Struts%20Interview%20Questions%20and%20Answers

Ques 1. What is Struts?

Struts is a web page development framework and an open source software that helps developers build web applications quickly and easily. Struts combines Java Servlets, Java Server Pages, custom tags, and message resources into a unified framework. It is a cooperative, synergistic platform, suitable for development teams, independent developers, and everyone between.

Ques 2. 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.

Ques 3. Who makes the Struts?

Struts is hosted by the Apache Software Foundation(ASF) as part of its Jakarta project, like Tomcat, Ant and Velocity.

Ques 4. Do we need to pay the Struts if being used in commercial purpose?

No. Struts is available for commercial use at no charge under the Apache Software License. You can also integrate the Struts components into your own framework just as if they were written in house without any red tape, fees, or other hassles.

Ques 5. What are the core classes of Struts?

Action, ActionForm, ActionServlet, ActionMapping, ActionForward are basic classes of Structs.

Ques 6. What is the design role played by Struts?

The role played by Structs is controller in Model/View/Controller(MVC) style. The View is played by JSP and Model is played by JDBC or generic data source classes. The Struts controller is a set of programmable components that allow developers to define exactly how the application interacts with the user.

Ques 7. How Struts control data flow?

Struts implements the MVC/Layers pattern through the use of ActionForwards and ActionMappings to keep control-flow decisions out of presentation layer.

Ques 8. What configuration files are used in Struts?

Ques 9. What helpers in the form of JSP pages are provided in Struts framework?

There are 4 major JSTLs (JSP Standard Tag Libraries) provided in Struts as JSP helpers. Those tag libraries are described in TLD (Tag Library Descriptor) files:

struts-html.tld - Tags to help generating HTML elements.
struts-form.tld - Tags to help generating HTML FORM elements.
struts-bean.tld - Tags representing some JavaBeans like: cookie, header, message, and page.
struts-logic.tld - Tags representing Boolean logic operations.

Ques 10. How you will enable front-end validation based on the xml in validation.xml?

The < html:javascript > tag to allow front-end validation based on the xml in validation.xml. For example the code: < html:javascript formName=logonForm dynamicJavascript=true staticJavascript=true / > generates the client side java script for the form logonForm as defined in the validation.xml file. The < html:javascript > when added in the jsp file generates the client site validation script.

Ques 11. What is ActionServlet?

The class org.apache.struts.action.ActionServlet is the called the ActionServlet. In the the Jakarta Struts Framework this class plays the role of controller. All the requests to the server goes through the controller. Controller is responsible for handling all the requests.
 

Ques 12. 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 < message-resources / > tag. Example: < message-resources parameter= MessageResources / >

Ques 13. What is Action Class?

The Action Class is part of the Model and is a wrapper around the business logic. The purpose of Action Class is to translate the HttpServletRequest to the business logic. To use the Action, we need to Subclass and overwrite the execute() method. In the Action Class all the database/business processing are done. It is advisable to perform all the database related stuffs in the Action Class. 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.

Ques 14. Write code of any Action Class?

Here is the code of Action Class that returns the ActionForward object.
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;

public class TestAction extends Action
{
public ActionForward execute(
ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response) throws Exception
{
return mapping.findForward("testAction");
}
}

Ques 15. What is ActionForm?

An ActionForm is a JavaBean that extends org.apache.struts.action.ActionForm. ActionForm maintains the session state for web application and the ActionForm object is automatically populated on the server side with data entered from a form on the client side.

Ques 16. What is Struts Validator Framework?

Struts Framework provides the functionality to validate the form data. It can be use to validate the data on the users browser as well as on the server side. Struts Framework emits the java scripts and it can be used validate the form data on the client browser. Server side validation of form can be accomplished by sub classing your From Bean with DynaValidatorForm class. The Validator framework was developed by David Winterfeldt as third-party add-on to Struts. Now the Validator framework is a part of Jakarta Commons project and it can be used with or without Struts. The Validator framework comes integrated with the Struts Framework and can be used without doing any extra settings.

Ques 17. Is Struts compatible with other Java technologies?

Yes. Struts is committed to supporting industry standards. Struts acts as an integrator of Java technologies so that they can be used in the real world.

Ques 18. Who wrote Struts?

There are several active committers to the Struts project, working cooperatively from around the globe. Dozens of individual developers and committers contributed to the Struts 1.x codebase. All interested Java developers are invited to contribute to the project. Struts is a Apache Software Foundation project, with the mission to "provide secure, enterprise-grade server solutions based on the Java Platform that are developed in an open and cooperative fashion".
Struts was created by Craig R. McClanahan and donated to The Apache Software Foundation in May 2000. Craig was the primary developer of both Struts 1.x and Tomcat 4. Tomcat 4 was the basis for the official reference implementation for a servlet 2.3 and JSP 1.2 container.
Craig's current focus is as architect of the Sun Java Studio Creator (formerly Project Rave). Craig also serves as the Specification Lead for JavaServer Faces (JSR-127), and is the Web Layer Architect for the Java2 Enterprise Edition (J2EE) platform as a whole. 

Ques 19. How do I install Struts?

To develop applications with Struts, you can usually just add the Struts JAR file to your Java development environment. You can then start using the Struts classes as part of your own application. A blank Struts application (in the webapps directory, open struts-blank.war) is provided, which you can just copy to get a quick-start on your own brainchild.
Since the full source code for Struts is available, we also provide complete instructions for compiling your own Struts JAR from scratch. (This is actually easier than it looks!)
Your Struts application can usually be deployed using a standard WAR file. In most cases, you simply deposit the WAR file on your application server, and it is installed automatically. If not, step-by-step installation instructions for various servlet containers are available.

Ques 20. When do I need "struts.jar" on my classpath?

