INTERVIEW QUESTIONS J2EE STRUTS DETAILS

Question: Explain Struts navigation flow?

Answer: Struts Navigation flow.

1) A request is made from previously displayed view.
2) The request reaches the ActionServlet which acts as the controller .The ActionServlet Looksup the requested URI in an XML file (Struts-Config.xml) and determines the name of the Action class that has to perform the requested business logic.
3)The Action Class performs its logic on the Model Components associated with the Application.
4) Once The Action has been completed its processing it returns the control to the Action Servlet.As part of its return the Action Class provides a key to determine where the results should be forwarded for presentation.
5)The request is complete when the Action Servlet responds by forwarding the request to the view, and this view represents the result of the action.

Submitted by Vemuri Rama Krishna (iamvemuri @ yahoo . com )

Struts Navigation flow.

1) A request is made from previously displayed view.
2) The request reaches the ActionServlet which acts as the controller .The ActionServlet Looksup the requested URI in an XML file (Struts-Config.xml) and determines the name of the Action class that has to perform the requested business logic.
3)The Action Class performs its logic on the Model Components associated with the Application.
4) Once The Action has been completed its processing it returns the control to the Action Servlet.As part of its return the Action Class provides a key to determine where the results should be forwarded for presentation.
5)The request is complete when the Action Servlet responds by forwarding the request to the view, and this view represents the result of the action.

Submitted by Vemuri Rama Krishna (iamvemuri @ yahoo . com ) Source: CoolInterview.com

1.when ever user requests for something the control goes to the WEB.XML and checks the config info.
2.then the action form will be called and then reset() method will be called followed by validate() if and only if "validate" attribute of action definition in struts-config.xml is set true(action form does only field validations)
3.if the field validations are correct, appropriate action class will be selected from the struts-config.xml action definition. the execute() method will be called in the action class.
4.suppose the user has only 2 fields "username" "password"
actionform validates whether he has entered something or not. and now action class execute() method refers whether the user entered correct username and password.
if it was correct it will be forwared to success page. Source: CoolInterview.com

Struts Navigation flow
-----------------------

Step-1 : At first when the application is started in the server the web.xml file will load and parsed.

Step-2: when request comes to the context or application, it will find out which servlet need to execute with the respective request, By default in Struts based we applications the ActionServlet is the receiver of every request so the container invokes the ActionServlet by using the “web.xml” file details.

Ex:
<servlet>
<servlet-name>MyController</servlet-name>
<servlet-class>org.apache.struts.action.ActionServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>MyController</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping>



Step-3: At first it will check whether the ActionServlet object is initialized or not if not it will create the ActionServlet object and initialize it.
Step-4: In the ActionServlet initialization, it'll do the following things

It will create the ModuleConfig object with the struts configuration file details (struts-config.xml) and create the RequestProcessor object and invokes RequestProcessor initialization method with “ModuleConfig” and “ActionServlet” objects as parameters to it.
Ex:
init( actionservlet,moduleConfig);

NOTE: We can do all this initialization steps at the begins of the server or application by using the <load-on-startup> tag in the “web.xml” file for the ActionServlet.

Step-5: If the ActionServlet is already initialized then the container will invokes the “doGet/doPost” method of the ActionServlet to process the request. In that doGet/doPost it simple transfer the controller to the RequestProcessor “execute” method.

Step-6: For processing the request the RequestProcessor “execute” method calls a sequence of “procesXXX()” methods.

Few of the main processXXX() methods are :

I)processPath(): Identify and return the path component (from the request URI) that we will use to select an ActionMapping with which to dispatch. If no such path can be identified, create an error response and return null
II)processContent(): Set the default content type (with optional character encoding) for all responses if requested. NOTE - This header will be overridden automatically if a RequestDispatcher.forward call is ultimately invoked
III)processActionForm(): Retrieve and return the ActionForm associated with this mapping, creating and retaining one if necessary. If there is no ActionForm associated with this mapping, return null.
IV)processActionCreate():Return an Action instance that will be used to process the current request, creating a new one if necessary
V)processActionPerform():Ask the specified Action instance to handle this request. Return the ActionForward instance (if any) returned by the called Action for further processing.
VI)processForwardConfig(): Forward or redirect to the specified destination, by the specified mechanism. This method uses a ForwardConfig object instead an ActionForward.

Step-7: At last the RequestProcessor “destroy()” method will invokes to destroy all the Action class objects.

Step-8: After that the ActionServlet “destroy” method will invoke to destroy all the Modules and RequestProcessor objects

Step-9: Destroy the ActionServlet object.

Step-10: At the time of application getting shutdown the ActionServlet class will unload Source: CoolInterview.com

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