Comparative Display Technologies in Sakai Aaron Zeckoski azeckoskigmail

What do we want out of a display technology? • Easy to use for

What technologies work • Virtually any Java related display technology can work in Sakai

What games are there in town? http: //java. sun. com/products/servlet/ http: //jakarta. apache. org/velocity/

Java Servlets Intro • modules of Java code that run in a server app

Code Snippet package org. java. helloworld; import java. io. *; import javax. servlet. http.

Java Servlets + • Tried and tested technology (1997) • Runs on the server

Java Servlets • • • Invented in 1997 for goodness sake! HTML is placed

Java Servlets Final • Why would you want to write pure Servlets any more

Velocity Templates Intro • Java based template engine • Uses “references” to place dynamic

Code Snippet <HTML> <HEAD><title>Velocity Sample</title></HEAD> <BODY> <h 1>Hello $user. name</h 1> <table> #foreach( $item

Velocity Templates + • Uses “references” to place dynamic content in html template pages

Velocity Templates • The current Velocity implementation in Sakai is a custom and out

Velocity Templates Final • Go for technologies that provide better separation between Code and

Java Server Pages Intro • Dynamic Java web content scripting language – Very similar

Code Snippet <HTML> <HEAD><title>JSP Sample</title></HEAD> <BODY> <h 1>Hello <%= user. get. Name() %></h 1>

Java Server Pages + • Easy to develop in and work with • Can

Java Server Pages • Mixes code and HTML together – Poor separation of code

Java Server Pages Final • JSP support in Sakai is not great yet •

Java Server Faces Intro JSF • A Java based set of APIs for managing

Code Snippet JSF <%@ taglib uri="http: //java. sun. com/jsf/html" prefix="h" %> <%@ taglib uri="http:

Java Server Faces + JSF • The second most used display technology in Sakai

Java Server Faces - JSF • Pretty heavyweight and has problems in the current

Java Server Faces Final JSF • Most new apps in Sakai are written in

Reasonable Server Faces • Spring based web programming framework • Uses pure XHTML templates,

Code Snippet <html> <head><title>RSF sample</title></head> <body> <h 1>Hello <span rsf: id=“user-name”>User Name</span></h 1> Today

Reasonable Server Faces + • Uses pure XHTML templates – Provides clean separation of

Reasonable Server Faces • Greater separation of UI and code can require more files

Reasonable Server Faces Final • The only really good separation of UI design and

Summary • • • JSF • • No plain Servlets Velocity discouraged JSP ok

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Comparative Display Technologies in Sakai • Aaron Zeckoski • azeckoski@gmail. com Sakai Montreal CRIM Workshop Creative Commons Attribution. Non. Commercial-Share. Alike 2. 5 License Sakai Programmer's Café

What do we want out of a display technology? • Easy to use for the developer • Good separation of Code and UI – i. e. easy to use for the UI designer • Good integration with Sakai – Portal, widgets, tools, etc… 2

What technologies work • Virtually any Java related display technology can work in Sakai • There are some caveats – Sakai uses a special Servlet to handle redirects and processing of HTTP request variables – Portal and widget interaction have to be developed for each technology • Bottom line: You are better off sticking with the ones that currently work 3

What games are there in town? http: //java. sun. com/products/servlet/ http: //jakarta. apache. org/velocity/ http: //java. sun. com/products/jsp/ JSF http: //java. sun. com/javaee/javaserverfaces/ http: //www 2. caret. cam. ac. uk/rsfwiki/ But there a few things to consider… 4

Java Servlets Intro • modules of Java code that run in a server app to answer client requests • HTML is hardcoded in the Java class – It can be pulled from external files though • Most more advanced technologies are built on Servlets • Sakai uses Servlet API 2. 4 URL: http: //en. wikipedia. org/wiki/Java_Servlet 5

Code Snippet package org. java. helloworld; import java. io. *; import javax. servlet. http. *; public class Hello. World extends Http. Servlet { public void do. Get(Http. Servlet. Request request, Http. Servlet. Response response) throws Servlet. Exception, IOException { Print. Writer out = response. get. Writer(); out. println("Hello World"); } } URL: http: //www. apl. jhu. edu/~hall/java/Servlet-Tutorial-First-Servlets. html 6

Java Servlets + • Tried and tested technology (1997) • Runs on the server instead of on the client like an applet • Pure Java code • Session tracking via Http. Servlet • Works fine in Sakai – Café Servlet Hello World sample code 7

Java Servlets • • • Invented in 1997 for goodness sake! HTML is placed in the Java class Impossible for UI designers to work with Poor separation of UI and Code Development this way is painful and slow compared to more modern methods 8

Java Servlets Final • Why would you want to write pure Servlets any more considering the many better options out there? • You are going to use Servlets anyway but at least use something along with it • Bottom line: Don’t use this unless you just want to put an existing Servlet app into Sakai 9

Velocity Templates Intro • Java based template engine • Uses “references” to place dynamic content in html pages with # or $ vars – Somewhat similar to PHP or JSP • Meant to allow UI designers to work alongside programmers • Apache project URL: http: //jakarta. apache. org/velocity/ 10

