My Code Snapshots

• Model: Components like business logic /business processes and data are the part of model.
• View: HTML, JSP are the view components.
• Controller: Action Servlet of Struts is part of Controller components which works as front controller to handle all the requests.

• Process user requests
• Determine what the user is trying to achieve according to the request
• Pull data from the model (if necessary) to be given to the appropriate view,
• Select the proper view to respond to the user
• Delegates most of this grunt work to Action classes
• Is responsible for initialization and clean-up of resources

<action-mappings>
 <action path="/submit"
 type="submit.SubmitAction"
         name="submitForm"
         input="/submit.jsp"
         scope="request"
         validate="true">
  <forward name="success" path="/success.jsp"/>
  <forward name="failure" path="/error.jsp"/>
 </action>
</action-mappings>

public ActionForward execute( 
     ActionMapping mapping,
             ActionForm form,
             HttpServletRequest request,
             HttpServletResponse response)
          throws Exception ;

• Perform the processing required to deal with this request
• Update the server-side objects (Scope variables) that will be used to create the next page of the user interface
• Return an appropriate ActionForward object

<servlet>
<servlet-name>action</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-admin.xml,
     /WEB-INF/struts-config-forms.xml          
  </param-value>
</init-param>
.....<servlet>

What is the directory structure of Struts application?

The directory structure of Struts application :

• ForwardAction
• IncludeAction
• DispatchAction
• LookupDispatchAction
• SwitchAction

• Create a class that extends DispatchAction (instead of Action)
• In a new class, add a method for every function you need to perform on the service – The method has the same signature as the execute() method of an Action class.
• Do not override execute() method – Because DispatchAction class itself provides execute() method.
• Add an entry to struts-config.xml

• In struts-config.xml: change your <form-bean> to be an org.apache.struts.action.DynaActionForm instead of some subclass of ActionForm

<form-bean name="loginForm"type="org.apache.struts.action.DynaActionForm" >
    <form-property name="userName" type="java.lang.String"/>
    <form-property name="password" type="java.lang.String" />
</form-bean>

• HTML Tags
• Bean Tags
• Logic Tags
• Template Tags
• Nested Tags
• Tiles Tags

<bean:message key="prompt.customer.firstname"/>

<bean:write name="customer" property="firstName"/>

<table border=1>  
  <logic:iterate id="customer" name="customers"> 
    <tr> 
      <td><bean:write name="customer" property="firstName"/></td> 
      <td><bean:write name="customer" property="lastName"/></td> 
      <td><bean:write name="customer" property="address"/></td> 
   </tr> 
  </logic:iterate> 
</table> 

• Programmatic exception handling :
Explicit try/catch blocks in any code that can throw exception. It works well when custom value (i.e., of variable) needed when error occurs.

• Declarative exception handling :You can either define <global-exceptions> handling tags in your struts-config.xml or define the exception handling tags within <action></action> tag. It works well when custom page needed when error occurs. This approach applies only to exceptions thrown by Actions.

<global-exceptions>
 <exception key="some.key"
            type="java.lang.NullPointerException"
            path="/WEB-INF/errors/null.jsp"/>
</global-exceptions>

<exception key="some.key" 
           type="package.SomeException" 
           path="/WEB-INF/somepage.jsp"/>

• An ActionForm represents an HTML form that the user interacts with over one or more pages. You will provide properties to hold the state of the form with getters and setters to access them. Whereas, using DynaActionForm there is no need of providing properties to hold the state. Instead these properties and their type are declared in the struts-config.xml
• The DynaActionForm bloats up the Struts config file with the xml based definition. This gets annoying as the Struts Config file grow larger.
• The DynaActionForm is not strongly typed as the ActionForm. This means there is no compile time checking for the form fields. Detecting them at runtime is painful and makes you go through redeployment.
• ActionForm can be cleanly organized in packages as against the flat organization in the Struts Config file.
• ActionForm were designed to act as a Firewall between HTTP and the Action classes, i.e. isolate and encapsulate the HTTP request parameters from direct use in Actions. With DynaActionForm, the property access is no different than using request.getParameter( .. ).
• DynaActionForm construction at runtime requires a lot of Java Reflection (Introspection) machinery that can be avoided.