Struts Dispatch Action Example
Struts Dispatch Action (org.apache.struts.actions.DispatchAction)
is one of the Built-in Actions provided along with the struts framework.
The org.apache.struts.actions.DispatchAction
class enables a user to collect related functions into a single Action. It eliminates
the need of
creating multiple independent actions for each function. Here in this example
you will learn more about Struts Dispatch Action that will help you grasping the
concept better.
Let's develop Dispatch_Action class which is a sub class of org.apache.struts.actions.DispatchAction
class. This class does not provide an implementation for the execute() method because DispatchAction
class itself implements this method. This class manages to
delegate the request to one of the methods of the derived Action class. An Action Mapping is done to select the
particular method (via
Struts-Configuration file).
Here the Dispatch_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 different
ActionForward like "add" in case of add() method
, "edit" in case of edit() etc.
Each ActionForward is defined in the struts-config.xml file (action mapping is shown later in this page). Here is
the code for Action Class.
Developing an Action Class (Dispatch_Action.java)
package roseindia.net;
import java.io.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.ServletException;
import org.apache.struts.actions.DispatchAction;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
/**
* @author Amit Gupta
* @Web http://www.roseindia.net
* @Email struts@roseindia.net
**/
public class Dispatch_Action extends DispatchAction
{
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");
}
}
|
Developing an ActionForm Class
Our form bean class contains only one property "parameter"
which is playing prime role in this example. Based on the parameter value appropriate
function of Action class is executed. Here is the code for FormBean ( DispatchActionForm.java):
package roseindia.net;
import org.apache.struts.action.ActionForm;
/**
* @author Amit Gupta
* @Web http://www.roseindia.net
* @Email struts@roseindia.net
**/
public class DispatchActionForm extends ActionForm
{
private String parameter =" ";
public String getParameter()
{
return parameter;
}
public void setParameter(String parameter)
{
this.parameter=parameter;
}
}
|
Defining form Bean in struts-config.xml file
Add the following entry in the struts-config.xml file for defining the form bean
<form-bean name="DispatchActionForm"
type="roseindia.net.DispatchActionForm"/>
|
Developing the Action Mapping in the struts-config.xml
Here, Action mapping helps to select the method from the Action class for specific requests. Note that the value specified with the parameter
attribute is used to delegate request to the required method of the
Dispath_Action Class.
<action
path="/DispatchAction"
type="roseindia.net.Dispatch_Action"
parameter="parameter"
input="/pages/DispatchAction.jsp"
name="DispatchActionForm"
scope="request"
validate="false">
<forward name="add" path="/pages/DispatchActionAdd.jsp" />
<forward name="edit" path="/pages/DispatchActionEdit.jsp" />
<forward name="search" path="/pages/DispatchActionSearch.jsp"/>
<forward name="save" path="/pages/DispatchActionSave.jsp" />
</action>
|
Developing jsp page
Code of the jsp (DispatchAction.jsp) to delegate
requests to different jsp pages :
<%@ taglib uri="/WEB-INF/struts-bean.tld" prefix="bean"%>
<%@ taglib uri="/WEB-INF/struts-html.tld" prefix="html"%>
<html:html locale="true">
<HEAD>
<TITLE>Dispatch Action Example</TITLE>
<BODY>
<H3>Dispatch Action Example</H3>
<p><html:link page="/DispatchAction.do?parameter=add">Call Add Section</html:link></p>
<p><html:link page="/DispatchAction.do?parameter=edit">Call Edit Section</html:link></p>
<p><html:link page="/DispatchAction.do?parameter=search">Call Search Section</html:link></p>
<p><html:link page="/DispatchAction.do?parameter=save">Call Save Section</html:link></p>
</html:html>
|
Add the following line in the index.jsp to call the
form.
<li>
<html:link page="/pages/DispatchAction.jsp">Struts File
Upload</html:link>
<br>
Example demonstrates how DispatchAction Class works.
</li>
Building and Testing the Example
To build and deploy the application go to Struts\Strutstutorial
directory and type ant on the command prompt. This will deploy the application.
Open the browser and navigate to the DispatchAction.jsp
page. Your browser displays the following
DispatchAction page.
Selecting Call Add Section
displays the following DispatchActionAdd.jsp page
Selecting Call Edit Section
displays the following DispatchActionEdit.jsp
page
Selecting Call Search Section
displays the following
DispatchActionSearch.jsp page
Selecting Call Save Section
displays the following DispatchActionSave.jsp
page
|
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Current Comments
20 comments so far (post your own) View All Comments Latest 10 Comments:its very helpful ..
Posted by sandeep on Thursday, 05.8.08 @ 09:10am | #58868
hi...i think action is missing in ur dispatchaction.jsp file..go through and send me a correct solution..while executing the programm output came but in linking fashoin just call add section came ..below line not camee.can u find out error and send solution as early as possible..thanks in advance...
Posted by vamsi on Saturday, 04.19.08 @ 10:56am | #57123
I have a small dought can we write multipul methods in Action class like dispatch Action.
In Action class some time we will write two methods execute(),iscancel().
Posted by Mahesh on Monday, 01.7.08 @ 12:35pm | #44693
As far as I know we need to add code for dispatchMethod to dipatch to perticular method.
Do we need this method or not?
Can somebody please clear this confusion?
Posted by Bhushan Chirmade on Friday, 12.28.07 @ 11:49am | #44025
It educed me a lot when concerned with STRUTS.
I whole heartedly appreciate you work for publishing such a valuable information on web.
Posted by vamsi krishna.kunasani on Monday, 12.3.07 @ 20:25pm | #41190
hi
plese someone tell me how to use js files in struts when using dispatchaction
Posted by Raghavendra on Wednesday, 11.21.07 @ 14:37pm | #38152
Hii
I tried this example and when i click on a link i have this error:
HTTP Status 500 - No action instance for path /DispatchAction could be created
message No action instance for path /DispatchAction could be created
description The server encountered an internal error (No action instance for path /DispatchAction could be created) that prevented it from fulfilling this request.
Does anyone know the soluction??
Please it's URGENT!!!!
Posted by layal on Tuesday, 11.20.07 @ 21:23pm | #38079
Examples on how to use DispatchAction
Posted by Srinivas.S on Monday, 11.19.07 @ 12:29pm | #37794
It is good to see the dispatcher action class code and it's site very simple to learn and easy to understand.I really like it this site.
Posted by Harishkumar on Friday, 09.21.07 @ 14:47pm | #28532
good site to get basic idea
Posted by nagesh on Wednesday, 09.12.07 @ 12:15pm | #26825