Advanced Web Systems 2- Portal and Portlet A. Venturini
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Advanced Web Systems 2- Portal and Portlet
A. Venturini
Contents
What is a portlet?
Why portlets?
Portal and portlet architecture
Portlet vs. Sevlet
Portlet and Web application frameworks
Portlet modes and Windows states
Portlet features
Portlet APIs
Most of the slides taken from a presentation of:
Sang Shin, [email protected], www.javapassion.com
What is a Portlet?
Java technology based web component
Managed by a portal container
Generates a piece of markup called “fragment”
Adheres to certain rules such as no <html>
tags, for instance
Fragment generated by a Portlet aggregates
with that from other Portlets to form a portal
page
Fragment generated by a Portlet may
vary from one user to another depending
on the user configuration
Portlet Specifications
JavaTM Portlet Specification
First version: JSR 168
Second version: JSR 286
http://www.jcp.org/en/jsr/detail?id=286
Standard specificatitons defined by the major
portal vendors (ibm, sun, bea, …) for portlet
technologies
What does JSR-168 define?
Portlet API
Portlet Requests
Preferences
User information
Security
Deployment packaging
Portlet Container
Extension of servlet container
Contract between component and
container
What are out-of-scope of JSR 168?
These are out of scope of JSR 168: these are
handled by Portal server
Aggregation
Layout management
Page personalization and configuration
engines
Portal administration and configuration
What happens when clicking on a link?
when clicking on a portlet link, typically the
content of that portlet should change.
The other portlet, should keep their status
(typically not change there view, but sometimes
they do!)
Portal and Portlet Interaction
User Portal Portlet
container
Portlets
A B C
render
render
render
processAction
A
B C
A’
B’ C
Action on B Do action on B
Render A
Render B
Render C
These requests
may be done in
parallel
Scope of the Portlet specification Outside of the scope of the Portlet specification
Why Portlet? (Why can't we use Servlet?)
Why Portlets?
Servlet architecture does not define the
Desktop metaphor where markup aggregation
can occur
Servlet architecture does not define the
possible states and transitions of an included
Servlet or JSP
Servlet architecture does not define how the
state of one Servlet or JSP affects the display
of the other included Servlets or JSPs
Why Portlets?
Servlet architecture does not define a
personalization interface nor the idea
of persisting the personalization
information
Servlet architecture does not define
URL-rewriting functions to allow the
creation of links and actions targeted
to a specific form within the fragment
of a page (Portlet markup fragment)
Servlet architecture does not support
caching scheme of fragments
JSR 168 Value Proposition: Portability of Portlet Apps
JSR 168
Compliant
Portals
Write Once
Deploy to Many
Po
rtle
t In
terf
ace
Portal Architecture
With JSR 168 Support
Portal
User Agent Browser, Phone, PDA
Portlet Container
Portlet Portlet
Portlet
Network Aggregation
Personalization Security
Portal/Portlet Architecture
User
Configuration/
Personalization
Engine
Persistent Data Store
Portlet Dispatcher
Window Config Security
Portlet
Enterprise
Information
Systems
Remote
Execution
module
Portlet
Aggregation
Engine
Portlet
Portal server
Portal/Portal Server
A “specialized” web application that provides
value-added services such as
Personalization
Single Sign-On
Content aggregation from various sources
Secure search facilities
Localization of content
A Portal “page” represents a complete markup
document consisting of several Portlet
components
Portal server is the platform
Portlet Container
Portlets are deployed in a Portlet container
such that container can
Provides runtime environment for Portlets
Manage life cycle of Portlets
Provide persistent storage for storing Portlet
preferences
Cache the portlets
Receive requests from the portal to execute
requests on the portlet
Not responsible for contents aggregation
Similarity with Servlet
Both are Java technology based web components
Life-cycle is managed by a specialized container
Servlet by servlet container
Portlet by portlet container
Both generate dynamic content
Both interact with web client via a request/response
paradigm
Common Foundation between Servlets and Portlets
Deployment model
Classloading
Packaging and deployment
Lifecycle management
Session management
Request dispatching
Differences from Servlet
Portlets only generate markup fragments, not
complete documents
Portlets are not directly bound to a URL
Web clients interact with portlets through a portal
system
Portlets have a more refined request handling
action requests and render requests
Portlets have predefined states
portlet modes and window states
Portlets can exist many times in a portal page
Extra Features of Portlets
Portlets have means for accessing and
storing persistent configuration and
customization data
Portlets have access to user profile
information
Portlets have URL rewriting functions for
creating hyperlinks within their content
allow portal server agnostic creation of links and
actions in page fragments
Portlets can store transient data in the portlet
session in two different scopes
application-wide scope
the portlet private scope
Servlet Features Forbidden to Portlets
Setting the character set encoding of the response
Setting HTTP headers on the response
Accessing the URL of the client request to the portal
(!)
Servlet Features that are leveraged by Portlets
Portlets can leverage servlets, JSPs and JSP tag-
libraries for generating content
Content should be markup fragment
A portlet can call servlets and JSPs using a
request dispatcher
Integration between the two
Attributes set in the portlet request are available
in the included servlet request
Attributes set in the portlet session are accessible
from the servlet session and vice versa
Portlet and the included servlet or JSP share the
same output stream
Portlet and Web App. Frameworks
Portlet and Web App. Frameworks
Struts/JSF
Struts/JSF are built over Servlets
Struts/JSF is available for Portlets
APIs exposed to Struts/JSF developers
remain the same
Struts/JSF developers must be aware of the
markup fragment he has to produce
The markup fragment must follow the
rules
Generate Portlet URL
The Spring Framework
Spring is a Lightweight Application Framework
Where Struts, WebWork and others can be
considered Web frameworks, Spring addresses
all tiers of an application
Spring provides the plumbing so that you don’t
have to!