Code Snippet <HTML> <HEAD><title>Velocity Sample</title></HEAD> <BODY> <h 1>Hello $user. name</h 1> <table> #foreach( $item in $items ) #if ( $item. Check($item) ) <tr> <td> $item. value </td> </tr> #end </table> </BODY> </HTML> 11

Velocity Templates + • Uses “references” to place dynamic content in html template pages – Somewhat similar to PHP or JSP • Most used display technology in Sakai – Integration with Sakai is good • Ok separation of UI and Code • Decent docs and community 12

Velocity Templates • The current Velocity implementation in Sakai is a custom and out of date version • Integration with Sakai is OK but not really being worked on much anymore • New development in Velocity is discouraged by the community • Mostly carried over from CHEF 13

Velocity Templates Final • Go for technologies that provide better separation between Code and UI • Bottom line: You are better off not using this, only use this if you have existing apps and cannot rewrite them 14

Java Server Pages Intro • Dynamic Java web content scripting language – Very similar to PHP • JSP pages are compiled into Servlets when accessed • Pages are a mixture of HTML, taglib tags, and Code URL: http: //java. sun. com/products/jsp/ 15

Code Snippet <HTML> <HEAD><title>JSP Sample</title></HEAD> <BODY> <h 1>Hello <%= user. get. Name() %></h 1> Today is <%= new Date() %><br/> <ul> <% for (int i=0; i<items. size(); i++) { %> <li><%= ((Item)items. get(i)). get. Value() %></li> <% } %> </ul> </BODY> </HTML> 16

Java Server Pages + • Easy to develop in and work with • Can be changed without restarting • Works fairly well in Sakai – JSP support is available via a cool Servlet by Andrew Thornton (Cambridge) – Used in Rwiki (sorta), XML version • Well tested technology with large community • Excellent docs and many books 17

Java Server Pages • Mixes code and HTML together – Poor separation of code and UI design • Compiled when accessed – This can cause a noticeable delay when accessing a page for the first time • Integration with Sakai is poor • Has many of the same weaknesses that other scripting languages have 18

Java Server Pages Final • JSP support in Sakai is not great yet • It is difficult for UI designers • Bottom line: Use this if you have existing JSP code, but go for options that provider better separation between UI and Code for new projects 19

Java Server Faces Intro JSF • A Java based set of APIs for managing state, handling events, and defining navigation • Mostly builds on JSP – Though it can be used without JSPs • Includes a custom set of tag libraries • Includes error handling, input validation, and internationalization support URL: http: //java. sun. com/javaee/javaserverfaces/ 20

Code Snippet JSF <%@ taglib uri="http: //java. sun. com/jsf/html" prefix="h" %> <%@ taglib uri="http: //java. sun. com/jsf/core" prefix="f" %> <html> <head><title>JSF sample</title></head> <body> <f: view> <h 1><h: output. Text value=“Hello #{user. name}"/></h 1> <h: data. Table id=“items" value="#{items. Bean. items}" var=“item"> <h: column> <h: output. Text value="#{item. value}" /> </h: column> </h: data. Table> </f: view> </body> </html> 21

Java Server Faces + JSF • The second most used display technology in Sakai (after Velocity) – Used for the portal and a small number of apps (Gradebook, Assignments, etc…) • Integrates well with Sakai – better than any of the other current solutions (for now) • My. Faces and Oracle ADF Faces • Pretty good docs and books 22

Java Server Faces - JSF • Pretty heavyweight and has problems in the current version – These might be fixed in the upcoming version • • • Poor separation of UI design and code High learning curve Difficult to use and not very flexible Poor AJAX/Javascript integration Does not work with browser navigation 23

Java Server Faces Final JSF • Most new apps in Sakai are written in this but it is recognized as having many weaknesses • High learning curve and difficulty of use means slow development • Bottom line: Don’t use this unless you really have to, even if you have existing code 24

Reasonable Server Faces • Spring based web programming framework • Uses pure XHTML templates, clean separation of UI and Code • Lightweight and pure bean programming • Works well with AJAX and Javascript URL: http: //jakarta. apache. org/velocity/ 25

Code Snippet <html> <head><title>RSF sample</title></head> <body> <h 1>Hello <span rsf: id=“user-name”>User Name</span></h 1> Today is <span rsf: id=“current-date”>1/1/2006</span><br/> <table> <tr rsf: id=“items: ”> <td rsf: id=“item-value”>item value here</td> </tr> </table> </body> </html> 26

Reasonable Server Faces + • Uses pure XHTML templates – Provides clean separation of UI and Code • Respects the HTTP request cycle – Back button works! • Works well with AJAX and Javascript • Sakai integration and features are improving rapidly • Good docs and code samples available on the RSF Wiki 27

Reasonable Server Faces • Greater separation of UI and code can require more files and lines of code – This is true of other solutions as well • Not used in Sakai core yet but is fully functional in it and integrates somewhat – Some code in Sakai Contrib (rsf gallery) • Small user community • Still in development (also a positive) 28

Reasonable Server Faces Final • The only really good separation of UI design and Code available • Community support is growing and Sakai integration improving • Bottom line: Use of this is recommended for new Sakai apps 29

Summary • • • JSF • • No plain Servlets Velocity discouraged JSP ok for small stuff JSF is just bad RSF recommended 30