国外的一些struts面试题（4）

Question: Can I setup Apache Struts to use multiple configuration files?
Answer: Yes Struts can use multiple configuration files. Here is the configuration example:
<servlet>
<servlet-name>banking</servlet-name>
<servlet-class>org.apache.struts.action.ActionServlet
</servlet-class>
<init-param>
<param-name>config</param-name>
<param-value>/WEB-INF/struts-config.xml,
/WEB-INF/struts-authentication.xml,
/WEB-INF/struts-help.xml
</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
Question: What are the disadvantages of Struts?
Answer: Struts is very robust framework and is being used extensively in the industry. But there are some disadvantages of the Struts:
a) High Learning Curve
Struts requires lot of efforts to learn and master it. For any small project less experience developers could spend more time on learning the Struts.
b) Harder to learn
Struts are harder to learn, benchmark and optimize.
Question: What is Struts Flow?
Answer: Struts Flow is a port of Cocoon's Control Flow to Struts to allow complex workflow, like multi-form wizards, to be easily implemented using continuations-capable JavaScript. It provides the ability to describe the order of Web pages that have to be sent to the client, at any given point in time in an application. The code is based on a proof-of-concept Dave Johnson put together to show how the Control Flow could be extracted from Cocoon. (Ref: http://struts.sourceforge.net/struts-flow/index.html )
Question: What are the difference between <bean:message> and <bean:write>?
Answer: <bean:message>: This tag is used to output locale-specific text (from the properties files) from a MessageResources bundle.
<bean:write>: This tag is used to output property values from a bean. <bean:write> is a commonly used tag which enables the programmers to easily present the data.
Question: What is LookupDispatchAction?
Answer: An abstract Action that dispatches to the subclass mapped execute method. This is useful in cases where an HTML form has multiple submit buttons with the same name. The button name is specified by the parameter property of the corresponding ActionMapping. (Ref. http://struts.apache.org/1.2.7/api/org/apache/struts/actions/LookupDispatchAction.html).
Question: What are the components of Struts?
Answer: Struts is based on the MVC design pattern. Struts components can be categories into Model, View and Controller.
Model: Components like business logic / business processes and data are the part of Model.
View: JSP, HTML etc. are part of View
Controller: Action Servlet of Struts is part of Controller components which works as front controller to handle all the requests.
Question: What are Tag Libraries provided with Struts?
Answer: Struts provides a number of tag libraries that helps to create view components easily. These tag libraries are:
a) Bean Tags: Bean Tags are used to access the beans and their properties.
b) HTML Tags: HTML Tags provides tags for creating the view components like forms, buttons, etc..
c) Logic Tags: Logic Tags provides presentation logics that eliminate the need for scriptlets.
d) Nested Tags: Nested Tags helps to work with the nested context.
Question: What are the core classes of the Struts Framework?
Answer: Core classes of Struts Framework are ActionForm, Action, ActionMapping, ActionForward, ActionServlet etc.
Question: What are difference between ActionErrors and ActionMessage?
Answer: ActionMessage: A class that encapsulates messages. Messages can be either global or they are specific to a particular bean property.
Each individual message is described by an ActionMessage object, which contains a message key (to be looked up in an appropriate message resources database), and up to four placeholder arguments used for parametric substitution in the resulting message.
ActionErrors: A class that encapsulates the error messages being reported by the validate() method of an ActionForm. Validation errors are either global to the entire ActionForm bean they are associated with, or they are specific to a particular bean property (and, therefore, a particular input field on the corresponding form).
Question: How you will handle exceptions in Struts?
Answer: In Struts you can handle the exceptions in two ways:
a) Declarative Exception Handling: You can either define global exception handling tags in your struts-config.xml or define the exception handling tags within <action>..</action> tag.
Example:
<exception
key=”database.error.duplicate”
path=”/UserExists.jsp”
type=”mybank.account.DuplicateUserException”/>
b) Programmatic Exception Handling: Here you can use try{}catch{} block to handle the exception.