LookupDispatchAction

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LookupDispatchAction

LookupDispatchAction is another useful built-in Struts Action. When a set of actions is closely related and separating them into multiple Actions would result in duplication of code you can use LookupDispatchAction. LookupDispatchAction is subclass of DispatchAction.
In case of DispatchAction, you have to declare the method name in the JSP page.
For Example :
http://localhost:8080/emp/empaction.do?step=add // IN CASE OF DispatchAction
here step=add , we are delaring method name in JSP.
or
<html:submit property="step">Add</html:submit> //IN CASE OF DispatchAction
so we can't use localization for button in case of DispatchAction.
To over come both the issues below
a)method name declaration in JSP
b)can't use localization for button
We will go for LookupDispatchAction.

For example : If there are three operation like delete, activate, deactivate employee. You can create three different Actions �
ActivateEmpAction, DeleteEmpAction and DeActivateEmpAction.
This is a valid approach, although not elegant since there might be duplication of code across the Actions since they are related. LookupDispatchAction is the answer to this problem. With LookupDispatchAction, you can combine all three Actions into one.

Follow the below six steps to setup LookupDispatchAction.

Step 1. In the JSP page (empdetails.jsp)

<%@ taglib uri="/WEB-INF/struts-tiles.tld" prefix="tiles" %>
<%@ taglib uri="/WEB-INF/struts-html.tld" prefix="html" %>
<%@ taglib uri="/WEB-INF/struts-bean.tld" prefix="bean" %>
<%@ taglib uri="/WEB-INF/struts-logic.tld" prefix="logic" %>
<html:form>
<html:form action="/saveEmp" method="post">
<html:submit property="step">
<bean:message key="button.activate"/>
</html:submit>
<html:submit property="step">
<bean:message key="button.delete"/>
</html:submit>
<html:submit property="step">
<bean:message key="button.deactivate"/>
</html:submit>
</html:form>

//No need method name declaration in JSP . Button name from resource bundle.

Step 2. In the the Resource Bundle. //Here you can add localization.

button.activate=Activate
button.delete=Delete
button.deactivate=DeActivate

Step 3. Adding ActionForm Entry in struts-config.xml

Add the following entry in the struts-config.xml file.

<form-bean name="EmpForm"
         type="com.techfaq.form.EmpForm">

</form-bean>

Step 4. Add action mapping in the struts-config.xml file:

Add the following action mapping in the struts-config.xml file:

Step 5. In the Action class.

Implement a method named getKeyMethodMap() in the subclass of the LookupDispatchAction. The method returns a java.util.Map. The keys used in the Map should be also used as keys in Message Resource Bundle.

public class EmpAction extends LookupDispatchAction {

					public Map getKeyMethodMap()

{

Map map = new HashMap();

map.put("button.activate", "activate");

map.put("button.delete", "delete");

map.put("button.deactivate", "deactivate");

}

public ActionForward activate(ActionMapping mapping,

ActionForm form, HttpServletRequest request,

HttpServletResponse response) throws Exception

{

//your logic

mapping.findForward("activate-success");

}


public ActionForward delete(ActionMapping mapping,

ActionForm form, HttpServletRequest request,

HttpServletResponse response) throws Exception

{

//your logic

mapping.findForward("delete-success");

}

public ActionForward deactivate(ActionMapping mapping,

ActionForm form, HttpServletRequest request, 

HttpServletResponse response) throws Exception

{
//your logic

mapping.findForward("deactivate-success");

}


}

Step 6. In the EmpForm


               public class EmpForm extends ActionForm {

				   int empId;

				   String firstName;

				   	public String getFirstName() {

					return firstName;

					}

	
					public void setFirstName(String firstName) {

					this.firstName = firstName;

					}


					public int getEmpId() {

					return empId;

					}

	
					public void setEmpId(int empId) {

					this.empId = empId;

					}

				}

Now in the browser type http://localhost:8080/jsp/empdetails.jsp

for every form submission, LookupDispatchAction does the reverse lookup on the resource bundle to get the key and then gets the method whose name is associated with the key from getKeyMethodmap().
Flow of LookupDispatchAction:
a) Form the button name "Delete" get the key "button.delete" fro resource bundle.
b) then in the Map getKeyMethodMap() find the value associated with the key "button.delete".
c) value from the Map is "delete" . then call delete() method of the same action class.