JSR 168 vs IBM Portlet API

Similarities

The following concepts are very similar in JSR 168 and the IBM Portlet API.

Feature	Similarities	Differences
Portlet modes	Both support the basic portlet modes: Edit, Help, and View.	The config mode is optional in the JSR 168. The other optional JSR 168 modes (About, Edit_defaults, Preview, Print) are not supported by the IBM Portlet API.
Window states	These window states are supported: Maximized, Normal, and Minimized.	The Solo window state is only supported by the IBM Portlet API.
Portlet lifecycle	The lifecycle life cycle is the same: init, process requests, destroy.	none
Request processing	Request processing is divided into an action phase for processing user actions and a render phase for producing the markup.	none
URL encoding	Both support creating URLs pointing to the portlet or to a resource.	none
Include servlets/JSPs	Servlets and JSPs can be included in the portlet.	none
Portlet session	Portlets can store transient information that should span requests in a session.	none
Portlet application packaging	Both package portlet applications as WAR files with an additional deployment descriptor called portlet.xml.	The portlet.xml format differs.
Expiration-based caching	The portlet can support expiration based caching.	The APIs use different mechanisms to implement this functionality. The IBM Portlet API uses a polling mechanism where the portal queries the portlet for how long the markup will be valid, whereas in the JSR 168 the portlet can attach an expiration time to each created markup. Sharing the cache entry across users is only possible in the IBM Portlet API.

Differences

The JSR 168 and the IBM Portlet API differ in the following ways.

Feature	IBM Portlet API	JSR 168
Portlet application entities	Lets you define an abstract portlet application and different instance of this portlet application as concrete portlet applications via the deployment descriptor. This allows reusing settings of the abstract portlet application and only overwriting the parts that are unique for each concrete portlet application.	The deployment descriptor follows the web.xml deployment descriptor and defines one portlet application and the portlet definitions for this application.
Portlet entity	There is one portlet object instance per portlet configuration in the Web deployment descriptor. There may be many PortletSettings objects parameterizing the same portlet object according to the Flyweight pattern, provided on a per-request basis. Changes in the PortletSettings apply to all portlet instances of this concrete portlet. The user can also have personal views of concrete portlets that are rendered using the PortletData for customization of the output.	PortletSettings and PortletData are merged into one object called PortletPreferences.
Request/Response objects	The request/response object that the portlet receives in the render call is the same as the one received in the action call.	In the JSR 168 these are two different objects.

Exclusive to JSR 168
These items are only available in the JSR 168.

Feature	Description
Render parameters	Render parameters allow the portlet to store its navigational state. Render parameters stay the same for subsequent render requests and only change when the portlet receives a new action. This enables bookmarkability and solves the browser back button problem.
Global HttpSession scope	Portlets can store data not only with the visibility of the portlet, but also with the visibility of the whole Web application.
Redirect	Portlets can redirect to other Web resources in the action phase.

Exclusive to the IBM Portlet API
The following concepts are only available in the IBM Portlet API.

Feature	Description
Eventing	Events can be sent between portlets.
Additional lifecycle listeners	Lifecycle listeners besides action and render, (such as begin page) are not available in the first version of the JSR 168.
Portlet menus	Lets the portlet contribute content to a menu bar to facilitate navigation through portal pages.
Invalidation based caching	Lets the portlet explicitly invalidate cached content.

Example Portlets

This section shows a HelloWorld portlet implemented in each of the two APIs. The key differences are highlighted in the second portlet.

The two example portlets implement the same functions:

• Use JSPs for rendering the output
• Customize the portlet output, based on user-specific data
• Handle actions to allow the user to change these

This example shows a hello world portlet which uses personalization. It addresses the user by name, and it allows the user into edit mode to set a new user name. In the action method (called actionPerformed in the IBM Portlet API and processAction in JSR 168), the portlet persistently stores the new user name which the user enters.

 IBM Portlet API example portlet
First look at the portlet implemented using the IBM Portlet API.

