In this lesson I will show you how to use Struts Action Class and forward a jsp file through it.
What is Action Class?
An Action class in the struts application extends Struts 'org.apache.struts.action.Action" Class. Action class acts as wrapper around the business logic and provides an inteface to the application's Model layer. It acts as glue between the View and Model layer. It also transfers the data from the view layer to the specific business process layer and finally returns the procssed data from business layer to the view layer.
An Action works as an adapter between the contents of an incoming HTTP request and
the business logic that corresponds to it. Then the struts controller (ActionServlet)
slects an appropriate Action and creates an instance if necessary, and finally
calls execute method.
To use the Action, we need to Subclass and overwrite the execute() method. In the Action Class don't add the business process logic, instead move the database and business process logic to the process or dao layer.
The ActionServlet (commad) passes the parameterized class to Action Form using the execute() method. The return type of the execute method is ActionForward which is used by the Struts Framework to forward the request to the file as per the value of the returned ActionForward object.
Developing our Action Class?
Our Action class (TestAction.java) is simple class that only forwards the TestAction.jsp. Our Action class returns the ActionForward called "testAction", which is defined in the struts-config.xml file (action mapping is show later in this page). Here is code of our Action Class:
Understanding Action Class
Here is the signature of the Action Class.
public ActionForward execute(ActionMapping mapping, ActionForm form, javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws java.lang.Exception
Action Class process the specified HTTP request, and
create the corresponding HTTP response (or forward to another web component that
will create it), with provision for handling exceptions thrown by the business
logic. Return an
ActionForward instance describing where and how
control should be forwarded, or
null if the response has already
mapping- The ActionMapping used to select this instance
form- The optional ActionForm bean for this request (if any)
request- The HTTP request we are processing
response- The HTTP response we are creating
Action class throws java.lang.Exception- if the application business logic throws an exception
Adding the Action Mapping in the struts-config.xml
To test the application we will add a link in the index.jsp
<html:link page="/TestAction.do">Test the Action</html:link>
Following code under the <action-mappings> tag is used to for mapping the TestAction class.
<action path="/TestAction" type="roseindia.net.TestAction"> <forward name="testAction" path="/pages/TestAction.jsp"/> </action>
To test the new application click on Test the Action link on the index page. The content of TestAction.jsp should be displayed on the user browser.
In this lesson you learned how to create Action Class and add the mappings in the struts-config.xml. Our Action Class returns the ActionForward mapping of the TestAction.jsp.
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