Short Portlet Programming Guide in P-Grade (Gridsphere)

environmentG. Hermann

Content

• Main ideas

• Execution model

• Representation

• Part I Java – JSP collaboration

• Part II Definition of Portlets by portlet.xml and layout.xml

• Tomcat directory hierarchy

Main ideas

• Layout design and business logic are separated

• Response WEB pages are generated with the help of run time compiled and linked java code.

• Even little parts of WEB pages can be handled independently (portlet concept)

Warning !

• We restrict ourselves to the Portlet implementation of the Gridsphere

• Focus on the class ActionPortletTasks:– Defines “states” described by Java Servlet

Pages (Jsp)– Defines callback routines called

• before HTML response generation (view)• after user action (update)

Execution model - possible ways

HTTML response generation

First request from client

init(PotletConfig) Y(ActionFormEvent)

X(RenderFormEvent)

Next requests from client

Execution model-regime modify

HTTML response generation

First request from client

init(PotletConfig) Y(ActionFormEvent)

X(RenderFormEvent)

Next requests from client

Execution model-regime show

HTTML response generation

First request from client

init(PotletConfig)

X(RenderFormEvent)

Next requests from client

Representation I• java code (Action Portlet)

defines the callback routines and the current (and next) state made intuitive to the client by defining the selection of the proper Jsp page in that state. The java code is responsible for the whole business logic.

• Java Servlet Page (JSP) (file: xx.jsp) Composes the frame of the layout and defines communication interface between the client and java code in a given state.

• The UI Tag Library defines the layout and the passive –data- interface between java code and JSP. The Java representation of the UI Tag Library follows the Bean concept. The JSP representation of UI Tag Library is XML.

• “portlet.xml” defines the portlet and references the java code• “layout.xml” defines the menu hierarchy haw the callable portlets

should appear. (layout.xml is GridSphere specific!)

Representation II

HTTML response generation

First request from client

init(PotletConfig) Y(ActionFormEvent)

X(RenderFormEvent)

Next requests from client

class Any extends ActionPortlet

Ani.jsp

UI Tag Library objects

Remarks(1) UI TAG LIBRARY

• The UI Tag Library is not discussed in detailed in the subsequent example.

• The Java side usage of it is self explaining by the Bean paradigm.

• For the XML usage of it in the JSP file consult the document:http://www.gridsphere.org/gridsphere/docs/TagGuide/TagGuide.htm

• What you must know is that the interface variables are identified by associated Strings

Remarks(2) State Transitions

Please note that the event handling interrupt routines of the Java Class ActionPortlet may terminate with the state transition instruction setNextState(PortletReqest,String), where the String parameter may refer either

– a name of a routine, or– a JSP. The action defined in that JSP defines the next

state.

Remarks(3) other state subtilities

• The String “DEFAULT_HELP_PAGE” is used to define a JSP when the client hits the “?” icon on the portlet

• The String “DEFAULT_EDIT_PAGE” is used to define a JSP when client hits the “pen” edit icon.

Remarks (4) Programing style

• The JSP pages may contain direct java code fragments among UI tags and forms.However you are emphatically asked to avoid them: The overview of the program logic can be lost easily if the program code is fragmented, and the JSP is not used as its designated: for gathering and rendering of client data.

Part I: Life Cycle of a Portlet by an example

The simple Portlet “EnterName” redisplays a single string entered by the client.

EnterName.java and the corresponding EnterName.jsp files

First Request arrives from the client

HTTML response generation

First request from client

Init(PotletConfig) Y(ActionFormEvent)

X(RenderFormEvent)

Next requests from client

The routine init will be activated

Java – Jsp connections-1DEFAULT_VIEW_PAGE determinesthat before the elaboration of the first response the given rendering routinewill be called.

First Rendering

HTTML response generation

First request from client

Init(PotletConfig) Y(ActionFormEvent)

X(RenderFormEvent)

Next requests from client

Variables need to show to the client are prepared

Java – Jsp connections-2The jsp is referenced by the java code.

After the running of the routine the HTML generation defined by the Jsp will be performed

Java – Jsp connections-3

The parameter referenced by the handle “nameSessionHandle” does not exist, therefore the bean object referenced “nameOld” – wich will be created upon the first reference –receives the value “not defined”.

Java – Jsp connections-4

The bean referenced as“nameOld” will be used to display the value known by the system before the user interaction.

Java – Jsp connections-5

The jsp page will generate the HTML response

HTML generated by the JSP as it appears for the Client

The Jsp page will generate the HTML code in the response for the selected frame

Java – Jsp connections-6 The internally generated bean objects are used to exchange data between Jsp defined HTML code and Java routines

Java – Jsp connections-7

The user hitting the button labeled as “Update” generates a Request activating the routine updateName

Java – Jsp connections-8

Example: The Client fills the text field as “newValue”, and hits the Button “Update”

Repeated request arrives

HTTML response generation

First request from client

Init(PotletConfig) Y(ActionFormEvent)

X(RenderFormEvent)

Next requests from client

The prescribed ActionFormEvent handler will be activated.

Java – Jsp connections-9In the action event handler the value defined by the client and stored in a bean referenced as “nameNew” will be read

Java – Jsp connections-10

The text value will be forwarded to the subsequent rendering routine via the handle “nameSessionHandle”

Java – jsp connections

As a last step the routine triggers the rendering event

Repeated Rendering

HTTML response generation

First request from client

Init(PotletConfig) Y(ActionFormEvent)

X(RenderFormEvent)

Next requests from client

Java – Jsp connections-11

As the value associated by “nameSessionHandle” is not emptythe bean referenced as “nameOld”will receive this value

HTML generated by the JSP as it appears for the Client after repeated Rendering

The bean referenced “nameOld” now has the value “newValue”

Summary of all external Java- Jsp connections

Part II Definition of a Portlet

• A new portlet prepared by the java and JSP files must have an entry in the file “portlet.xml” and it

• must be referenced in the file “layout.xml”,

• must define an interpreter java class path,

• And a title label

portlet.xmlThe new potrlet Portlet name will

be referenced in file layout.xml

Text in the title of the portlet

Path of the java class controlling the portlet

The layout.xml

• Must define the menu hierarchy

• Define the appropriate labels for the user navigation

• Reference the used portlets

layout.xml

Portlet as a submenu

item

Display name of a group of a submenu

Display name of of a submenu

item

Referencing the name of the potled defined in portlet.xml

Referencing the web application

Summary of connectons: layout.xml, portlet.xml and HTML image

webapps/

…/

…/

jsp/

…/

WEB-INF/

…/

portal30/…/

…/hello/…/

…/

enterName.jsp

…jsp

…jsp

lib/

classes/

…/

portlet.xml

layout.xml

hu/

sztaki/

lpds/

pgportal/

portlets/

hello/EnterName.class

Tomcat dictionary

The jar files encountered here must correspond to the import references defined in

EnterName.java