When you are compiling an application that uses the Struts classes, you must have the "struts.jar" on the classpath your compiler sees -- it does not have to be on your CLASSPATH environment variable.
Why is that an important distinction? Because if you are using a servlet container on your development machine to test your application, the "struts.jar" must not be on your CLASSPATH environment variable when running the container. (This is because each Web application must also have their own copy of the Struts classes, and the container will become confused if it is on the environment path as well.)
There are several general approaches to this issue:
* Use ANT for building your projects -- it can easily assemble classpaths for the compiler. (This is how Struts itself is built, along with Tomcat and most other Java-based projects).
* Use an IDE where you can configure the "class path" used for compilation independent of the CLASSPATH environment variable.
* Use a shell script that temporarily adds struts.jar to the classpath just for compilation, for example javac -classpath /path/to/struts.jar:$CLASSPATH $@

Ques 21. Does Struts include its own unit tests?

Struts currently has two testing environments, to reflect the fact that some things can be tested statically, and some really need to be done in the environment of a running servlet container.
For static unit tests, we use the JUnit framework. The sources for these tests are in the "src/test" hierarchy in the source repository, and are executed via the "test.junit" target in the top-level build.xml file. Such tests are focused on the low-level functionality of individual methods, are particularly suitable for the static methods in the org.apache.struts.util utility classes. In the test hierarchy, there are also some "mock object" classes (in the org.apache.struts.mock package) so that you can package up things that look like servlet API and Struts API objects to pass in as arguments to such tests.
Another valuable tool is Struts TestCase which provides a useful harness for Action classes that can be used with JUnit or Cactus.

Ques 22. Where can I get help with Struts?

The Struts package comes complete with a Users Guide to introduce people to the framework and its underlying technologies. Various components also have their own in-depth Developers Guide, to cover more advanced topics. Comprehensive Javadocs are included along with the full source code. For your convenience, these are bundled together as a self-installing application. The struts-documentation.war is the same bundle that is deployed as the Struts Web site.
The Strut's mailing list is also very active, and welcomes posts from new users. Before posting a new question, be sure to consult the MAILING LIST ARCHIVE and the very excellent How To Ask Questions The Smart Way by Eric Raymond. Please do be sure to turn off HTML in your email client before posting.

Ques 23. What's the difference between Struts and Turbine? What's the difference between Struts and Espresso?

If you are starting from scratch, packages like Turbine and Espresso can be very helpful since they try to provide all of the basic services that your team is likely to need. Such services include things like data persistence and logging.
If you are not starting from scratch, and need to hook up your web application to an existing infrastructure, then "plain vanilla" Struts can be a better choice. The core Struts framework does not presuppose that you are using a given set of data persistence, presentation, or logging tools. Anything goes =:0)
Compared to other offerings, Struts endeavors to be a minimalist framework. We try leverage existing technologies whenever we can and provide only the missing pieces you need to combine disparate technologies into a coherent application. This is great when you want to select your own tools to use with Struts. But, if you prefer a more integrated infrastructure, then packages like Turbine or Espresso (which uses Struts) are perfectly good ways to go.
See also
* < http://www.mail-archive.com/struts-user@jakarta.apache.org/msg03206.html >
* < http://www.mail-archive.com/general@jakarta.apache.org/msg00495.html >
* < http://jakarta.apache.org/velocity/ymtd/ymtd.html >

Ques 24. Why aren't the Struts tags maintained as part of the Jakarta Taglibs project?

Development of both products began about the same time. Leading up to the release of 1.0, it was thought better to continue to develop the taglibs alongside the controller. Now that 1.0 is out, the JavaServer Pages Standard Taglib is in active development. Once work on JSTL stabilizes, the Struts taglibs will be revisited. Tags which are not linked directly to the framework may be hosted at Jakarta Taglibs instead.

Ques 25. What about JSTL and JavaServer Faces ?

JSTL, the JavaServer Standard Tag Library, is a set of JSP tags that are designed to make it easier to develop Web applications. JavaServer Faces (JSF) is a specification for a new technology that promises to make it easier to write MVC applications, both for the Web and for the desktop.
The inventor of Struts, Craig McClanahan, is the specification co-lead for JavaServer Faces (JSR 127), and architect of the reference implemenation as well as Java Studio Creator. Both JSTL and JSF are complementary to Struts.
The mainstay of the Struts framework is the controller components, which can be used with any Java presentation technology. As new technologies become available, it is certain that new "glue" components will also appear to help these technologies work as well with Struts.
Struts originally came bundled with a set of custom JSP tags. Today, several extensions are available to help you use Struts with other popular presentation technologies, like XSLT and Velocity. Likewise, extensions for JSTL and JSF are now available as well.
The JSTL reference implementation is available through the Jakarta Taglibs site. A JSTL taglibs for Struts, Struts-El , is available and distributed with Struts beginning with the 1.1 release.
The JSF specification and reference implementation is available through Sun's The JSF specification and reference implementation is available through Sun's Java ServerFaces page. An early-release JavaServer Faces taglib for Struts, Struts-Faces, is also in early release and available through the nightly build. The Struts Faces taglib is expected to work with any compliant JSF implementation, including MyFaces.

Ques 26. Is there a particularly good IDE to use with Struts

Struts should work well with any development environment that you would like to use, as well as with any programmers editor. The members of the Struts development team each use their own tools such as Emacs, IDEA, Eclipse, and NetBeans.

Ques 27. Can I use JavaScript to submit a form?

You can submit a form with a link as below. BTW, the examples below assume you are in an block and 'myForm' is picked up from the struts-config.xml name field of the action.

onclick='document.forms["myForm"].myAction.value="save";
document.forms["myForm"].submit();' />
onclick='document.forms["myForm"].myAction.value="delete";
document.forms["myForm"].submit();' />
... the java part ...
class MyAction extends ActionForm implements Serializable {

public ActionForward execute (ActionMapping map, ActionForm form,
HttpServletRequest req, HttpServletResponse) {

String myAction = req.getParameter("myAction");

if (myAction.equals("save") {
// ... save action ...
} else if (myAction.equals("delete") {
// ... delete action ...
}
}
}
}
This is just one of many ways to achieve submitting a form and decoding the intended action. Once you get used to the framework you will find other ways that make more sense for your coding style and requirements. Just remember this example is completely non-functional without JavaScript.

