SiteMesh3 Overview

SiteMesh is a web-page layout and decoration framework
SiteMesh intercepts requests to any static or dynamically generated HTML page requested through the web-server, processes the content and then merges it with one or more decorators to build the final result.
Sitemesh removes your burden of including layout related files in each and every page of your application.

Lets take a look at what sitemesh does

Normally websites have a common layout for all the pages. There is a header, navigation on top or left or right and a footer. Generally in such a site, we use jsp:include on every page to include the header, navigation and footer. This creates maintenance problems.
By using Sitemesh, we don’t need to include the header, navigation and footer into each and every page. We create only the content of the page, Sitemesh adds the header, navigation etc to the page.

Work flow:

SiteMesh in web applications

In a web application, SiteMesh acts as a Servler Filter.
It allows requests to be handled by the Servlet engine as normal, but the resulting HTML (referred to as the content) will be intercepted before being returned to the browser.
The intercepted content has certain properties extracted (typically the contents of the <title>, <head> and <body> tags and is then passed on to a second request that should return the common look and feel for the site (referred to as the decorator).
The decorator contains placeholders for where the properties extracted from the content should be inserted.
a key component of the SiteMesh architecture is the content processor. This is an efficient engine for transforming and extracting content from HTML content.
As with most sites, there is a header, a navigation at the top, a navigation on the left, the content goes on the right and there is a footer at the bottom.
If we use sitemesh, we’ll create a template page which will have the layout related to the site. That template will be applied to every page of the site.

Create a page that will contain the header, navigations and footer etc

SiteMesh uses a filter to intercept every request that is received by the application which we might want Sitemesh to process.
Sitemesh uses a configuration document (decorators.xml) to see which layout or template (called decorator) to apply to the request (if required).