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Struts MappingDispatchAction Example

Struts MappingDispatch Action (org.apache.struts.actions.MappingDispatchAction) isone of the Built-in Actions provided along with the struts framework.

The org.apache.struts.actions.MappingDispatchAction class is a subclass of

org.apache.struts.actions.DispatchAction class. This class enables a user to collect

related functions into a single action class. It needs to create multiple independentactions for each function. Here in this example you will learn more about Struts

MappingDispatchAction that will help you to grasp the concept better.

Let's develop a class MappingDispatch_Action which is a sub class

oforg.apache.struts.actions.MappingDispatchAction class. This class does notprovide an implementation for the execute() method because DispatchAction class itself

implements this method.

MappingDispatchAction class is much like the DispatchAction class except that it uses

a unique action corresponding to a new request, to dispatch the methods . At run time,this class manages to delegate the request to one of the methods of the derived Action

class. Selection of a method depends on the value of the parameter passed from the

incoming request. MappingDispatchAction uses this request parameter value and selectsa corresponding action from the different action-mappings defined. This eliminates the

need of creating an instance of ActionForm class.

MappingDispatch_Action class contains multiple methods ie.. add() , edit() , search() ,

save() . Here all the methods are taking the same input parameters but each method

returns a differentActionForwardlike "add" in case ofadd() method , "edit" in case ofedit() etc. Each ActionForward is defined in the struts-config.xml file (action mapping is

shown later in this page).

Developing an Action Class (MappingDispatch_Action.java)

package roseindia.net;

/*** @author Amit Gupta* @Web http://www.roseindia.net

* @Email struts@roseindia.net**/

import java.io.*;import java.util.*;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.ServletException;import org.apache.struts.actions.MappingDispatchAction;

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import org.apache.struts.action.ActionForm;import org.apache.struts.action.ActionForward;import org.apache.struts.action.ActionMapping;

public class MappingDispatch_Action extends MappingDispatchAction{

public ActionForward add( ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception{ System.out.println("You are in add function."); return mapping.findForward("add"); }

public ActionForward edit( ActionMapping mapping, ActionForm form,

HttpServletRequest request, HttpServletResponse response) throws Exception{ System.out.println("You are in edit function."); return mapping.findForward("edit"); }

public ActionForward search( ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception{ System.out.println("You are in search function"); return mapping.findForward("search");

}public ActionForward save( ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception{ System.out.println("You are in save function"); return mapping.findForward("save"); }

}

No need to Develop an ActionForm Class

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Developing the Action Mapping in the struts-config.xml

Here, we need to create multiple independent actions for each method defined in theaction class. Note that the value specified with the parameter attributeis used to

delegate request to the required method of the MappingDispatch_Action Class.

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Developing jsp page

Code of the jsp (MappingDispatchAction.jsp) to delegate requests to different jsp pages :

Mapping Dispatch Action Example

Dispatch Action Example

Call Add Section

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Selecting Call Add Section displays the following MappingDispatchActionAdd.jsp

page

Selecting Call Edit Section displays the following MappingDispatchActionEdit.jsp

page

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Selecting Call Search Section displays the

following MappingDispatchActionSearch.jsppage

Selecting Call Save Section displays the following MappingDispatchActionSave.jsp

page