Ques 43. 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. How you will display validation fail errors on jsp page? - The following tag displays all the errors: < html:errors/ >

Ques 44. How does Struts work?

Java Servlets are designed to handle requests made by Web browsers. Java ServerPages are designed to create dynamic Web pages that can turn billboard sites into live applications. Struts uses a special Servlet as a switchboard to route requests from Web browsers to the appropriate ServerPage. This makes Web applications much easier to design, create, and maintain.

Ques 45. Are the Struts tags XHTML compliant ?

If you use an <html:html xhtml="true> or <html:xhtml/> element on your page, the tags will render as XHTML (since Struts 1.1).

Ques 46. Do ActionForms have to be true JavaBeans?

The utilities that Struts uses (Commons-BeanUtils since 1.1) require that ActionForm properties follow the JavaBean patterns for mutators and accessors (get*,set*,is*). Since Struts uses the Introspection API with the ActionForms, some containers may require that all the JavaBean patterns be followed, including declaring "implements Serializable" for each subclass. The safest thing is to review the JavaBean specification and follow all the prescribed patterns.
Since Struts 1.1, you can also use DynaActionForms and mapped-backed forms, which are not true JavaBeans. For more see ActionForm classes in the User Guide and Using Hashmaps with ActionForms in this FAQ.

Ques 47. Can I use multiple HTML form elements with the same name?

Yes. Define the element as an array and Struts will autopopulate it like any other.
private String[] id= {};
public String[] getId() { return this.id; }
public void setItem(String id[]) {this.id = id;}
And so forth

Ques 48. Why are my checkboxes not being set from ON to OFF?

A problem with a checkbox is that the browser will only include it in the request when it is checked. If it is not checked, the HTML specification suggests that it not be sent (i.e. omitted from the request). If the value of the checkbox is being persisted, either in a session bean or in the model, a checked box can never unchecked by a HTML form -- because the form can never send a signal to uncheck the box. The application must somehow ascertain that since the element was not sent that the corresponding value is unchecked.
The recommended approach for Struts applications is to use the reset method in the ActionForm to set all properties represented by checkboxes to null or false. The checked boxes submitted by the form will then set those properties to true. The omitted properties will remain false. Another solution is to use radio buttons instead, which always submit a value.
It is important to note that the HTML specification recommends this same behavior whenever a control is not "successful". Any blank element in a HTML form is not guaranteed to submitted. It is therefor very important to set the default values for an ActionForm correctly, and to implement the reset method when the ActionForm might kept in session scope.

Ques 49. Why do the Struts tags provide for so little formatting?

The Struts tags seem to provide only the most rudimentary functionality. Why is there not better support for date formatting and advanced string handling?
Three reasons:
First, work started on the JSTL and we didn't want to duplicate the effort.
Second, work started on Java Server Faces, and we didn't want to duplicate that effort either.
Third, in a Model 2 application, most of the formatting can be handled in the ActionForms (or in the business tier), so all the tag has to do is spit out a string. This leads to better reuse since the same "how to format" code does not need to be repeated in every instance. You can "say it once" in a JavaBean and be done with it. Why don't the Struts taglibs offer more layout options?
Since the Struts tags are open source, you can extend them to provide whatever additional formatting you may need. If you are interested in a pre-written taglib that offers more layout options, see the struts-layout taglib.
In the same arena, there is a well regarded contributor taglib that can help you create Menus for your Struts applications.

Ques 50. Why does the option tag render selected=selected instead of just selected?

Attribute minimization (that is, specifying an attribute with no value) is a place where HTML violates standard XML syntax rules. This matters a lot for people writing to browsers that support XHTML, where doing so makes the page invalid. It's much better for Struts to use the expanded syntax, which works the same on existing browsers interpreting HTML, and newer browsers that expect XHTML-compliant syntax. Struts is following the behavior recommended by the XHTML specification.

<select id="item" name="item" selected="selected">
<option value="option1">Option1</option>
<option value="option2">Option2</option>
</select>

Ques 51. Do I have to use JSPs with my application?

The short answer to this question is: No, you are not limited to JavaServer Pages.
The longer answer is that you can use any type of presentation technology which can be returned by a web server or Java container. The list includes but is not limited to:
* JavaServer Pages,
* HTML pages,
* WML files,
* Java servlets,
* Velocity templates, and
* XML/XLST
Some people even mix and match apparently unrelated technologies, like PHP, into the same web application.

Ques 52. Can I have an Action without a form?

Yes. If your Action does not need any data and it does
not need to make any data available to the view or
controller component that it forwards to, it doesn't need
a form. A good example of an Action with no ActionForm is
the LogoffAction in the struts example application:


<action path="/logoff"
type="org.apache.struts.webapp.example.LogoffAction">
<forward name="success" path="/index.jsp"/>
</action>

This action needs no data other than the user's session, which
it can get from the Request, and it doesn't need to prepare any
view elements for display, so it does not need a form.


However, you cannot use the <html:form> tag without
an ActionForm. Even if you want to use the <html:form>
tag with a simple Action that does not require input,
the tag will expect you to use some type of ActionForm,
even if it is an empty subclass without any properties.

Ques 53. Can you give me a simple example of using the requiredif Validator rule?

First off, there's an even newer Validator rule called
validwhen, which is almost certainly what you want to use,
since it is much easier and more powerful.
It will be available in the first release after 1.1 ships.
The example shown below could be coded with validwhen as:

Ques 54. When is the best time to validate input?

