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The following page has been changed by MichaelJouravlev: http://wiki.apache.org/struts/StrutsManualActionWebComponentAsync ------------------------------------------------------------------------------ == Component Configuration == + Same as for [:StrutsManualActionWebComponentSync:synchronous] version. - First let us define the Login Component in {{{struts-config.xml}}} file: - - {{{ - <struts-config> - - <form-beans> - <!-- Login form --> - <form-bean name = "loginform" type="samples.login.LoginForm"/> - </form-beans> - - <action-mappings> - - <!-- Composite page containing login component --> - <action path="/login-struts" - forward="/login-struts/index.jsp"/> - - <!-- Login component --> - <action component = "Login" - view = "/login-struts/loginComponent.jsp" - path = "/logincomponent" - type = "samples.login.LoginAction" - form = "loginform" - scope = "session" - validate = "false"> - <event name="loginEvent" handler="login"/> - <event name="logoutEvent" handler="logout"/> - </action> - - </action-mappings> - </struts-config> - }}} - - Notice action mapping attributes and properties that are new for Struts 1.4: - - * "component" attribute contains the name of a component. This name is used by <comp:component> tag that generates DIV element around component markup. The ID of this DIV is assigned to the component name. When application returns updated markup, Javascript helper matches ID of returned markup with ID of enclosing element in composite page. Another role of component name is to identify an action as a component manager, it is processed differently than a regular action or behavioral action. - * "component" attribute identifies an action as a component manager, such actions are processed differently by Action class. This name is also used in generated HTML for in-place update in Ajax mode. - * "view" attribute identifies a default view for a component. Must be a JSP page. Often consists from several subviews, in our case the Login Component has two subviews "Not Logged In" and "Logged In", they will be defined in JSP file. - * "form" is just another name for "name" property - * "event" property allows to define request parameters as events, and corresponding method handlers. This is made possible by supporting dispatching functionality directly in Action class. == Component Action == + Same as for [:StrutsManualActionWebComponentSync:synchronous] version. Event handlers should always return null, they cannot return an {{{ActionForward}}} object. It is not possible to forward or redirect to another page if request is sent in asynchronous mode. - The action class is deceptively simple. It handles only two events, the corresponding handlers are called automatically by Action class. The location of component's view is defined in the action mapping, so render method is not needed. On the other hand, most non-trivial components need to process data before rendering themselves or to exchange data with other components. For these cases you can use render" method. Its default implementation does nothing. - - {{{ - public class LoginAction extends Action { - - public ActionForward login (ActionMapping mapping, - ActionForm form, - HttpServletRequest request, - HttpServletResponse response) throws Exception { - - HttpSession session = request.getSession(); - LoginForm inputForm = (LoginForm) form; - - // Log out current user first - request.getSession().removeAttribute("USER"); - - // Validation is turned off in struts-config.xml, - // so explicitly validate user input; - ActionMessages errors = inputForm.validate(mapping, request); - - if (errors != null) { - saveErrors(session, errors); - } else { - // Use this session attribute to hold user's name - session.setAttribute("USER", inputForm.getUsername()); - } - - // Always return null. - return null; - } - - public ActionForward logout (ActionMapping mapping, - ActionForm form, - HttpServletRequest request, - HttpServletResponse response) throws Exception { - - LoginForm inputForm = (LoginForm) form; - - // Clean name and password in the input/output form bean - inputForm.setUsername(null); - inputForm.setPassword(null); - - // Remove dialog name from session, effectively logging out - request.getSession().removeAttribute("USER"); - - // Always return null. - return null; - } - } - }}} == Component Form Bean == + Same as for [:StrutsManualActionWebComponentSync:synchronous] version. - Nothing exciting here, just a session-scoped form to hold user name and to validate credentials: - - {{{ - public class LoginForm extends ActionForm { - - private String username; - public String getUsername() {return username;} - public void setUsername(String username) {this.username = username;} - - private String password; - public String getPassword() {return password;} - public void setPassword(String password) {this.password = password;} - - // Generate the error messages in the same manner as usual, - // but do not forget to turn "validate" property of the action mapping off. - public ActionErrors validate(ActionMapping mapping, HttpServletRequest request) { - if (!"guest".equalsIgnoreCase(username) || - !"pass".equalsIgnoreCase(password)) { - ActionErrors errors = new ActionErrors(); - errors.add("ERROR", new ActionMessage("login.badpassword")); - return errors; - } else { - return null; - } - } - } - }}} == Login/Logout JSP page == - The Login/Logout component has two subviews, both defined in one JSP page. Notice that content type is set to "text/xml", this is important for Ajax mode. + The differences from [:StrutsManualActionWebComponentSync:synchronous] version are: + + * content type must be set to "text/xml" + * component markup must be valid XHTML + * Content of JSP file must be wrapped into <comp:component> element + * <html:form> and <html:input> elements must have {{{styleClass}}} attribute set to "strutsCommand", this enables runtime binding of Ajax functionality to these elements. {{{ <%@ page contentType="text/xml;charset=UTF-8" language="java" %> @@ -203, +95 @@ == Composite Page == - Now we need to include the Login Component into a larger page (composite page). This is done with JSTL c:import tag. Do not use jsp:include, it may not work on some containers: + The differences from [:StrutsManualActionWebComponentSync:synchronous] version are: + + * <c:import> that includes a component, must be wrapped into a DIV or another element with ID equal to component name. This ensures that component markup is properly updated in-place. {{{ <%@ page contentType="text/html;charset=UTF-8" language="java" %> @@ -230, +124 @@ == Done! == - This is pretty much it. Now run the application and navigate to composite page. The included component will evaluate user's state and will display a login form. Try to log in. The submitted credentials are sent directly to a component, if they are not correct, the composite page is redisplayed. How? Behind the scenes the improved Action class as well as JSP tags work together to distinguish the address of a composite page during first render. This address is saved automatically. Then after component finishes, it reloads the composite page using saved address. Now you can develop independent Struts components! + Now you can develop independent Struts components!
