Page History

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Feature \| SAF 1 \| SAF 2
*Action classes* \| SAF 1 requires Action classes to extend an Abstract base class. A common problem in SAF 1 is programming to abstract classes instead of interfaces. \| An SAF 2 Action may optionally implement the {{com.opensymphony.xwork.Action}} Interface, with a series of other Interfaces for other services. SAF 2 provides a base ActionSupport class to implement these Interfaces.
*Threading Model* \| SAF 1 Actions must be thread-safe because there will only be one instance to handle all requests. This strategy places restrictions on what can be done with SAF 1 Actions as any resources held must be thread-safe or access to them must be synchronized. \| SAF 2 Actions are instantiated for each request, so there are no thread-safety issues. In practice, Servlet containers generate many throw-away objects per request, and one more Object does not prove to be a problem for performance or garbage collection.
*Servlet Dependency* \| SAF 1 Actions have dependencies on Servlets because they pass the  HttpServletRequest and HttpServletResponse to an Action. \| SAF 1 Actions are not tied to a container. Most often the Servlet contexts are represented as simple Maps, allowing the Action to be tested in isolation. If necessary, SAF 2 Actions can still directly access to the request and response.
*Testability* \| A major hurdle to testing SAF 1 Actions is that the {{execute}} method exposes the Servlet API. A third-party extension, Struts TestCase, offers a set of mock object for SAF 1. \| SAF 2 Actions can be tested by instantiating the Action, setting properties, and invoking methods. Dependency Injection support can make testing even simpler
*FormBeans* \| SAF 1 uses an ActionForm object to capture input, which can create a lot of extra classes. DynaBeans are often used as an alternative to creating conventional ActionForm classes. \| SAF 2 allows you to have all of your properties directly accessible on your Action as regular Javabeans properties, including rich Object types which can have their own properties which can be accessed from the web page. SAF 2 does supports the ActionForm pattern, along with ModelDriven Actions, which allow you to have a rich Object type or domain object as your form bean, with its properties directly accessible to the web page, rather than accessing them as sub-properties of a property of the Action.
*Expression Language* \| SAF 1 integrates with JSTL, so it uses the JSTL EL. The EL has basic object graph traversal, but relatively weak collection and indexed property support. \| SAF 2 uses OGNL which is a powerful and flexible expression language SAF 2 can also use JSTL
*Binding values into views* \| SAF 1 uses the standard JSP mechanism for binding objects into the page context for access. \| SAF 2 sets up a ValueStack which the taglibs access to dynamically find values without tightly coupling your view to the types it is rendering. This strategy allows reuse of views across a range of types which have the same properties.
*Type Conversion* \| SAF 1 ActionForm properties are usually all Strings. SAF 1 uses Commons-Beanutils for type conversion. Converters are per-class, and not configurable per instance. \| SAF 2 uses OGNL for type conversion with added converters provided for all basic types.
*Validation* \| SAF 1 supports manual validation via a {{validate}} method on the ActionForm, or through an extension to the Commons Validator. Classes can have different validation contexts for the same class, but cannot chain to validations on sub-objects. \| SAF 2 supports manual validation via the {{validate}} method and the XWork [Validation] framework. The Xwork Validation Framework supports chaining validation into sub-properties using the validations defined for the properties class type and the validation context.
*Control Of Action Execution* \| SAF 1 supports separate Request Processors (lifecycles) for each module, but all the Actions in the module share he same lifecycle. \| SAF 2 supports creating different lifecycles on a per Action basis via Interceptor Stacks.
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