This is an excellent question. Let's step back a second and think about a typical mid to large size application. If we start from the back end and work toward the view we have:
1) Database: Most modern databases are going to validate for required fields, duplicate records, security constraints, etc.
2) Business Logic: Here you are going to check for valid data relationships and things that make sense for the particular problem you are triing to solve.
... This is where struts comes into the picture, by now the system should be pretty well bulletproof. What we are going to do is make validation friendlier and informative. Rember it is OK to have duplicate validations...
3) ActionErrors validate(ActionMapping map, HttpServletRequest req) is where you can do your validation and feed back to the view, information required to correct any errors. validate is run after the form has been reset and after the ActionForm properties have been set from corresponding view based input. Also remember you can turn validation off with validate="false" in the action mapping in the struts-config.xml. This is done by returning an ActionErrors collection with messages from your ApplicationResources.properties file.
Here you have access to the request so you can see what kinds of action is being requested to fine tune your validations. The <html:error> tag allows you to dump all errors on your page or a particular error associated with a particular property. The input attribute of the struts-config.xml action allows you to send validation errors to a particular jsp / html / tile page.
4) You can have the system perform low level validations and client side feedback using a ValidatorForm or its derivatives. This will generate javascript and give instant feedback to the user for simple data entry errors. You code your validations in the validator-rules.xml file. A working knowledge of regular expressions is necessary to use this feature effectively.

Ques 55. Declarative Exception Handling

If you have developed web applications long enough, you will realize a recurring pattern emerges: when the backend (e.g. the EJB tier) throws you an exception, you nearly always need to display an error page corresponding to the type of that exception. Sooner or later, you will come up with a mechanism to use a lookup table (e.g. an HashMap) to lookup an error page from the exception class.
Struts 1.1 now provides a similar but more powerful mechanism to declare exception handling. In Struts 1.1, you can declare in the struts-config.xml the associations between an exception class and an exception handler. Using the default exception handler included in Struts, you can also specify the path of the error pages. With this information, Struts will automatically forward to the specified pages when an uncaught exception is thrown from an Action.
Like other facilities in Struts, the exception handlers are pluggable. You can write and define your own handler classes if needed. 

Ques 56. Multiple Sub-applications

One of the shortcomings in Struts 1.0 is manageability of the configuration file (commonly known as struts-config.xml) when the development of the application involves a sizable team. This problem arises because a Struts-based application must run under one controller servlet, the ActionServlet, and the ActionServlet can use only one struts-config.xml. It is not an issue when the project is relatively small and the team consists of a couple of developers; however, when the project size becomes significant and the project involves a large number of developers, maintaining all the mapping information in a single file becomes increasingly problematic.
Struts 1.1 solves this problem nicely by introducing multiple sub-applications. In Struts 1.1, each sub-application has its own struts-config.xml file. A large Struts-based application can thus be easily partitioned into largely independent modules, i.e. sub-applications, and each sub-team can maintain their struts-config.xml independently.
The sub-application scheme is a natural extension of the servlet context mapping scheme of the URI paths used by servlet containers. According to the Servlet standard, when the servlet container receives a request with a URL, the servlet container will try to match the prefix of the URI path to a deployed web-application in the container. What Struts 1.1 does is it maps the second prefix of the path to a sub-application. In effect, this prefix mapping scheme creates another level of namespace for each sub-application. For example, for the URI,
http://some-host.com/myApp/module2/editSubscription.do
/myApp is the context path for a web-application called "myApp" and /module2 is the sub-app prefix for a Struts sub-application called "module2".

Ques 57. DynaBean and BeanUtils

Another major complaint usually heard amongst Struts 1.0 users is the extensive effort involved in writing the FormBean (a.k.a. ActionForm) classes.
Struts provides two-way automatic population between HTML forms and Java objects, the FormBeans. To take advantage of this however, you have to write one FormBean per HTML form. (In some use cases, a FormBean can actually be shared between multiple HTML forms. But those are specific cases.) Struts' FormBean standard follows faithfully the verbose JavaBean standard to define and access properties. Besides, to encourage a maintainable architecture, Struts enforces a pattern such that it is very difficult to 'reuse' a model-layer object (e.g. a ValueObject from the EJB tier) as a FormBean. Combining all these factors, a developer has to spend a significant amount of time to write tedious getters/setters for all the FormBean classes.
Struts 1.1 offers an alternative, Dynamic ActionForms, which are based on DynaBeans. Simply put, DynaBeans are type-safe name-value pairs (think HashMaps) but behave like normal JavaBeans with the help of the BeanUtils library. (Both the DynaBeans and the BeanUtils library were found to be useful and generic enough that they have been 'promoted' into Jakarta's Commons project.) With Dynamic ActionForms, instead of coding the tedious setters/getters, developers can declare the required properties in the struts-config.xml files. Struts will instantiate and initialize Dynamic ActionForm objects with the appropriate metadata. From then onwards, The Dynamic ActionForm instance is treated as if it is an ordinary JavaBean by Struts and the BeanUtils library. 

Ques 58. Default Sub-application

To maintain backward compatibility, Struts 1.1 allows one default sub-application per application. The URI of the resources (i.e. JSPs, HTMLs, etc) in the default sub-application will have an empty sub-app prefix. This means when an existing 1.0 application is "dropped" into Struts 1.1, theoretically, it will automatically become the default sub-application.

Ques 59. Why it called Struts?

Because the designers want to remind us of the invisible underpinnings that hold up our houses, buildings, bridges, and ourselves when we are on stilts. This excellent description of Struts reflect the role the Struts plays in developing web applications.

Ques 60. Is Struts efficient?

The Struts is not only thread-safe but thread-dependent(instantiates each Action once and allows other requests to be threaded through the original object.
ActionForm beans minimize subclass code and shorten subclass hierarchies
The Struts tag libraries provide general-purpose functionality
The Struts components are reusable by the application
The Struts localization strategies reduce the need for redundant JSPs
The Struts is designed with an open architecture--subclass available
The Struts is lightweight (5 core packages, 5 tag libraries)
The Struts is open source and well documented (code to be examined easily)
The Struts is model neutral

Ques 61. Why do we need Struts?

