Portlet Development III

1
Portlet Development III
The ActionPortlet Model Tags, Beans, and Events
Jason Novotny novotny_at_aei.mpg.de Michael Russell
russell_at_aei.mpg.de Oliver Wehrens
wehrens_at_aei.mpg.de

Albert Einstein Institute
2
Critique of Portlet Model

• In complex portlet development navigation between
  various views and events can be difficult to
  manage
• Developers must still write lots of tedious
  CSS/HTML to create presentations.
• Lots of portlet actions can lead to
  actionPerformed methods with large amounts of
  branching logic

public void actionPerformed(ActionEvent event)
String actionName event.getAction().getName()
if (actionName.equals(doThis)
doThis() else if (actionName.equals(doTha
t)) doThat() else if
3
The ActionPortlet

• ActionPortlet acts as an intelligent dispatcher
  that hides branching logic from a portlet
  developer
• A subclass of ActionPortlet makes use of the
  dispatching mechanisms and defines the action and
  view methods to invoke for a particuar event
• ActionPortlet provides setNextState() method that
  is used to specify the next display state that
  should be presented after an action method. Also
  setNextTitle and setNextError are provided.
• ActionPortlet provides default actionPerformed
  and doXXX methods so normally these methods need
  not be defined in the ActionPortlet subclass
• Specify default pages in init method of portlet
  DEFAULT_VIEW_PAGE, DEFAULT_EDIT_PAGE, etc.

4
Example Portlet
public class ExamplePortlet extends ActionPortlet
public void init(PortletConfig config)
throws UnavailableException
super.init(config) public void
initConcrete(PortletSettings settings) throws
UnavailableException super.initConcrete(
settings) DEFAULT_VIEW_PAGE
example/view.jsp" public void
doStuff(FormEvent event) throws PortletException
setNextState(event.getPortletRequest()
, DEFAULT_VIEW_PAGE)
5
Action Methods

• ActionPortlet provides subclassed portlets with
  FormEvent object that acts as decorator for
  ActionEvent to provide form-based visual
  components

public interface FormEvent extends ActionEvent
public FileInputBean getFileInputBean(String
beanId) throws IOException public
ErrorFrameBean getErrorFrameBean(String beanId)
public CheckBoxBean getCheckBoxBean(String
beanId) public TextFieldBean
getTextFieldBean(String beanId) public
HiddenFieldBean getHiddenFieldBean(String
beanId) public PasswordBean
getPasswordBean(String beanId) public
TextAreaBean getTextAreaBean(String beanId)
public TextBean getTextBean(String beanId)
6
Visual Beans

• Instead of using HTML in Portlet java code,
  visual beans provide wrappers around CSS/HTML
  that allows portlet developers to modify or
  create presentation elements
• Standard HTML elements are wrapped as beans
• CheckBoxBean. ListBoxBean, TableBean,
  HiddenFieldBean, TextFieldBean, PasswordBean.
  etc.
• Beans are identified by tags, called beanId
  which acts a label.
• Beans are created at every request and are
  updated after request has been generated and made
  available to portlet action methods
• Every visual bean has a corresponding UI tag that
  may be used in JSP pages to produce presentation
  output

7
UI Tag Library

• Action model provides value-added tag library to
  make creating presentations more like component
  based design like Swing.
• Tags that wish to be accessed by a portlet must
  declare a beanId

ltuiformgt ltuipanelgt ltuiframegt
ltuitablerowgt ltuitablecell
width"100"gt ltuitext
key"LOGIN_NAME"/gt
lt/uitablecellgt lt/uitablerowgt
lt/uiframegt lt/uipanelgt lt/uiformgt
8
UI Tag Usage

• Any JSP that wishes to use the UI tag library
  must include the following boilerplate JSP
• This instructs the page to include the Portlet
  and UI tag libraries

lt_at_ taglib uri"/portletUI" prefix"ui" gt lt_at_
taglib uri"/portletAPI" prefix"portletAPI"
gt ltportletAPIinit/gt
9
UI Tag Attributes

• Most presentation beans/tags subclass from
  BaseComponentBean and BaseComponentTag which
  provides following fields
• beanId - name of the presentation tag/bean
• name - name as used in HTML elements
• value - value as used in HTML elements
• key - a key that represents a localized
  properties file key
• width - width of the component
• font - font to be used
• cssStyle - the CSS style
• Tag attributes can also be passed in as request
  time values
• ltuitext valuelt myFavoriteFruit gt/gt

10
Localized Messages

• In general any text displayed in a portlet should
  be localized
• Use the TextTag!
• ltuitext key"LOGIN"/gt
• The key attribute specifies the key used in the
  Portlet.properties_ltcountrygt file found in
  WEB-INF/classes
• All presentation tags that display text include
  key attribute
• ActionSubmitTag for displaying buttons

11
Creating Actions

• Action presentation elements can trigger portlet
  events
• ActionLink -- creates a hyperlink with a
  specified action
• ActionSubmitButton -- creates a button with a
  specified action
• Form-- provides action attribute to trigger an
  action from a form submission
• Action elements can include nested ActionParam
  elements for associating additional name/value
  parameters to an action

12
Creating Actions (cont.)

• Creating an actionlink with actionparams
• ltuiactionlink actiondoSomething" valueClick
  Me"gt
• ltuiactionparam namecolor valuered/gt
• ltuiactionparam namefruit valueapple/gt
• lt/uiactionlinkgt
• Creating a default form
• ltuiform actiondoActiongt
• ltuitextfield beanIdfruit size15
  valueapple/gt
• lt/uiformgt
• Creating a form with buttons
• ltuiformgt
• ltuiactionsubmit actiondoAction valueClick
  Me/gt
• ltuiactionsubmit actiondoAnotherAction
  valueNo, me/gt
• lt/uiformgt

13
Container Tags and Beans

• Several beans/tags act as containers for other
  beans/tags
• A ltuipanelgt tag contains nested ltuiframegt or
  ltuitablegt tags to produce stylized nested tables
  
• A ltuitablegt or ltuiframegt tag is composed of
  nested ltuitablerowgt tags which contain nested
  ltuitablecellgt tags to produce stylized tables
• A ltuiformgt tag is a container for all tags
  included within it.
• A ltuilistboxgt tag can contain nested
  ltuilistboxitemgt tags
• Action tags are containers for ltuiactionparamgt
  tags to specify additional action parameters.

14
Conclusion

• ActionPortlet model is the GridSphere
  recommended approach for building complex
  portlets
• Tags and Beans provide value-added functionality
• Default navigation methods take care of
  forwarding to the appropriate page, error
  handling and setting portlet title.
• The UI tag library provides a toolbox of reusable
  presentation components
• UI tag library frees developers from working with
  HTML/CSS
• Future goal is to integrate JavaScript/DHTML into
  tags for increased interactivity
• Please contact us with comments, questions,
  suggestions on improving the model!