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The following page has been changed by MichaelJouravlev: http://wiki.apache.org/struts/StrutsQuickStart2 ------------------------------------------------------------------------------ == Event handling in Struts: delete an employee == + + Now after you got the idea how Struts fits the servlet/JSP environment, let us improve our application. How about being able to delete an employee from the list? To do this we will change the JSP page, adding an "Operation" column and creating a "Delete" link for each table row. The link would contain employee ID. When clicked, the link will be processed by the same Action that displays the list. inline:employee_list_delete.gif - Now after you got the idea how Struts fits the servlet/JSP environment, let us improve our application. How about being able to delete an employee from the list? To do this we will change the JSP page, adding an "Operation" column and creating a "Delete" link for each table row. The link would contain employee ID. When clicked, the link will be processed by the same Action that displays the list. To distinguish the "Delete" command from the request to merely display the list, we will add a special parameter to the link. We will define this parameter as an event for this action in the {{{struts-config.xml}}} file, and we will redesign the Action class to perform employee removal code when this parameter is received. + There are two different approaches to processing the "Delete" link: either to create a separate action class and refer to this action from the link, or to handle employee removal in the same action that displays action list. First approach is more traditional, while the second allows to have less action classes and less mappings in the config file, it is used in this guide. + To process different requests, an Action class should be able to distinguish between different request types. In case of this application, there are two request types: + + * First request type does not have any query parameters and means "show me the employee list". + * Second request type has a special request parameter that means "delete an employee with ID passed along in this request". + + We will use "deleteEvent" query parameter as a command to delete an employee. This parameter will be added to "Delete" links. We will define this parameter as an event in the {{{struts-config.xml}}} file, and we will redesign the Action class to perform employee removal when this parameter is received. + + Let us start with the configuration file. Action events are defined in "parameter" attribute of an action mapping as "key=value" pairs. In this example, when "deleteEvent" parameter is present in the request, Struts will run {{{delete}}} method on the !EmployeesListAction class. + + {{{<action path = "/employeesList" + type = "actions.EmployeesListAction" + parameter = "deleteEvent=delete"> + <forward name = "render" path = "/pages/employees.jsp"/> + <forward name = "finished" path = "/employeesList.do" redirect = "true"/> + </action>}}} + - Here is modified EmployeeListAction class, notice that it extends EventDispatchAction class: + Now let us modify EmployeeListAction class by extending EventDispatchAction class: + - {{{public class EmployeesListActionDelete extends EventDispatchAction { + {{{public class EmployeesListAction extends EventDispatchAction { /** * Handles "deleteEvent" event (see struts-config.xml file). Deletes an employee @@ -56, +75 @@ } }}} - Now the definition of "Delete" event in the action mapping in {{{struts-config.xml}}} file: - {{{<action path = "/employeesListDelete" - type = "actions.EmployeesListActionDelete" - parameter = "deleteEvent=delete"> - <forward name = "render" path = "/jspstruts2/employees.jsp"/> - <forward name = "finished" path = "/employeesListDelete.do" redirect = "true"/> - </action>}}} - - The "parameter" attribute states that if "deleteEvent" request parameter is received, then "delete" method of EmployeesListActionDelete should be called. Also notice two mappings, "render" and "finished". First is used to display employee list, second is used to finish processing of "deleteEvent" event and to redisplay the item list by redirecting to it. - - Finally, the JSP. Notice the <html:link> tag to create a link, JSTL 2.0 is used for convenience: + Finally, the JSP. Notice the <html:link> tag to create a link, JSTL 2.0 is used to create link parameters: {{{<%@ page contentType="text/html;charset=UTF-8" language="java" %> <%@ taglib uri="http://struts.apache.org/tags-html"; prefix="html" %> <html:html> <body> + <table> <tr> <th align="left">Emp #</th> @@ -89, +99 @@ </tr> </c:forEach> </table> + </body> </html:html>}}}