Java technologies give developers a serious boost when creating and maintaining applications to meet the demands of today's public Web sites and enterprise intranets. Struts combines Java Servlets, Java ServerPages, custom tags, and message resources into a unified framework. The end result is a cooperative, synergistic platform, suitable for development teams, independent developers, and everyone in between.

Ques 62. Why is it called Struts?

It's a reference to struts in the architectural sense, a reminder of the nearly invisible pieces that hold up buildings, houses, and bridges.

Ques 63. Do I have to credit Struts on my own website?

You need to credit Struts if you redistribute your own framework based on Struts for other people to use. (See the Apache License for details.) But you do not need to credit Struts just because your web application utilizes the framework. It's the same situation as using the Apache HTTPD server or Tomcat. Not required if its just running your web site.

Ques 64. Where can I get a copy of Struts?

The best place to download Struts is at struts.apache.org. The nightly builds are very stable, and recommended as the best place to start today.

Ques 65. If the framework doesn't do what I want, can I request that a feature be added?

First, it's important to remember that Struts is an all-volunteer project. We don't charge anyone anything to use Struts. Committers and other developers work on Struts because they need to use it with their own applications. If others can use it too, that's "icing on the cake". If you submit a patch for a feature that a Committer finds useful, then that Committer may choose to volunteer his or her time to apply the patch. If you just submit an idea without a patch, it is much less likely to be added (since first someone else has to volunteer their time to write the patch).
We are grateful for any patches, and we welcome new ideas, but the best way to see that something gets added to the framework is to do as much of the work as you can, rather than rely on the "kindness of strangers". Worst case, you can apply the patch to your copy of Struts and still use the feature in your own application. (Which is what open source is ~really~ all about.)

Ques 66. Will the Struts tags support other markup languages such as WML  ?

Struts itself is markup neutral. The original Struts taglibs are only one example of how presentation layer components can access the framework. The framework objects are exposed through the standard application, session, and request contexts, where any Java component in the application can make use of them.
Markup extensions that use Struts are available for Velocity and XLST, among others. A new Struts tag library for Java Server Faces is also in development.
For more about using WAP/WML with Struts see the article WAP up your EAserver.

Ques 67. Why was reload removed from Struts (since 1.1)?

The problem with ReloadAction was that Struts was trying to act like a container, but it couldn't do a proper job of it. For example, you can't reload classes that have been modified, or (portably) add new classes to a running web application (even if the container supported it).
Meanwhile, as Struts 1.1 was being developed, work progressed on things like Tomcat's reload command via the Manager webapp. This feature allows you to quickly reload-on-demand, complete with saving and restoring your session). It started to make even less sense for Struts to half-implement a feature that containers are implementing fully.
A more minor point is that freezing the configuration information at application startup time allows Struts to safely access the mapping information without bothering with synchronization. The "startup-only" strategy creates a modest but real improvement in performance for all users.
So, ReloadAction is not supported since Struts 1.1 for two reasons:
* It never did let you reload everything that you would really want to -- particularly changed classes -- so many people ended up having to reload the webapp anyway.
* Containers are starting to offer reload-on-demand features which does the same thing as the Struts ReloadAction, only better.
* Not supporting ReloadAction lets Struts avoid doing synchronization locks around all the lookups (like figuring out which action to use, or the destination of an ActionForward) so applications can run a little faster.
Of course, if someone came up with an implementation that solved these problems without creating any others, we would not be opposed to including a new ReloadAction.

Ques 68. What is a modular application? What does module-relative mean?

Since Struts 1.1, the framework supports multiple application modules. All applications have at least one root, or default, module. Like the root directory in a file system, the default application has no name. (Or is named with an empty string, depending your viewpoint.) Developing an application with only a default module is no different from how applications were developed under Struts 1.0. Since Struts 1.1, you can add additional modules to your application, each of which can have their own configuration files, messages resources, and so forth. Each module is developed in the same way as the default module. Applications that were developed as a single module can added to a multiple module application, and modules can promoted to a standalone application without change. For more about configuring your application to support multiple modules, see Configuring Applications in the User Guide.
But to answer the question =:0), a modular application is a Struts application that uses more than one module. Module-relative means that the URI starts at the module level, rather than at the context level, or the absolute-URL level.
* Absolute URL: http://localhost/myApplication/myModule/myAction.do
* context-relative: /myModule/myAction.do
* module-relative: /myAction.do
The Struts Examples application is a modular application that was assembled from several applications that were created independently.

Ques 69. Why are some of the class and element names counter-intuitive?

The framework grew in the telling and, as it evolved, some of the names drifted.
The good thing about a nightly build, is that everything becomes available to the community as soon as it is written. The bad thing about a nightly build is that things like class names get locked down early and then become difficult to change.

Ques 70. Why is ActionForm a base class rather than an interface?

The MVC design pattern is very simple to understand but much more difficult to live with. You just need this little bit of Business Logic in the View logic or you need just that little bit of View logic in the Business tier and pretty soon you have a real mess.
Making ActionForm a class takes advantage of the single inheritance restriction of Java to it makes it more difficult for people to do things that they should not do.
ActionForms implemented as interfaces encourage making the property types match the underlying business tier instead of Strings, which violates one of the primary purposes for ActionForms in the first place (the ability to reproduce invalid input, which is a fundamental user expectation). ActionForms as an interface would also encourage using existing DAO objects as ActionForms by adding 'implements ActionForm' to the class. This violates the MVC design pattern goal of separation of the view and business logic.
Since the goal of struts is to enforce this separation, it just makes more sense for Struts to own the ActionForm.
DynaActionForms relieve developers of maintaining simple ActionForms. For near zero maintenance, try Niall Pemberton's LazyActionForm

Ques 71. Why doesn't the focus feature on the <html:form> tag work in every circumstance?

