files, metaprogramming and Java bindings, and a "new kid on the block" in the server centric world, JavaScript. The server generates and sends to the client custom JavaScript, usually with support of client JavaScript libraries, as the way to add desktop like behavior to the components and to drive user events to the server reloading the page with the new visual state of the component when necessary. The event based web was born. Now AJAX is here, what can we do? Umm... we can generate more custom JavaScript or XML, transporting the data from the server and render this data in the client using JavaScript centric components, or we can build the component view in the server and generate the necessary custom JavaScript from the server to change the appearance of the component in the client as response of user actions. So what is wrong with this path? 1) Custom tags (with custom HTML and JavaScript generation): violates web development culture In the desktop a program's appearance can be fully customized because the developer usually has a pixel based level. You can build your custom controls from scratch but it is usually a hard task. The web space is very different, there is not so much power (for instance there is no API to draw on) but is not difficult to customize the visual appearance of your web application using tags, CSS, and JavaScript. For instance, almost all Swing applications use the default "boring" controls, in web applications every is different and there is no steep learning curve. Traditionally when a web developer fills a with data the developer usually has full control of the layout. This full control is being lost with so many intrusive custom tag based tools. These custom tags usually "replace" the web designer, generating tons of obscure medication phentermine prescription mixed with JavaScript. There are two problems: corporate style may be not fulfilled and complex components are not possible. With simple components this approach may be valid because the CSS has some control of the visual appearance, but with complex components like composite components you are in trouble. 2) XML based metaprogramming: disturbs the Object Oriented Programming paradigm XML is very nice for custom configuration but it is verbose and very poor when used as a pseudo imperative language. The current tendency to use declarative programming underuses the power of OOP because this XML based declarative programming is usually being used in an architectural manner (with a deep architectural impact). For instance, is very hard in XML to declare a feature applying to different levels (globally, locally) or to groups ("batch" configuration). Most of the time you need to repeat the same again and again because the XML format used impose it. Custom tags and XML centric frameworks are usually designed with tools in mind. Tools increase productivity of course, but the most productive tool is reuse, and OOP strongly promotes reusing easily, with XML based components it is very hard to reuse your own work because you need to build your own XML based components otherwise you will be repeating the same again and again. 3) Old tools do not fit with AJAX Most of the server based web frameworks were designed before the AJAX explosion. Many page based frameworks are not very useful in the AJAX space, because a web application with 100 pages can be replaced with a new one with only 1 page, classical navigation utilities are underused with AJAX. This applies to the pre AJAX component (or event) based frameworks too; these frameworks tried to simulate a desktop application using classical navigation with full page reload, the sophisticated techniques used to keep track of the component state while the user navigates, including back and forward button support, are now over engineering. Is there some other alternative? Yes. The design problem of classical web application development is mainly in the view. The view is defined as plain text, this text is never exposed as a DOM tree to the developer, so any binding to business code, declarations, region marks etc are always done in the medication phentermine prescription with special tags, regular expressions etc. Because the normal HTML is treated as plain text only the special tags and regular expressions are the live elements of the page. Components are usually defined with custom tags because it is extremely difficult to delegate the medication phentermine prescription design to the developer because the developer needs to explain to the framework how the medication phentermine prescription design fits in the expected component behavior defined by the framework. The alternative is to repeat the nature of the client in the server, use again the old DOM in the server too, we are in the twenty first century and in the AJAX era where there is no need to rebuild complete pages by any user click. Many years ago this approach had many problems, but these problems are gone; furthermore the problem of the expensive memory use of the DOM can be surpassed using serialization as plain text of the "static subtrees." ItsNat Simulates a Java W3C Browser in the Server I am the author of ItsNat, an open source Java AJAX Component based web application development framework. ItsNat uses the approach described above. This approach is radically new but uses the old tools: the client DOM tree is repeated in the server as a Java W3C DOM tree, exactly the opposite, the client DOM is a clone of the server DOM, if the server DOM changes the client DOM is updated automatically by the framework usually as response of user action, this user action is received as a Java W3C DOM Event transported by AJAX. In short, ItsNat simulates a Java W3C browser in the server. With this approach the starting page may be defined as a pure HTML template, and exposed to the developer as a DOM tree. With a DOM tree the developer has absolute control of the layout including minor changes as the response of an AJAX event. If an AJAX event requires a big change of the page a pure HTML fragment can be loaded converted to DOM and inserted in the document. How to build components? Following the Wicket approach but with the DOM side, defining patterns and telling the framework what is the parent element of a list, table, tree etc what is the pattern of a list item, row, cell, tree node... what is the component structure, in short, attaching the developer defined view to the component. Then component will clone the pattern to create new list items, rows, cells and tree nodes. Conclusion: returning to its roots may be the path to the future in web development. Published Nov. 27, 2007 — Reads 3,889 Copyright © 2007 SYS CON Media. All Rights Reserved. ... medication phentermine prescription