COMP9321 Web Application Engineeringcs9321/17s2/lectures/lec03/Lec-03.pdf · COMP9321 Web Application Engineering Semester 2, 2017 Dr.Amin Beheshti Service Oriented Computing Group,

COMP9321 Web Application EngineeringSemester 2, 2017

Dr. Amin BeheshtiService Oriented Computing Group, CSE, UNSW Australia

Week 3

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http://webapps.cse.unsw.edu.au/webcms2/course/index.php?cid=2465

Review: Static vs. Dynamic Web Page

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A static web page is delivered to the user exactly as stored, in contrast to dynamic web pages which are generated by a web application, and on demand!

web page whose construction is controlled by an application server processing server-side scripts.

software framework that provides both facilities to create web applications and a server environment to run them.

is-a

is-a

Java application servers

e.g.

It's core set of API and features are defined by Java EE.

The Web modules include Java Servlets and JavaServer Pages (JSP).

http://docs.oracle.com/javaee/6/tutorial/doc/

Review: Java Servlets

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http://java.sun.com/products/servlet/index.jsphttp://docs.oracle.com/javaee/6/tutorial/doc/bnafd.html

JavaServer Pages (JSP) Technology

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JavaServer Pages (JSP) Technology

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• JavaServer Pages (JSP) technology allows you to easily create web content that has both static and dynamic components.

• JSP technology makes available all the dynamic capabilities ofJava Servlet technology; but provides a more natural approachto creating static content.

• JSP is similar to PHP, but it uses the Java programminglanguage.

• To deploy and run JavaServer Pages, a compatible web serverwith a servlet container, such as Apache Tomcat, is required.

Main Features of JSP technology

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• A language for developing JSP pages, which are text-baseddocuments that describe how to process a request andconstruct a response;

• An Expression Language (EL) for accessing server-sideobjects;

• Mechanisms for defining extensions to the JSP language;

JSP Page

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A JSP page is a text document that contains two types of text:

• Static data:o which can be expressed in any text-based format (such as HTML, SVG,

WML, and XML);• JSP elements:

o which construct dynamic content;o The recommended file extension for the source file of a JSP page is .jsp.o The recommended extension for the source file of a fragment of a JSP

page is .jspf.

Encapsulates a portion of JSP code in an object that can be invoked as many times as needed.

JSP Page

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Kinds of tags:• <%= … %> is used for expressions.

• e.g. <%= request.getParameter ("email") %>

• <%! … %> is used for declarations.• e.g. <%! String name, email; %>

• <% … %> is used for straight Java code.• e.g. <% if (x > 5) { … %>

• <%@ … %> is used to include another file (e.g.HTML file) or a package (e.g. java.sql.*).• e.g. <%@ page contentType="text/html; charset=UTF-8" %>• e.g. <%@ taglib uri="http://java.sun.com/jsp/jstl/core " prefix="c" %>

JSP Example

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The Request:

<html><body><h3>Enter your name and email address: </h3><form method="get" action="hello.jsp">

<p><input type="text" name="name" value="" size="20"/> Name </p><p><input type="text" name="email" value="" size="20"/> Email </p><p><input type="submit" name="Send" value="Send"/> </p>

</form></body>

</html>

JSP Example

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JSP File: hello.jsp

<%@ page contentType="text/html; charset=UTF-8" %><%@ taglib uri="http://java.sun.com/jsp/jstl/core " …%><html><body>

<%! String name, email; %><jsp:useBean id="hello" scope="session" class="greetings.HelloBean" /><jsp:setProperty name="hello" property="name"

value='<%= request.getParameter ("name") %>‘ /><jsp:setProperty name="hello" property="email"

value=‘<%= request.getParameter ("email") %>‘ /><%

name = hello.getName();email = hello.getEmail();out.println ("<h3>Hello, your name is " + name);out.println (" and your email address is " + email + ".</h3>");

%></body></html>

JSP Example

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JSP File:






%></body></html>

<%@page ... %>• page directive.• sets the content type returned by the page.

JSP Example

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JSP File:






%></body></html>

<%@taglib ... %>• Tag library directives.• import custom tag libraries.JavaServer Pages Standard Tag Library (JSTL):

• JSTL extends the JSP specification by adding a tag library of JSP tags for common tasks, such as conditional execution, loops, and database access.

JSP Example

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JSP File:






%></body></html>

<jsp:useBean …>• is a standard element that creates an object containing a collection of

locales and initializes an identifier that points to that object.

• is used to locate or instantiate a bean class.

• Google(“what is a bean class?”)

JSP Example

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JSP File:






%></body></html>

JSP Example

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JSP File:






%></body></html>

<jsp:setProperty …>• is a standard element that sets the value of an object property.

JSP Example

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JSP File:






%></body></html>

JSP Example

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JSP File:






%></body></html>

Some reserved words (JSP Objects):• request – an instance of HttpServletRequest.• response – an instance of HttpServletResponse.• out – a PrintWriter object for the response.• session – the HttpSession object associated with the session.• application – an instance of ServletContext

Some reserved words (JSP Objects):• request – an instance of HttpServletRequest.• response – an instance of HttpServletResponse.• out – a PrintWriter object for the response.• session – the HttpSession object associated with the session.• application – an instance of ServletContext

JSP Example

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The Bean:

public class HelloBean{

private String name = "";private String email = "";

public String getName() {return name;}public String getEmail() {return email;}

public void setName (String n) {name = n;}public void setEmail (String e) {email = e;}

} // HelloBean

• Each Java server page is associated with a Java bean.• These are Java programs and reside on the server.

o All variables have accessor (get) and mutator (set) methods.