Unfortunately, there is some disagreement between the various browsers, and different versions of the same browser, as to how the focus can be set. The <html:form> tag provides a quick and easy JavaScript that will set the focus on a form for most versions of most browsers. If this feature doesn't work for you, then you should set the focus using your own JavaScript. The focus feature is a convenient "value-add" -- not a core requirement of the tag. If you do come up with a JavaScript that provides the final solution to this project, please post your patch to this Bugzilla ticket.

Ques 72. Can't I just create some of my JavaBeans in the JSP using a scriptlet?

Struts is designed to encourage a Model 2/MVC architecture. But there is nothing that prevents you from using Model 1 techniques in your JavaServer Pages, so the answer to the question is "Yes, you can".
Though, using Model 1 techniques in a Struts application does go against the grain. The approach recommended by most Struts developers is to create and populate whatever objects the view may need in the Action, and then forward these through the request. Some objects may also be created and stored in the session or context, depending on how they are used.
Likewise, there is nothing to prevent you from using scriptlets along with JSP tags in your pages. Though, many Struts developers report writing very complex scriplet-free applications and recommend the JSP tag approach to others.
For help with Model 1 techniques and scriptlets, you might consider joining the Javasoft JSP-interest mailing list, where there are more people still using these approaches.

Ques 73. How do I use JavaScript to struts?

.
Struts is mainly a server-side technology. We bundled in some JSP tags to expose the framework components to your presentation page, but past that, the usual development process applies.
Interactive pages require the use of JavaScript. (That's why it was invented.) If you want things popping up or doing this when they click that, you are outside the scope of Struts and back into the web development mainstream.
You use JavaScript with Struts the same way you use with any presentation page. Since JavaScript is a client-side technology, you can use simple relative references to your scripts. If you need to fire a JavaScript from a HTML control, the Struts HTML tags have properties for the JavaScript events.
A very good JavaScript resource is Matt Kruse's site at http://www.mattkruse.com/javascript/ Do I need to implement reset and set all my form properties to their initial values?
No. You need to set checkbox properties to false if the ActionForm is being retained in session scope. This is because an unchecked box does not submit an attribute. Only checked boxes submit attributes. If the form is in session scope, and the checkbox was checked, there is no way to turn it back off without the reset method. Resetting the properties for other controls, or for a request scope form, is pointless. If the form is in request scope, everything already just started at the initial value.

Ques 74. Can I use other beans or hashmaps with ActionForms?

Yes. There are several ways that you can use other beans or hashmaps with ActionForms.
* ActionForms can have other beansor hashmaps as properties
* "Value Beans" or "Data Transfer Objects" (DTOs) can be used independently of ActionForms to transfer data to the view
* ActionForms can use Maps to support "dynamic" properties (since Struts 1.1)
ActionForms (a.k.a. "form beans") are really just Java beans (with a few special methods) that Struts creates and puts into session or request scope for you. There is nothing preventing you from using other beans, or including them in your form beans. Here are some examples:
Collections as properties Suppose that you need to display a pulldown list of available colors on an input form in your application. You can include a string-valued colorSelected property in your ActionForm to represent the user's selection and a colorOptions property implemented as a Collection (of strings) to store the available color choices. Assuming that you have defined the getters and setters for the colorSelected and colorOptions properties in your orderEntryForm form bean, you can render the pulldown list using:
<html:select property="colorSelected">
<html:options property="colorOptions" name="orderEntryForm"/>
</html:select>
The list will be populated using the strings in the colorOptions collection of the orderEntryForm and the value that the user selects will go into the colorSelected property that gets posted to the subsequent Action. Note that we are assuming here that the colorOptions property of the orderEntryForm has already been set.
See How can I prepopulate a form? for instructions on how to set form bean properties before rendering edit forms that expect properties to be pre-set.
Independent DTO An Action that retrieves a list of open orders (as an ArrayList of Order objects) can use a DTO independently of any form bean to transfer search results to the view. First, the Action's execute method performs the search and puts the DTO into the request:
ArrayList results = businessObject.executeSearch(searchParameters);
request.setAttribute("searchResults",results);
Then the view can iterate through the results using the "searchResults" request key to reference the DTO:
` <logic:iterate id="order" name="searchResults" type="com.foo.bar.Order">
<tr><td><bean:write name="order" property="orderNumber"/><td>
<td>..other properties...</td></tr>
</logic:iterate>

Ques 75. How can I scroll through list of pages like the search results in google?

Many Struts developers use the Pager from the JSPTags site.
http://jsptags.com/tags/navigation/pager/

Ques 76. Why does the <html:link> tag URL-encode javascript and mailto links?

The <html:link> tag is not intended for use with client-side references like those used to launch Javascripts or email clients. The purpose of link tag is to interject the context (or module) path into the URI so that your server-side links are not dependent on your context (or module) name. It also encodes the link, as needed, to maintain the client's session on the server. Neither feature applies to client-side links, so there is no reason to use the <html:link> tag. Simply markup the client-side links using the standard tag.

Ques 77. How can I avoid validating a form before data is entered?

The simplest way is to have two actions. The first one has the job of setting the form data, i.e. a blank registration screen. The second action in our writes the registration data to the database. Struts would take care of invoking the validation and returning the user to the correct screen if validation was not complete.
The EditRegistration action in the struts example application illustrates this:
< action path="/editRegistration">
type="org.apache.struts.webapp.example.EditRegistrationAction"
attribute="registrationForm"
scope="request"
validate="false">


When the /editRegistration action is invoked, a registrationForm is created and added to the request, but its validate method is not called. The default value of the validate attribute is true, so if you do not want an action to trigger form validation, you need to remember to add this attribute and set it to false.

Ques 78. How can I create a wizard workflow?

