The struts 2 framework is used to develop MVC-based web application.
The struts framework was initially created by Craig McClanahan and donated to Apache Foundation in May, 2000 and Struts 1.0 was released in June 2001.
The current stable release of Struts is Struts 2.3.16.1 in March 2, 2014.
This struts 2 tutorial covers all the topics of Struts 2 Framework with simplified examples for beginners and experienced persons.
Struts 2 Framework
The Struts 2 framework is used to develop MVC (Model View Controller) based web applications. Struts 2 is the combination ofwebwork framework of opensymphony and struts 1.
The Struts 2 provides supports to POJO based actions, Validation Support, AJAX Support, Integration support to various frameworks such as Hibernate, Spring, Tiles etc, support to various result types such as Freemarker, Velocity, JSP etc.
Struts 2 provides many features that were not in struts 1. The important features of struts 2 framework are as follows:
- Configurable MVC components
- POJO based actions
- AJAX support
- Integration support
- Various Result Types
- Various Tag support
- Theme and Template support
1) Configurable MVC components
In struts 2 framework, we provide all the components (view components and action) information in struts.xml file. If we need to change any information, we can simply change it in the xml file.
2) POJO based actions
In struts 2, action class is POJO (Plain Old Java Object) i.e. a simple java class. Here, you are not forced to implement any interface or inherit any class.
3) AJAX support
Struts 2 provides support to ajax technology. It is used to make asynchronous request i.e. it doesn't block the user. It sends only required field data to the server side not all. So it makes the performance fast.
4) Integration Support
We can simply integrate the struts 2 application with hibernate, spring, tiles etc. frameworks.
5) Various Result Types
We can use JSP, freemarker, velocity etc. technologies as the result in struts 2.
6) Various Tag support
Struts 2 provides various types of tags such as UI tags, Data tags, control tags etc to ease the development of struts 2 application.
7) Theme and Template support
Struts 2 provides three types of theme support: xhtml, simple and css_xhtml. The xhtml is default theme of struts 2. Themes and templates can be used for common look and feel.
Before developing the web applications, we need to have idea about design models. There are two types of programming models (design models)
- Model 1 Architecture
- Model 2 (MVC) Architecture
Model 1 Architecture
Servlet and JSP are the main technologies to develop the web applications.
Servlet was considered superior to CGI. Servlet technology doesn't create process, rather it creates thread to handle request. The advantage of creating thread over process is that it doesn't allocate separate memory area. Thus many subsequent requests can be easily handled by servlet.
Problem in Servlet technology Servlet needs to recompile if any designing code is modified. It doesn't provide separation of concern. Presentation and Business logic are mixed up.
JSP overcomes almost all the problems of Servlet. It provides better separation of concern, now presentation and business logic can be easily separated. You don't need to redeploy the application if JSP page is modified. JSP provides support to develop web application using JavaBean, custom tags and JSTL so that we can put the business logic separate from our JSP that will be easier to test and debug.
As you can see in the above figure, there is picture which show the flow of the model1 architecture.
- Browser sends request for the JSP page
- JSP accesses Java Bean and invokes business logic
- Java Bean connects to the database and get/save data
- Response is sent to the browser which is generated by JSP
Advantage of Model 1 Architecture
- Easy and Quick to develop web application
Disadvantage of Model 1 Architecture
- Navigation control is decentralized since every page contains the logic to determine the next page. If JSP page name is changed that is referred by other pages, we need to change it in all the pages that leads to the maintenance problem.
- Time consuming You need to spend more time to develop custom tags in JSP. So that we don't need to use scriptlet tag.
- Hard to extend It is better for small applications but not for large applications.
Model 2 (MVC) Architecture
Model 2 is based on the MVC (Model View Controller) design pattern. The MVC design pattern consists of three modules model, view and controller.
Model The model represents the state (data) and business logic of the application.
View The view module is responsible to display data i.e. it represents the presentation.
Controller The controller module acts as an interface between view and model. It intercepts all the requests i.e. receives input and commands to Model / View to change accordingly.
Advantage of Model 2 (MVC) Architecture
- Navigation control is centralized Now only controller contains the logic to determine the next page.
- Easy to maintain
- Easy to extend
- Easy to test
- Better separation of concerns
Disadvantage of Model 2 (MVC) Architecture
- We need to write the controller code self. If we change the controller code, we need to recompile the class and redeploy the application.
Visit here to get the Example of MVC using Servlet and JSP.
Solution of Model 2 Architecture: Configurable MVC Components
It uses the declarative approach for defining view components, request mapping etc. It resolves the problem of Model 2 architecture. The Struts framework provides the configurable MVC support. In struts 2, we define all the action classes and view components in struts.xml file.
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