Introduction to Jakarta Struts Framework

1
Introduction to Jakarta Struts Framework

• Try
• NCCU Computer Center
• Mar 20,2002

2
The Evolution of Server Side Web Ap Developement

• CGI(or ISAPI)
• Servlet
• JSP
• JSPBean (Model 1)
• JSPBeanXML techs
• Model 2 (MVC)
• Model 2X(MVC with XML techs)

3
What is MVC

• The Model View Controller is a technique used to
  separate Business logic/state (the Model) from
  User Interface (the View) and program
  progression/flow (the Control).
• This pattern is very useful when it comes to
  modern web development
• The majority of modern, high usage websites are
  dynamically driven.
• People well skilled at presentation (HTML
  writers) seldom know how to develop back-end
  solutions and visa versa.
• Separating business rules from presentation is
  good no matter what environment you develop in be
  it web or desktop.

???? Craig W. Tataryn ,Introduction to MVC and
the Jakarta Struts Framework
4
(No Transcript)
5
Benefits of MVC

• Promotes Modularity
• I18n
• Abstraction
• Allows application to be defined in a flow-chart,
  use-case or activity diagram which is more
  easily transferred to implementation.

???? Craig W. Tataryn ,Introduction to MVC and
the Jakarta Struts Framework
6
The Struts Framework overview

• Struts is an open source MVC framework developed
  by the Apache Jakarta project group.
• Struts allows JSP/Servlet writers the ability to
  fashion their web applications using the MVC
  design pattern.
• By designing your web application using Struts
  you allow
• Architect the ability to design using the MVC
  pattern
• Developer to exploit the Struts framework when
  building the app.
• Web designer can learn how to program in MVC.

???? http//jakarta.apache.org/struts/
7
The Struts Framework overview(2)

• Struts takes much difficult work out of
  developing an MVC based web app.
• The Struts framework provides a collection of
  canned objects which can facilitate fundamental
  aspects of MVC, while allowing you to extend
  further as need suites

8
Components of Struts Framework

• Model
• Business Logic Bean(or session bean)?StateBean(or
  entity bean)?ActionForm?
• View
• A Set of Tag library.
• Language Resource File
• Controller
• ActionServlet( controlled by struct-configs.xml)
• ActionClasses
• Utility Classes

9
Components of Struts Framework(2)
???? http//www-106.ibm.com/developerworks/library
/j-struts/?n-j-2151
10
How Struts works
???? http//www-106.ibm.com/developerworks/library
/j-struts/?n-j-2151
11
View

• The view in Struts is represented by JSP pages.
• Minimize the occurance of scriptlets in your page
• Use the tag-library provided by Struts to control
  the presenatational logic.

12
ViewI18n

• The ability to maintain a web app in several
  different languages
• Based on the language setup on the client side,
  the web app will automatically switch.
• This is achieve in Struts through Java Resource
  Bundles
• Instead of having to make a ResourceBundle class
  for each language supported by your web app,
  resource bundles can be described as language
  resource files

13
Demo
Traditional Chinese
English
14
ViewI18n(2)

• Language Resource
• FileName Conventions
• (ResourceName)_(ISO-LanguageCode)_(ISO-ConturyCod
  e).properties
• Register the Resource Name in web.xml.
• In order for web developers to get at the string
  resources we use a special Struts tag called
  ltbeanmessage/gt

15
ViewExample

• Login.jsp
• ApplicationResources_en_US.properties
• ApplicationResources_zh_TW.properties

16
Model

• ResultBean,hold information needed to generate
  the result page.
• FromBean(extend ActionForm ),hold the data passed
  by user either by POST or Query String.
• Business Logic Bean.
• EJB ?JMS or other components we impl at business
  logic layer before.

17
ModelActionForm

• JSP pages acting as the view for this LogonForm
  are automatically updated by Struts with the
  current values of the UserName and Password
  properties.
• If the user changes the properties via the JSP
  page, the LogonForm will automatically be updated
  by Struts
• Before an ActionForm object is passed to a
  controller for processing, a validate method
  can be implemented on the form which allows the
  form to belay processing until the user fixes
  invalid input

18
ModelExample

• LoginForm.java
• tw.edu.nccu.user.TeacherData

19
Control

• The controller is the switch board of MVC.
• It directs the user to the appropriate views by
  providing the view with the correct model
• The task of directing users to appropriate views
  is called mapping in struts.
• The Struts framework provides a base object
  called org.apache.struts.action.ActionServlet.
• The ActionServlet class uses a configuration file
  called struts-config.xml to read mapping data
  called action mappings
• The ActionServlet class reads the incoming URI
  and tries to match the URI against a set of
  action mappings to see if it can find a
  controller class which would be willing to handle
  the request

20
Controller (2)
http//TeacherStudata/login.action
Server configured to pass .action extensions to
org.apache.struts.action.ActionServlet via a
web.xml configuration file
ActionServlet object inspects the URI and tries
to match it against an ActionMapping located in
the struts-config.xml file.
Instance of appropriate Action class is found and
its perform() method is called
Action object handles the request and returns
control to a view based where the user is
within the flow of the application
21
ControlExample

• tw.edu.nccu.teacherstudata.actions.LoginAction
• Struts-config.xml
• LoginAction.java

22
Problems with Struts

• Does not work on JDK1.4.0
• Steep learning curve.
• Problems on old Application Servers(include
  Tomcat3.2.1 ?Weblogic 5.1).
• The only output document is HTML,it didnt
  support the XSL transform technology.(Unless we
  modify the source code)

23
Model 2X

• Model2X
• Conceived by Julien Mercay and Gilbert Bouzeid on
  Feb 1,2002.
• Replace the JSPTagLib with XMLXSLT at
  presentation layer.
• Using XSL Servlet as the Document Factory.
• Support pipe-line processing while generating the
  target document.

24
(No Transcript)
25
(No Transcript)
26
Resource

• Struts homepage
• http//jakarta.apache.org/struts/
• Suns Servlet Specification
• http//java.sun.com/products/servlet/download.html
  specs
• Suns JSP Specification
• http//java.sun.com/products/jsp/download.html
• Blue Stones Struts Tutorial
• http//developer.bluestone.com/scripts/SaISAPI.dll
  /Gallery.class/demos/trailMaps/index.jsp
• My Struts page
• http//java.cc.nccu.edu.tw/struts/