Web programming

Units WEB1P and WEB2P

Struts 2

How Struts 2 is organised

Struts 2 has a different set of components to Struts 1. Its major component pieces are:

Action. An action is the fundamental component that gets executed as a result of an HTTP request. It contains the code that would normally be found in a servlet. Typically you would implement one Action for each request-level function your application performs; each having a unique URL.
Interceptors. Interceptors are applied before and/or after the action has been executed, and allow you to tailor common functionality to your actions. There are a large number of standard interceptors that are designed to do all the most common functions. The configurability of interceptors is also very high.
Results. All actions return a result, which is then used by the framework to determine what to do next. Usually the result of an action is a simple string that is used to identify one of a typically small number of alternative paths to follow when the action is completed.
Packages. Packages are the unit of configuration in Struts 2. This provides a very flexible mechanism because packages can inherit the configuration of other packages.
struts.xml. A Struts 2 web application may have several struts.xml configuration files. This makes configuration more flexible too.
Annotations. Java 5 annotations can be used in place of XML configuration in some cases. This allows better co-ordination between source code and configuration.
Struts 2 tag libraries. These are more flexible and powerful than Struts 1's.
Plug-ins. Struts 2 supports a plug-in architecture that allows further specialisation and optionality.

Struts 2 actions don't require a separate ActionForm class in order to pass request parameters to them. Instead, properties of the action class are used for that purpose. Interceptors can be configured to populate these automatically.

The web browser requests a resource (/mypage.action, /reports/myreport.pdf, et cetera)
The Filter Dispatcher looks at the request and determines the appropriate Action
The Interceptors automatically apply common functionality to the request, like workflow, validation, and file upload handling
The Action method executes, usually storing and/or retrieving information from a database
The Result renders the output to the browser, be it HTML, images, PDF, or something else

Struts 2 architecture (from here)

Examples

Struts2HelloWorld webapp based on the Struts 2 tutorial

Reading

	Last updated by Prof Jim Briggs of the School of Computing at the University of Portsmouth
	The web programming units include some material that was formerly part of the WPRMP, WECPP, WPSSM and WEMAM units.