The Servlet API is the foundation of almost all Java Web View technologies. Servlet provides the basic mechanism for writing Java classes for web applications. Servlets can respond to HTTP requests, create cookies and maintain sessions.
Built on top of the Servlet API, JSP provides a document-centric, tag-based templates, server programming model which can generate many forms of textual content.
Java code may be embedded in JSP files and is compiled and executed when a request is received.
Struts provides for a decoupling of the Controller and the View.
Requests are received by a Java Class (Controller) which can decide which View to display.
The actual View can be written in different view technologies, like JSP, free marker template, velocity template etc.
An XML configuration file is used to specify the "Page Navigation", i.e. the flow of the request to the appropriate Controller, and which View to display based on the outcome of the Controller.
Pages directly interact with stateful Java components on the server.
Components and their state are managed by the Wicket framework, freeing the application developer from having to use HttpSession directly to manage state.
Does not require XML for configuration.
Compared to JSPs, enforces a clear separation of HTML markup and Java code.
Web page components are 'pushed' into the HTML markup from the code.
Typically uses Facelets for XML/XHTML-based templating.
Classes are written as POJOs, with Annotations or XML configuration files used to associate them with page and component templates.
The Unified Expression Language allows binding component fields and events to POJO bean properties and methods.
Conversion and validation constraints can be specified in Facelets and are automatically applied, normally resulting in reposting of the same page with error information in case of failure.
Navigation can be via configuration file rules or directly specified in the page.
SiteMesh is an HTML templating framework based on the "Decoration" model.
It allows for the creation of a 'decoration' template which is then applied to any other HTML to generate a new HTML.
The newly generated HTML contains elements from the original HTML blended into the template.
This allows for the original HTML to be very simple and devoid of any formatting or layout specification. The template, in turn, is devoid of any actual information.
