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The following page has been changed by MichaelJouravlev: http://wiki.apache.org/struts/StrutsManualActionWebComponentSync New page: == Struts Component Lifecycle In Synchronous Mode == In synchronous mode the component lifecycle is managed in a five-step process: 1. The cycle begins with the initial load of a composite page, starting the render phase. 2. When the JSP processor encounters a <c:import> action in a composite page, it generates an HTTP request to obtain the content of the included component. 3. The Action class forwards to a view relevant to component state. After all components on the composite page have rendered themselves, the render phase finishes and a composite page is presented to a user. 4. The user initiates the input phase by submitting an HTML form or by activating a command link. The browser sends input data to an Action that manages component events and state. The Action processes data and updates component state if needed. Component state can be stored in a session-scoped form bean, in a database or in other location. 5. After input data has been processed, the Action automatically redirects to location of the composite page, effectively switching from input phase back to render phase. Steps 1 through 3 are repeated, and an updated page is presented to the user. nline:action_component_title.gif == Component Configuration == 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 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 == 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 == 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. {{{ <%@ page contentType="text/xml;charset=UTF-8" language="java" %> <%@ page import="java.util.ArrayList, org.apache.struts.Globals"%> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"; %> <%@ taglib uri="http://struts.apache.org/tags-bean"; prefix="bean" %> <%@ taglib uri="http://struts.apache.org/tags-html"; prefix="html" %> <%@ taglib uri="http://struts.apache.org/tags-logic"; prefix="logic" %> <%@ taglib uri="http://struts.apache.org/tags-comp"; prefix="comp" %> <comp:component> <%-- "Not Logged In" subview --%> <c:if test='${empty USER}'> <h3>Please Log In</h3> <!-- Displaying Struts errors --> <logic:messagesPresent> <html:messages id="error"> <li><bean:write name="error"/></li> </html:messages> </logic:messagesPresent><br/> <%-- "strutsCommand" CSS class is a hook for Ajax-mode handler, it is set in runtime using Behaviour library. --%> <html:form method="get" styleClass="strutsCommand" action="/loginintegrated.do"> <label for="username">Username:</label> <input type="text" name="username" value="${loginform.username}" class="datavalue"/><br/> <label for="password">Password:</label> <input type="text" name="password" value="" class="datavalue"/><br/> <input type="submit" name="loginEvent" value="Log In" class="strutsCommand"/> </html:form> <p><em>Username is "guest", password is "pass".</em></p> </c:if> <%-- "Logged In" subview --%> <c:if test='${not empty USER}'> <h3>User Information</h3> <html:form method="post" styleClass="strutsCommand" action="/loginintegrated.do"> <label>Current user:</label> <div class="datavalue">${USER}</div><br/> <input type="submit" name="logoutEvent" value="Log Out" class="strutsCommand"/><br/> </html:form> </c:if> </comp:component> }}} == 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: {{{ <%@ page contentType="text/html;charset=UTF-8" language="java" %> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"; %> <%@ taglib uri="http://struts.apache.org/tags-html"; prefix="html" %> <%@ taglib uri="http://struts.apache.org/tags-comp"; prefix="comp" %> <html> <body> <p>This paragraph is defined directly in the parent page and should precede the content of login control.</p> <%-- The login component, notice that DIV has the same ID as the component's name --%> <div id="Login"> <c:import url="/loginintegrated.do" /> </div> <p>This paragraph is defined directly in the parent page and should follow the content of login control.</p> </body> </html> }}} == 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!