Spring Framework History
Started 2002/2003 by Rod Johnson and Juergen Holler
Started as a framework developed around Rod Johnson’s book Expert One-on-One J2EE Design and Development
Spring 1.0 Released March 2004
2004/2005 Spring is emerging as a leading full-stack Java/J2EE application framework
Why Spring Portlet MVC ?
Can be used in any JSR-168 compliant portlet
container
It promotes best practices such as coding to
interfaces and dependency injection
It supports multiple view technologies:
e.g. JSP, Velocity and FreeMarker.
It mirrors the Spring Web MVC framework. Easy to
convert.
It supports the action phase and render phase of a
portlet request – not hidden from the developer.
Spring provides support for all the application
layers!
Portlet Modes & Windows State
Portlet Modes
Indicates function that a portlet performs
Execute different tasks and generate different
content based on the function they perform
Portals must support three modes
VIEW
Portlet renders markup fragment in this mode
EDIT
Used to change per-user settings to customize
rendering
HELP
Used to display help information
Portlet Modes (Contd.)
Portals might support other custom modes
ABOUT
CONFIG
EDIT_DEFAULTS
PREVIEW
Portals might support other vendor specific
modes
Windows State
Is an indicator of the amount of portal page space that
will be assigned to the content generated by a portlet
Provided by portlet container
Three states
NORMAL
MAXIMIZED
MINIMIZED
Custom states are possible
Portlet Features
Portlet Persistence
Portlets can store persistent data for a given
user in a PortletPreferences object
Preferences are read-write in the action phase
(processAction()) and read-only in render
phase
Usually user preferences are modified in EDIT
mode
User Profile Attributes
Can store information about user that can be
used to personalize content for that user
User profile information is represented as a
USER_INFO structure which is then mapped to
the real information in datastore
Portlet defines the attributes it wants to access
in the deployment descriptor
Portal context
Can provide information on
Portal vendor
Version
Used by portlets to find out more information
about additional extensions supported by
Portal
Security
Authentication is left to the underlying servlet
container
Authorization
Follows J2EE ‘roles’ model
Supports programmatic role checking
Session Management
Facade on top of the HttpSession
Two scopes: APPLICATION & PORTLET
PORTLET is a convenience namespacing
It’s common for portlets to appear more than
once in a page (i.e.: EU-News, US-News)
Servlets, JSPs and Portlets within a Portlet
Application share the same session
Session creation event notification is supported
Portlet Request Dispatcher
Portlets can include Servlets, JSPs and static
content during a render request
Similar to Servlet’s RequestDispatcher
Localization
Portlets can be localized by using resource
bundles
Resource bundles are specified in deployment
descriptor
Portlet can access resource bundle via
PortletContext.getResourceBundle() API
Caching
Expiration based caching
Declarative caching
Specify <expiration-cache> element in
deployment descriptor for the portlet
Programmatic caching
Modify EXPIRATION_CACHE property of
render response
Portlet URL
Portlets are always accessed through a Portal
Portlets do not have a direct URL mapping
Portlet URLs allow Portlets to create URLs that
target to themselves (through the Portal end-
point)
Portlet API's
Java Portlet API
javax.portlet.Portlet
javax.portlet.GenericPortlet
javax.portlet.ActionRequest
javax.portlet.ActionResponse
javax.portlet.RenderRequest
javax.portlet.RenderResponse
Portlet Life Cycle
Handle requests
Destroyed by container
Initialized by
container
init()
processAction()
destroy()
Notifies initialization of portlet by container.
processAction() notifies the Portlet about user's request for action.
render()
render() notifies the Portlet to generate the markup fragment
destroy() notifies the destruction of portlet by container. Should free up resources in this method.
Portlet Interface
1 public interface Portlet {
2 public void init(PortletConfig config) throws PortletException; 3 4 // Action Request: Invoked only when the URL is an action targeted 5 // to the portlet, it does not produce output 6 public void processAction( ActionRequest request, 7 ActionResponse response) 8 throws PortletException, IOException;
9 // Render Request: Invoked on every request to the portal, it 10 // produces output to create the portal page 11 public void render(RenderRequest request, 12 RenderResponse response) 13 throws PortletException, IOException;
14 public void destroy(); 15 }
GenericPortlet class
Implements Portlet interface
Render()--like service() in servlets, calls
specified render methods based on Portlet
mode
doView() for View mode
doEdit() for Edit mode
doHelp() for Help mode
Is extended by portlet developers
Override render methods as necessary
javax.portlet.GenericPortlet
protected void doView(...)
protected void doEdit(...)
protected void doHelp(...)
protected void processAction(...)
DoView()
doView() doEdit() doHelp()
HTML
Portlet
Render()
DoEdit()
Portlet
Edit Form
Render() doView() doEdit() doHelp() HTML
ProcessAction()
Portlet container
processAction() store() doView()
Other Interfaces/Classes
PortletConfig, PortletContext,
PortletSession
PortletPreferences interface
WindowState (MINIMIZED,
NORMAL & MAXIMIZED)
PortletMode (VIEW, EDIT & HELP)
PortletURL
PortletRequestDispatcher
Portlet Tag Library
PortletPreferences
Persistent read/write Portlet configuration
getValues(), setValues() to access
PortletPreferences
May modify attributes and store() in persistence
during processAction()
Normally, portlet preferences are per portlet/per
user
Persistency is managed by the portlet-container
Default values are defined in the portlet.xml
deployment descriptor
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