JSP

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Let us Revisit the WelcomeServlet

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Here is equivalent in JSP (welcome.jsp)

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JSP Basics

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JSP Page

JSP Elements

Template Text (HTML bits…)

ScriptingElements

DirectiveElements

ActionElements

Traditional

Modern EL Scripting${…}

ScriptletExpressionDeclarationComments

PageIncludeTaglib

custom

Standard

<abc:mytag>

<jsp:useBean><jsp:getProperty><jsp:setProperty><jsp:include><jsp:forward><jsp:param>

JSP Basics

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JSP Page

JSP Elements


ScriptingElements

DirectiveElements

ActionElements

Traditional



PageIncludeTaglib

custom

Standard

<abc:mytag>


JSP Elements: JSP directives

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JSP Elements: JSP directives

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http://www.tutorialspoint.com/jsp/taglib_directive.htm

<%@ taglib uri="http://www.example.com/custlib" prefix="mytag" %><html><body><mytag:hello/></body></html>

JSP Basics

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JSP Page

JSP Elements


ScriptingElements

DirectiveElements

ActionElements

Traditional



PageIncludeTaglib

custom

Standard

<abc:mytag>


JSP Elements: JSP Scripting (expression)

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JSP Elements: Using the implicit objects

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request: the HttpServletRequest object response: the HttpServletResponse object session: the HttpSession object associated with the request out: the Writer object config: the ServletCong object application: the ServletContext object

Example:<html><body>

<h2>JSP expressions</h2><ul>

<li>Current time is: <%= new java.util.Date() %><li>Server Info: <%= application.getServerInfo() %> <li>Servlet Init Info: <%= config.getInitParameter("WebMaster") %><li>This Session ID: <%= session.getId() %><li>The value of <code>TestParam</code> is:<%= request.getParameter("TestParam") %>

</ul></body></html>

JSP Elements: JSP Scripting (scriptlet)

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• JSP scriptlet, are inserted verbatim into the translated servlet code.

• The scriptlet can contain any number of language statements, variable or method declarations, or expressions that are valid in the page scripting language.

• Within a scriptlet, you can do any of the following:• Declare variables or methods to use later in the JSP page.• Write expressions valid in the page scripting language.• Use any of the implicit objects or any object declared with a <jsp:useBean> element.• Write any other statement valid in the scripting language used in the JSP page.

Remember that JSP expressions contain `(string) values', but JSP scriptlets contain `Java statements'.


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Example:

<HTML><BODY>

<%// This scriptlet declares and initializes "date"java.util.Date date = new java.util.Date();

%>Hello! The time is:<%

out.println( date );out.println( "<BR>Your machine's address is: " );out.println( request.getRemoteHost());

%></BODY></HTML>


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The following three examples, generate the same output …


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Example, setting the background of a page

(CoreServlet p.334)


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You can also use the scriptlet to conditionally generate HTML.

JSP Elements: JSP Scripting (comment)

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Attributes in a JSP

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(HeadFirst) p.309

Recall from last week. Request attributes and RequestDispatcher:• We use request attributes when we want some other component of the application take

over all or part of your request….

JSP Basics

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JSP Page

JSP Elements


ScriptingElements

DirectiveElements

ActionElements

Traditional



PageIncludeTaglib

custom

Standard

<abc:mytag>


JSP Elements: JSP Actions

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(HeadFirst) p.309

JSP Elements: JSP Actions (include)

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jsp:include vs. include directive

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(CoreServlet p.380)

JSP Elements: JSP Actions (forward)

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JSP Elements: JSP Actions (useBean)

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Sharing Beans: using scope attribute


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Sharing Beans: using scope attribute

JSP Basics

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JSP Page

JSP Elements


ScriptingElements

DirectiveElements

ActionElements

Traditional



PageIncludeTaglib

custom

Standard

<abc:mytag>


Expression Language (EL) in JSP

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Towards Script-less JSP


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(HeadFIrst) p.367


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EL Basics: Accessing Scoped Variables

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EL Basics: Accessing Scoped Variables

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EL Basics: Using dot vs. Using [ ] operator

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EL Basics: EL Implicit Objects

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EL Basics: EL Operators

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Assignment 1

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Appendix

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JSP Standard Tag Library (JSTL)

AND

JSP Custom Tags


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JSTL Basics: Looping collections

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JSTL Basics: Conditional output

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JSTL Basics: Conditional output

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2- https://www.ibm.com/developerworks/library/j-jstl0318/

JSTL Basics: Using <c:set>

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Other things available in JSTL

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JSP Basics

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JSP Page

JSP Elements


ScriptingElements

DirectiveElements

ActionElements

Traditional



PageIncludeTaglib

custom

Standard

<abc:mytag>


JSP Custom Tags

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JSP Custom Tags

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http://www.tutorialspoint.com/jsp/jsp_custom_tags.htm

http://docs.oracle.com/javaee/5/tutorial/doc/bnalj.html

Example:

More Details:

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COMP9321 Web Application Engineeringcs9321/17s2/lectures/lec03/Lec-03.pdf · COMP9321 Web Application Engineering Semester 2, 2017 Dr.Amin Beheshti Service Oriented Computing Group,

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