Struts Framework Interview Questions And Answers
Jakarta Apache Struts 2 is an elegant, extensible framework for creating enterprise-ready Java web applications. The framework is designed to streamline the full development cycle, from building, to deploying, to maintaining applications over time.
Apache Struts 2 was originally known as WebWork 2. After working independently for several years, the WebWork and Struts communities joined forces to create Struts2. This new version of Struts is simpler to use and closer to how Struts was always meant to be.
1. Can I setup Apache Struts to use multiple configuration files?
Yes Struts can use multiple configuration files. Here is the configuration example: banking org.apache.struts.action.ActionServlet config /WEB-INF/struts-config.xml, /WEB-INF/struts-authentication.xml, /WEB-INF/struts-help.xml 1
2. Give the Details of XML files used in Validator Framework?
The Validator Framework uses two XML configuration files validator-rules.xml and validation.xml. The validator-rules.xml defines the standard validation routines, these are reusable and used in validation.xml. to define the form specific validations. The validation.xml defines the validations applied to a form bean.
3. How is the MVC design pattern used in Struts framework?
In the MVC design pattern, application flow is mediated by a central Controller. The Controller delegates requests to an appropriate handler. The handlers are tied to a Model, and each handler acts as an adapter between the request and the Model. The Model represents, or encapsulates, an application?s business logic or state. Control is usually then forwarded back through the Controller to the appropriate View. The forwarding can be determined by consulting a set of mappings, usually loaded from a database or configuration file. This provides a loose coupling between the View and Model, which can make an application significantly easier to create and maintain. Controller: Servlet controller which supplied by Struts itself; View: what you can see on the screen, a JSP page and presentation components; Model: System state and a business logic JavaBeans.
4. How Struts relates to J2EE?
Struts framework is built on J2EE technologies (JSP, Servlet, Taglibs), but it is itself not part of the J2EE standard.
5. how to execute the business operation associated with the requested action.
In the Struts framework this helper class is descended of org.apache.struts.action.Action class. It acts as a bridge between a client-side user action and business operation. The Action class decouples the client request from the business model. This decoupling allows for more than one-to-one mapping between the user request and an action. The Action class also can perform other functions such as authorization, logging before invoking business operation. the Struts Action class contains several methods, but most important method is the execute() method. public ActionForward execute(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception; The execute() method is called by the controller when a request is received from a client. The controller creates an instance of the Action class if one doesn?t already exist. The strut framework will create only a single instance of each Action class in your application. Action are mapped in the struts configuration file and this configuration is loaded into memory at startup and made available to the framework at runtime. Each Action element is represented in memory by an instance of the org.apache.struts.action.ActionMapping class . The ActionMapping object contains a path attribute that is matched against a portion of the URI of the incoming request. path= "/somerequest" type="com.somepackage.someAction" scope="request" name="someForm" validate="true" input="somejsp.jsp" Once this is done the controller should determine which view to return to the client. The execute method signature in Action class has a return type org.apache.struts.action.ActionForward class. The ActionForward class represents a destination to which the controller may send control once an action has completed. Instead of specifying an actual JSP page in the code, you can declaratively associate as action forward through out the application. The action forward are specified in the configuration file. path= "/somerequest" type="com.somepackage.someAction" scope="request" name="someForm" validate="true" input="somejsp.jsp" The action forward mappings also can be specified in a global section, independent of any specific action mapping. public interface RequestDispatcher
6. How you will display validation fail errors on jsp page?
The following tag displays all the errors:
7. How you will enable front-end validation based on the xml in validation.xml?
The tag to allow front-end validation based on the xml in validation.xml. For example the code: generates the client side java script for the form ?logonForm? as defined in the validation.xml file. The when added in the jsp file generates the client site validation script.
8. How you will make available any Message Resources Definitions file to the Struts Framework Environment?
Message Resources Definitions file are simple .properties files and these files contains the messages that can be used in the struts project. Message Resources Definitions files can be added to the struts-config.xml file through tag. Example:
9. I plugged in a version of Apache Xalan that I downloaded from the Apache Web site, and now I get errors when I try to transform documents. What is the problem?
You must ensure that the version of Apache Xalan you download from the Apache Web site is compatible with Apache Xerces version 1.3.1. Because you cannot plug in a different version of Apache Xerces (see the preceding Question:), the only version of Apache Xerces that is compatible with WebLogic Server 6.1 is 1.3.1. The built-in parser (based on version 1.3.1 of Apache Xerces) and transformer (based on version 2.0.1 of Apache Xalan) have been modified by BEA to be compatible with each other.
10. Is struts threadsafe? Give an example?
Struts is not only thread-safe but thread-dependant. The response to a request is handled by a light-weight Action object, rather than an individual servlet. Struts instantiates each Action class once, and allows other requests to be threaded through the original object. This core strategy conserves resources and provides the best possible throughput. A properly-designed application will exploit this further by routing related operations through a single Action.
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