Intro to j Sps and Serv Lets

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Saturday, October 11, 2008

Xabriel J. Collazo MojicaTA for ICOM 5016

University of Puerto Rico at Mayagez

Introduction to JavaServer

Pages & Servlets

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TheoryMVC Pattern

JSPs & Servlets denedThings you need to know

Project Hierarchy

Practice Java on a JSP

Scriplets, EL & Standard ActionsYour projects rst phaseQuick workshop

Agenda

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MVC Pattern in a Web context

From [2]

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MVC Pattern in Java EE context

From [1]

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Servlets are Java programming language classesthat dynamically process requests and constructresponses.

JSP pages are text-based documents thatexecute as servlets but allow a more naturalapproach to creating static content.

Suns definitions

From [1]

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Youll need to learn a few things:HTML : Hyper Text Markup Language

Markup language for Web pagesCSS : Cascade Style Sheets

Used to describe the presentation of a documentwritten in a markup language

Servlet API & JSP APIUsed to make al l the nif ty dynamic tricks.

SQL : Structured Query LanguageThe core of your project.

Things you need to know

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http://en.wikipedia.org/wiki/SQLhttp://tomcat.apache.org/tomcat-5.5-doc/servletapi/index.htmlhttp://tomcat.apache.org/tomcat-5.5-doc/jspapi/http://en.wikipedia.org/wiki/SQLhttp://en.wikipedia.org/wiki/SQLhttp://tomcat.apache.org/tomcat-5.5-doc/jspapi/http://tomcat.apache.org/tomcat-5.5-doc/jspapi/http://tomcat.apache.org/tomcat-5.5-doc/servletapi/index.htmlhttp://tomcat.apache.org/tomcat-5.5-doc/servletapi/index.htmlhttp://en.wikipedia.org/wiki/Cascading_Style_Sheetshttp://en.wikipedia.org/wiki/Cascading_Style_Sheetshttp://en.wikipedia.org/wiki/HTMLhttp://en.wikipedia.org/wiki/HTML


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and perhaps:A little JavaScript

A scripting language. For dynamic stu f on the clientside; its what Gmail and Facebook rely on.

EL & JSTLNew way to do Java without Java inside JSPs.

Things you may need to know

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http://java.sun.com/products/jsp/jstl/reference/docs/index.htmlhttp://java.sun.com/products/jsp/jstl/reference/docs/index.htmlhttp://en.wikipedia.org/wiki/Unified_Expression_Languagehttp://en.wikipedia.org/wiki/Unified_Expression_Languagehttp://en.wikipedia.org/wiki/Javascripthttp://en.wikipedia.org/wiki/Javascript


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Eclipse / Sun Project Hierarchy

Sun

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Project > Properties > Java Build Path >Libraries

For example, if it is theServlet API we want toadd, we click on AddExternal JARs andbrowse to the jar le.

Note that in the case of Tomcat, the jar we wantis at: /tomcat_root/common/lib/servlet-api.jar

How to add aReference inEclipse

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You can add Java to a JSP in three di f erent ways:As a Directive

As a Scriplet

As an Expression

ava on a JSP

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Imports a package to use it inside the JSP.

Embeds another JSP (or HTML [or anything!]) intothe current JSP. Great to avoid duplication code!

Relevant JSP directives

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Actual code from MY class project ( Fall 2007)

ava inside JSPs?

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So the guys behind all this stu f , after quite awhile, realized that is bad practice to embed Javain JSPs.

What did they do? They invented anotherpseudo-language and a big library:

Standard ActionsEL = Expression LanguageStandard Tag Library : JSTL

What should we use then?

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EL : A simpler way to invoke Java codeExample:

email: ${applicationScope.mail}

Standard Actions : Cute ways to write Java (I haveno better denition!)

Example:

EL & Standard Actions

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JSTL : Everyday stu f (like loops & conditionals)Example:

${person.name} ${person.age} ${person.height}

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Quick comparison: Scriplets vs.

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Quick comparison: EL vs. SA

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The course professors dont care how you do itas long as it uses Java, JSPs and Servlets.

So, use whatever you want: scriplets, EL,anything.

But be advised!

I recommend you use EL, JSTL and/or StandardActions!In that order of preference!

What about YOUR project

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Nothing of this applies to the rst phase of yourproject! Lucky you!

All you need to do for now is some dummy JSPpages with servlets that redirect to more dummy

JSPs.

Anyway

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protected void doGet(HttpServletRequestrequest, HttpServletResponse response)throws ServletException, IOException {

String addr = aJSPAddress" ;RequestDispatcher dispatcher =

request.getRequestDispatcher(addr);

dispatcher.forward(request,response);

}

Your Servlets (for now :)

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Heres where you actually do some work

WhatYouNeedToDoForFirstPhase

Workshop

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[1] The Java EE 5 Tutorial. http://java.sun.com/ javaee/5/docs/tutorial/doc/index.html .

[2] BetterExplained MVC tutorial. http://

betterexplained.com/articles/intermediate-rails-understanding-models-views-and-controllers/

Book: Head First Servlets & JSP. OReilly. Some year :)

All other links direct to the Wikipedia articles on therespective subjects.

References & Further Info

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http://betterexplained.com/articles/intermediate-rails-understanding-models-views-and-controllers/http://betterexplained.com/articles/intermediate-rails-understanding-models-views-and-controllers/http://betterexplained.com/articles/intermediate-rails-understanding-models-views-and-controllers/http://betterexplained.com/articles/intermediate-rails-understanding-models-views-and-controllers/http://betterexplained.com/articles/intermediate-rails-understanding-models-views-and-controllers/http://betterexplained.com/articles/intermediate-rails-understanding-models-views-and-controllers/http://betterexplained.com/articles/intermediate-rails-understanding-models-views-and-controllers/http://java.sun.com/javaee/5/docs/tutorial/doc/index.htmlhttp://java.sun.com/javaee/5/docs/tutorial/doc/index.htmlhttp://java.sun.com/javaee/5/docs/tutorial/doc/index.htmlhttp://java.sun.com/javaee/5/docs/tutorial/doc/index.html

Intro to j Sps and Serv Lets

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