Some important Facts in Struts 2.0 Framework
1) Struts controller (DispatcherFilter,ActionServlet) uses the Command Design Pattern,Action classes use Adapter Design Pattern and process() method of the RequestProcessor uses the Template Method Design Pattern.
2) MVC is the main pattern behind struts development. JSPs are used for view and then there is controller (Front controller Pattern) and then there is model.
3) Struts uses ValueObject pattern also as we normally encapsulate all the data in an object and then pass it to JSPs.
Struts also implement the following J2EE design patterns.
* Service to Worker
* Dispatcher View
* Composite View (Struts Tiles)
* Front Controller
* View Helper
* Synchronizer Token
Is it Inversion of Control ???
If yes, how does inversion of control happen in struts 2.0?
I have heard that this concept is used in Spring but not sure if it is in struts.
Struts2 is based on WebWork which has IoC. Struts2 supports interface injection (IOC).
1) In this article we will talk about the new features in Struts 2.0. Over the years, every developers believes that struts is the best and simple framework to implement. Since last two years, more new frameworks come to the market and the use of Struts is declined. Lack of updation in the Struts framework is the main reason for developers choosing alternative framework. To answer this, Struts team comes with the Struts 2.0, an integration of Struts 1.0 with Webwork. Here we will look into the prominent features in the new framework.
Action classes
2) An Struts 2 Action may implement an Action interface, along with other interfaces to enable optional and custom services. Struts 2 provides a base ActionSupport class to implement commonly used interfaces. Albeit, the Action interface is not required. Any POJO object with a execute signature can be used as an Struts 2 Action object.
Threading Model
3) Struts 2 Action objects 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 impose a performance penalty or impact garbage collection.)
Testability
4) Struts 2 Actions can be tested by instantiating the Action, setting properties, and invoking methods. Dependency Injection support also makes testing simpler.
Servlet Dependency
5) Struts 2 Actions are not coupled to a container. Most often the servlet contexts are represented as simple Maps, allowing Actions to be tested in isolation. Struts 2 Actions can still access the original request and response, if required. However, other architectural elements reduce or eliminate the need to access the HttpServetRequest or HttpServletResponse directly.
Harvesting Input
6) Struts 2 uses Action properties as input properties, eliminating the need for a second input object. Input properties may be rich object types which may have their own properties. The Action properties can can be accessed from the web page via the taglibs. Struts 2 also supports the ActionForm pattern, as well as POJO form objects and POJO Actions. Rich object types, including business or domain objects, can be used as input/output objects. The ModelDriven feature simplifies taglb references to POJO input objects.
Expression Language
7) Struts 2 can use JSTL, but the framework also supports a more powerful and flexible expression language called "Object Graph Notation Language" (OGNL).
Binding values into views
8) Struts 2 uses a "ValueStack" technology so that the taglibs can access values without coupling your view to the object type it is rendering. The ValueStack strategy allows reuse of views across a range of types which may have the same property name but different property types.
Type Conversion
9) Struts 2 uses OGNL for type conversion. The framework includes converters for basic and common object types and primitives.
Validation
10) Struts 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
11) Struts 2 supports creating different lifecycles on a per Action basis via Interceptor Stacks. Custom stacks can be created and used with different Actions, as needed.
