Welcome to Apache Struts 2
Apache Struts 2 is a flexible control layer based on standard technologies like Java Filters, JavaBeans, ResourceBundles, Locales, and XML, as well as various OpenSymphony packages, like OGNL and XWork. The framework helps you create an extensible development environment for your application, based on industry standards and proven design patterns.
Work in progress!
Apache Struts 2 is at a pre-release, pre-Alpha stage. If you are just getting started with Struts2/WebWork2, we recommend WebWork 2.2 as an entry point. WW2 is stable and production ready. When Struts 2 is released, migration paths for WebWork 2 and Struts 1 developers will be available.
See the Struts 2 release plan for details and status.
Apache Struts 2 in a Nutshell
The framework provides its own web Controller component and integrates with other technologies to provide the Model and the View. For the Model, the framework can interact with standard data access technologies, like JDBC and EJB, as well as most any third-party packages, like Cayenne, Hibernate, or iBATIS. For the View, the framework works well with JavaServer Pages, including JSTL and JSF, as well as FreeMarker or Velocity Templates, PDF, XSLT, and other presentation systems.
The framework's Controller acts as a bridge between the application's Model and the web View. When a request is received, the Controller invokes an Action class. The Action class consults with the Model (or, preferably, a Facade representing your Model) to examine or update the application's state. To transfer data between the Model and the View, properties can be placed on the Action class, or on a plain old JavaBean.
Most often, the Model is represented as a graph of JavaBean objects. Preferably, the Model will do the "heavy lifting", and the Action will act as a "traffic cop" or adapter. The framework provides sophisticated, automatic type conversion to simplify transfering data between rich domain objects and text-only HTTP requests.
To make it easier to access dynamic data obtained by an Action, the framework includes a library of custom tags. The tags interact with the framework's validation and internationalization features, to ensure that input is correct and output is localized. The tag library can be used with JSP, FreeMarker, or Velocity.
Struts Configuration in a Nutshell
A web application uses a deployment descriptor to initialize resources like servlets and taglibs. The deployment descriptor is formatted as a XML document and named
web.xml. Likewise, the framework uses a configuration file, named
struts.xml, to initialize its own resources. These resources include action mappings, to direct input to server-side Action classes, and result types, to select output pages.
Here's a simple configuration (
struts.xml) for a login workflow:
Aside from actions and results, you can also specify exception handlers and interceptors. Interceptors specify the "request-processing lifecycle" for an action. (What happens to the request before and after the Action class fires.) You can specify both global and local lifecycles. If some of your actions respond to AJAX, SOAP, or JSF requests, you can simplify the lifecycle, and even just "pass through" the request, if you like.
Struts 2 is extensible. Very extensible. Every class deployed by the framework is based on an interface. We provide base classes, but you can substitute your own. In the case of Action classes, even the interface is optional. POJO web development is here!
The framework provides general-purpose defaults, so you can start using Struts 2 "out of the box" right away. As needed, you can override any of our defaults in your application's configuration. We provide the base framework, but you can still write your application your way.
The documentation is grouped into three areas.
Our tutorials are designed to get started with the framework soon as possible. We offer an all-purpose "soup to nuts" tutorial as well as specialty tutorials on portlets and database access.
Our FAQs provide a wide range of rapid-fire "HOWTOs" in question and answer format.
Our in-depth guides focus on specific components of the framework, such as Views, the Core framework, and Third-party Extensions.
An overview of all three areas is available.