The Unbearable Lightness of Java

Decora decora logo

Decora is web decoration framework to help in creating sites consisting of pages based on templates. This gives a consistent look/feel, navigation and layout scheme. Decora intercepts requests, process the content and merges it with decorator to create a final page result.

Decora is based on Lagarto parser and therefore is very, very fast.

Setup

Enable Decora filter in web.xml:

	<filter>
		<filter-name>decora</filter-name>
		<filter-class>jodd.decora.DecoraServletFilter</filter-class>
		<init-param>
			<param-name>decora.manager</param-name>
			<param-value>com.uphea.AppDecoraManager</param-value>
		</init-param>
	</filter>
	<filter-mapping>
		<filter-name>decora</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>

Here we also defines custom DecoraManager instance. DecoraManager is responsible if some request should be decorated and resolves decorator path. By default, DecoraManager decorates all requests, all mime types for all *.html action paths. Default decorator is "/decora/main.jsp".

Decora may be used offline, too. It is not required to use it in web environment.

DecoraManager

DecoraManager does two things: determines what requests should be decorated and resolves decorator path for requests. While determining what requests should be decorated, there are following options:

  • request in general
  • content type, mime type, encoding
  • status code

Resolving decorators path is very simple: for given request and action path DecoraManager must return decorator path (or null if request does not have to be parsed).

Here is an example of DecoraManager that decorates some additional paths:

public class AppDecoraManager extends DecoraManager {

	@Override
	public String resolveDecorator(HttpServletRequest request, String actionPath) {
		if (actionPath.endsWith(".html")) {
			return DEFAULT_DECORATOR;
		}
		if (Wildcard.match(actionPath, "/q/*")) {
			return DEFAULT_DECORATOR;
		}
		return null;
	}
}

 

Decorator

The decorator is a template that contains the common layout and style that should be applied to some set of pages in the web application. In decorator file you can define one or more regions.

Decora regions are defined using decora tags, for example:

<!DOCTYPE html>
<html>
<head>
	<title><decora:title>default title</decora:title></title>
	... more javascript, css, meta etc.
	<decora:head/>
</head>
<body>
<div id="wrapper">
	<decora:body/>
</div>
</body>
</html>

Here we used custom decora tags.

Decora decorators may be static files or dynamic files, created using technologies like JSP, freemarker, etc. Decora tags are simple text tags.

Standard tags for regions

But this is not the only way how to create Decora regions. You can use any standard HTML tag using Decora specific id, for example:

<!DOCTYPE html>
<html>
<head>
	<title><span id="decora-title">default title</span></title>
	... more javascript, css, meta etc.
	<decora:head/>
</head>
<body>
<div id="wrapper">
	<div id="decora-div-main"/>
</div>
</body>
</html>

Decora specific id consist of three parts, separated by a dash: decora prefix, tag name and, optionally, tag id. So

Content regions

Region content is defined in a simple, non-decorated HTML page.

<html>
<head>
	<title>Hello Jodd</title>
	<meta name="description" content="cool jodd page">
</head>
<body>
	<p>Hello <b>Jodd</b>!</p>
</body>
</html>

We defined here 3 regions:

  • title - defined by 'title' tag
  • head - everything between 'head' tags, not including other regions (therefore, excluding the 'title').
  • body - everything between 'body' tags.

Standard tags for regions

When decorator is defined using standard HTML tags, the content may be defined like this:

<html>
<head>
	<title>Hello Jodd</title>
	<meta name="description" content="cool jodd page">
</head>
<body>
	<div id="main">
		Hello <b>Jodd</b>!
	</div>
</body>
</html>

Note that the 'main' region is defined by the div tag with specified id.

Result

The resulting content is decorator page merged with the content by replacing region definitions with its content.

Contents

Documentation

Jodd

Jodd WOT

Examples

Reports

Jodd Library  Jodd Framework