The basic idea is a series of actions with next, back, cancel and finish actions with a common bean. Using a LookupDispatchAction is reccomended as it fits the design pattern well and can be internationalized easily. Since the bean is shared, each choice made will add data to the wizards base of information. A sample of struts-config.xml follows:

< form-beans>
<form-bean name="MyWizard"
type="forms.MyWizard" />
</form-beans>

<!-- the first screen of the wizard (next action only available) -->
<!-- no validation, since the finish action is not available -->
<actions>
<action path="/mywizard1"
type="actions.MyWizard"
name="MyWizard"
validate="false"
input="/WEB-INF/jsp/mywizard1.jsp">
<forward name="next"
path="/WEB-INF/jsp/mywizard2.jsp" />
<forward name="cancel"
path="/WEB-INF/jsp/mywizardcancel.jsp" />
</action>

<!-- the second screen of the wizard (back, next and finish) -->
<!-- since finish action is available, bean should validated, note
validation should not necessarily validate if back action requested, you
might delay validation or do conditional validation -->
<action path="/mywizard2"
type="actions.MyWizard"
name="MyWizard"
validate="true"
input="/WEB-INF/jsp/mywizard2.jsp">
<forward name="back"
path="/WEB-INF/jsp/mywizard1.jsp" />
<forward name="next"
path="/WEB-INF/jsp/mywizard3.jsp" />
<forward name="finish"
path="/WEB-INF/jsp/mywizarddone.jsp" />
<forward name="cancel"
path="/WEB-INF/jsp/mywizardcancel.jsp" />
</action>

<!-- the last screen of the wizard (back, finish and cancel only) -->
<action path="/mywizard3"
type="actions.MyWizard"
name="MyWizard"
validate="true"
input="/WEB-INF/jsp/mywizard3.jsp">
<forward name="back"
path="/WEB-INF/jsp/mywizard2.jsp" />
<forward name="finish"
path="/WEB-INF/jsp/mywizarddone.jsp" />
<forward name="cancel"
path="/WEB-INF/jsp/mywizardcancel.jsp" />
</action>


The pieces of the wizard are as follows:
forms.MyWizard.java - the form bean holding the information required
actions.MyWizard.java - the actions of the wizard, note the use of LookupDispatchAction allows for one action class with several methods. All the real work will be done in the 'finish' method.
mywizard[x].jsp - the data collection jsp's
mywizarddone.jsp - the 'success' page
mywizardcancel.jsp - the 'cancel' page

Ques 79. What's the best way to deal with migrating a large application from Struts to JSF? Is there any tool support that can help?

This is a complicated task depending on your Struts application. Because the two frameworks have different goals, there are some challenges. Migrate your response pages first. Keep the Struts controller and place and forward to JSF pages. Then you can configure Struts forwards to go through the Faces servlet. Consider looking at the Struts-Faces framework from Apache. See the framework chapter in JSF in Action. 

Ques 80. How can I 'chain' Actions?

Chaining actions can be done by simply using the
proper mapping in your forward entries in the struts-config.xml file.
Assume you had the following two classes:


/* com/AAction.java */
...

public class AAction extends Action
{
public ActionForward
execute(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response) throws
Exception
{
// Do something

return mapping.findForward("success");
}
}



/* com/BAction.java */
...

public class BAction extends Action
{
public ActionForward
execute(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response) throws
Exception
{
// Do something else

return mapping.findForward("success");
}
}


Then you can chain together these two actions with
the Struts configuration as shown in the following excerpt:


...

type="com.AAction"
validate="false">


type="com.BAction"
scope="session"
validate="false">



...


Here we are assuming you are using a suffix-based (.do) servlet mapping, which is recommended since module support requires it. When you send your browser to the web application and name the action A.do (i.e. http://localhost:8080/app/A.do) it will execute AAction.execute(), which will then forward to the "success" mapping.
This causes the execution of BAction.execute() since the entry for "success" in the configuration file uses the .do suffix.
Of course it is also possible to chain actions programmatically, but the power and ease of being able to "reroute" your web application's structure using the XML configuration file is much easier to maintain.
As a rule, chaining Actions is not recommended. If your business classes are properly factored, you should be able to call whatever methods you need from any Action, without splicing them together into a cybernetic Rube Goldberg device.
If you must chain Actions, be aware of the following: calling the second Action from the first Action has the same effect as calling the second Action from scratch. If both of your Actions change the properties of a formbean, the changes made by the first Action will be lost because Struts calls the reset() method on the formbean when the second Action is called.

Ques 81. Struts GenericDataSource Just a general question - I'm building an application that will run stand-alone, not in an application server. I need to manage some database connections. Is the struts GenericDataSource a good candidate to do this for me? I basicly just need a connection pool from where I can get connections and then return them to optimize performance.
If this struts class is not a good candidate, can someone recommend a similar pool-manager that is lean and mean and easy to use?

Answer 1
The Struts 1.0 GenericDataSource is not a good candidate for a production server. In Struts 1.1, the Commons DBCP is used istead, which is a good candidate for a production server. (You can also use the DBCP in Struts 1.0 by specifying the type and including the Commons JARs.)
Another popular choice is Poolman. It's not under active development, but I believe you can still download it from SourceForge. Poolman is also very easy to use outside of Struts.
Many containers also offer support for connection pools. The one that ships with Resin is quite good. The later versions of Tomcat bundle the Commons DBCP.
Regardless of what pool you use, a good practice is to hide it behind some type of adaptor class of your own (often a singleton), to make it easy to change later. So your classes call your adaptor, and your adaptor calls whichever pool you are using.
A neat and often-overlooked aspect of the Struts DataSource manager is that it supports loading multiple connection pools and giving each a name. So you might have one pool for internal use and another for public use. This way, the public connections can't swap your administrative access to the application. Each pool could also have its own login, and therefore different rights to the underlying database.
Answer 2


int i=1;

with Struts 1.0 and jdbc i'am use GenericDataSource
not in struts-xml, but in Client.properties

my Client.properties
instanceBd=oraID
userPasswd=xxx/yyyy
maxCount=20
minCount=19
port=1521
driver=oracle.jdbc.driver.OracleDriver
url=jdbc:oracle:thin:@serverName:port:instanceBd

then, on my code i have init (struts 1.0 or struts 1.1):