public class HelloWorld extends AbstractPortlet implements ActionListener { €¦ public void doView (PortletRequest request, PortletResponse response) throws PortletException, IOException { //Get the user's name to display from persistent storage PortletData portletData = request.getData(); String stringToDisplay=(String)portletData.getAttribute("userName"); if (stringToDisplay == null) { stringToDisplay = defaultString; // set default string } // Add the display string to the portlet request to make it // accessible by the view JSP request.setAttribute("userName", stringToDisplay); // Get a context for the current session for invoking the JSP PortletContext context = getPortletConfig().getContext(); context.include(viewJSP, request, response); } public void doEdit(PortletRequest portletRequest, PortletResponse portletResponse ) throws PortletException, IOException { // Create the cancel return URI for the edit page PortletURI cancelURI = portletResponse.createReturnURI(); // Preserve the Cancel URI in the request to make it // accessible by the edit JSP portletRequest.setAttribute("cancelURI", cancelURI.toString()); // Create the save URI for the edit page PortletURI saveURI = portletResponse.createReturnURI(); // For the "Save" button the return URI must include the "Save" action // so the Action Listener for this portlet will be invoked SimpleActionHelper. addSimplePortletAction(getPortletConfig().getContext(), saveURI, "save"); // Preserve the Save URI in the request to make it accessible by // the edit JSP portletRequest.setAttribute("saveURI", saveURI.toString()); //Get the user's name to display from persistent storage String stringToDisplay = (String) portletRequest.getData().getAttribute("userName"); if (stringToDisplay == null) { stringToDisplay = defaultString; // none found, set default string } // Add the display string to the request to make it accessible by the // edit JSP as an inital value of the input field on the edit form portletRequest.setAttribute("userName", stringToDisplay); // Get a context for the current session for invoking the JSP PortletContext context = getPortletConfig().getContext(); context.include(editJSP, portletRequest, portletResponse); } public void actionPerformed(ActionEvent event) { String action = SimpleActionHelper.getActionString(getPortletConfig().getContext(), event); HelloWorld helloPortlet = (HelloWorld)event.getPortlet(); PortletLog log = helloPortlet.getPortletLog(); // If this is a save action, then see if the user specified a name if ( action!=null ) { if ( action.equals("save") ) { PortletRequest request = event.getRequest(); PortletData portData = request.getData(); String userName = request.getParameter("userName"); try { // Save the name specified by the user if ( userName != null ) { portData.setAttribute("userName", userName); portData.store(); } } catch ( AccessDeniedException ade ) { } catch ( IOException ioe ) { log.error( " Couldn't write the user date to persistence because an I/O Error occurred. " ); } } } } }

JSR example portlet
Now, look at the same portlet that has been modified to use JSR 168. The changed text is marked in bold.

public class HelloWorld extends GenericPortlet { €¦ public void doView (RenderRequest request, RenderResponse response) throws PortletException, IOException { //Get the user's name to display from persistent storage PortletPreferences portletData = request.getPreferences(); String stringToDisplay = (String) portletData.getValue("userName",defaultString); // Add the display string to the portlet request to make it // accessible by the view JSP request.setAttribute("userName", stringToDisplay); // Get a context for the current session for invoking the JSP PortletRequestDispatcher rd = getPortletContext().getRequestDispatcher(viewJSP); rd.include(request, response); } public void doEdit(RenderRequest portletRequest, RenderResponse portletResponse ) throws PortletException, IOException { // Create the cancel URI for the edit page PortletURL cancelURI = portletResponse.createActionURL(); // Preserve the Cancel URI in the request to make it // accessible by the edit JSP portletRequest.setAttribute("cancelURI", cancelURI.toString()); // Create the save URI for the edit page PortletURL saveURI = portletResponse.createActionURL(); // For the "Save" button the return URI must include the "Save" action // so the Action Listener for this portlet will be invoked saveURI.setParameter("action", "save"); // Preserve the Save URI in the request to make it accessible by // the edit JSP portletRequest.setAttribute("saveURI", saveURI.toString()); //Get the user's name to display from persistent storage String stringToDisplay = portletRequest.getPreferences().getValue("userName", defaultString); // Add the display string to the request to make it accessible by the edit JSP // as an inital value of the input field on the edit form portletRequest.setAttribute("userName", stringToDisplay); // Get a context for the current session for invoking the JSP PortletRequestDispatcher rd = getPortletContext().getRequestDispatcher(editJSP); rd.include(portletRequest, portletResponse); } public void processAction(ActionRequest request, ActionResponse response) throws PortletException, IOException { String action = request.getParameter("action"); // If this is a save action, then see if the user specified a name if ( action!=null ) { if ( action.equals("save") ) { PortletPreferences portData = request.getPreferences(); String userName = request.getParameter("userName"); // Save the name specified by the user if ( userName != null ) { portData.setAttribute("userName", userName); portData.store(); } }

The major differences to the IBM Portlet API version of the portlet are:

1. Request dispatcher usage The request dispatcher usage differs slightly between JSR 168 and the IBM Portlet API. JSR 168 uses the same mechanism to get a request dispatcher from context with the path as parameter as the servlet API.
   
2. Persistent portlet data JSR 168 persistent data, PortletPreferences, have an API similar to the JDK 1.4 Preferences and allows specifying a default value for the get methods. The code to check for a null return value and explicitly set a default value are no longer necessary . JSR 168 only allows String and String arrays as values of preferences; arbitrary objects are allowed by the IBM Portlet API.
   
3. Action handling The action handling in JSR 168 is simplified and does not need specific action objects to be created. Creating an action URL automatically triggers a call to the processAction method.