GenericDataSource ng = new GenericDataSource ();

ng.setUser (mprop.getUserBd());
ng.setPassword (mprop.getPasswdBd());
ng.setUrl (mprop.getUrl());
ng.setDriverClass(mprop.getDriverClass());
ng.setMaxCount(mprop.getMaxCount());
ng.setMinCount (mprop.getMinCount());
ng.setDescription("jdbc OracleDriver");
ng.setAutoCommit(true);
try { ng.open(); } catch (java.sql.SQLException e) {
}


in business logic (or pool) :
Connect cn = ng.getConnection();

it's work.

with struts 1.1 , struts-legacy.jar is necessy for this codes.

it's work.

Ques 82. Is it possible to create the elements of a page(jsp) dynamically based on the results of a data base query, when using struts framework?

If you are talking about rendering a report, then sure. The Action iteracts with the business layer/data access objects to acquire the data, and then passes it to the presentation page bundled up as a JavaBean or a collection of JavaBeans. The JSP tags (and other systems) all use reflection, so you can use whatever JavaBean you like.
If you are talking about creating a dynamic data-entry form, then "not so much".
Struts 1.1 supports map-backed ActionForms, but the page still needs to know what input fields are going to be needed. For a truly dynamic input form, I guess the key would be some type of tag that took a map and then generated a column of input fields. (Wouldn't work for everyone, since a lot of forms must be designed just so.) For extra credit, the entry names could (optionally) be resource keys that were used to find the label text.
Text fields would be easy. Others would need some type of JavaBean with properties to tell the tag what to output. A bit of work, but obviously doable.
Of course, you'd probably want to validate the form before passing it back to the database. I imagine it's possible to use the validator in a non-declarative way, but I don't know anyone whose doing that. If you can do a db query to get the information about the form, I imagine you could also do a query to get the information about validations for the form. It would probably be easier to write your own engine than adopt the validator. (It's not really that complicated to do.)
People often ask about "dynamic input forms", but most of us just can't get our head around the use case. It's hard to understand what you do with the dynamic data when it comes back. Most application don't allow you to input or update an arbitrary (e.g. dynamic) set of fields.

Ques 83. Both JSF and Struts will continue to exist for a while. The Struts community is aware of JSF and is positioning itself to have strong support for JSF. See What about JSTL and JavaServer faces?

From a tools perspective, if you look at the support for JSF versus Struts in WebSphere Studio, the Struts tools are focused around the controller aspects. The Web Diagram editor helps build your Struts configuration and the wizards/editors build Struts artifacts. The JSF tools are geared towards building pages, and in essence, hide the JSF framework from you. Expect WebSphere Studio to support both frameworks for a while. As JSF matures, expect to see some of the controller aspects in JSF to become toolable.

Ques 84. Can you compare the advantages and disadvantages of JSF vs. Struts. Both now, and from what you may know of futures, how and if JSF will evolve into a superior technology vs. Struts? Include how WSAD plays into the comparison if it will help differentiate the two.

This is a very popular question these days. In general, JSF is still fairly new and will take time to fully mature. However, I see JSF being able to accomplish everything Struts can, plus more. Struts evolved out of necessity. It was created by developers who were tired of coding the same logic again and again. JSF emerged both from necessity and competition.
Struts has several benefits:
* Struts is a mature and proven framework. It has been around for a few years and deployed successfully on many projects. The WebSphere Application Server admin console is a Struts application.
* Struts uses the Front Controller and Command patterns and can handle sophisticated controller logic.
* In addition to the core controller function, it has many add-on benefits such as layouts with Tiles, declarative exception handling, and internationalization.

There are disadvantages:

* Struts is very JSP-centric and takes other frameworks to adapt to other view technologies.
* Although Struts has a rich tag library, it is still geared towards helping the controller aspect of development and does not give a sense that you are dealing with components on a page. Therefore, it is not as toolable from a view perspective.
* Struts requires knowledge of Java?. Its goal was to aid Java developers, but not to hide Java. It does not hide details of the Java language to Web developers that well.
* ActionForms are linked programmatically to the Struts framework. Therefore, to decouple the model, you need to write transfer code or use utilities to move data from Action Forms to the Model on input.

JSF is an evolution of a few frameworks, including Struts. The creator of Struts, Craig McClanahan, is one of the JSF specification leads. Therefore, it is not by accident to see some overlap between Struts and JSF. However, one of JSF's major goals is to help J2EE Web applications to be easily developed using RAD tools. As such, it introduces a rich component model. JSF has several advantages:
* JSF is a specification from Sun® and will be included in future versions of the J2EE specification. All major vendors are pledging strong support for JSF.
* JSF uses the Page Controller Pattern and therefore aids in Page rich applications. Components can respond to event from components on a page.
* JSF has a well-defined request lifecycle allowing for plugability at different levels.
* One powerful example of plugability is building your own render toolkit. The ability to separate the rendering portion from the controller portion of the framework allows for wonderful opportunities of extensibility. Component providers can write their own toolkits to render different markup languages, such as XML or WML. In addition, the render toolkit is not tied to JSP.
* Because JSF has a rich component model, it favors a RAD style of development. I can now build my Web pages using drag and drop technology. In addition, JSF gives me a way to link visual components to back model components without breaking the layering.
JSF has disadvantages:
* JSF is still quite new and evolving. It will take some time to see successful deployments and wide usage. In addition, as vendors write components, they may not do everything you want them to.
* JSF by hand is not easier than Struts. Its goal was more oriented to RAD. Those who prefer to do things by hand (for example, the vi type guy who does not like IDEs) may find Struts easier to develop.
* Struts navigation may be a bit more flexible and adhere to more complex controller logic.