developing web applications using java server pages (jsp) final

8/17/2019 Developing Web Applications Using Java Server Pages (JSP) Final

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Applications using Java

Server Pages (JSP)

JavaTM Education & Technology Services

Copyright© Information Technology Institute 1


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Table of Contents

•

• Chapter 2: JSP Syntax•


Copyright© Information Technology Institute http://jets.iti.gov.eg 2


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JSP Basics




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Chapter 1 Outline

What is Java Server Page (JSP)?

What is the difference between servlets and JSP?

van ages o .

How JSP look like?

How JSP works?

javax.servlet.jsp package. JspPage interface

HttpJspPage Interface



JSP Classes


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What is Java Server Page (JSP) ?

• “An extension of the servlet technology created

“ .

– Most Web pages are HTML.

–

the servlet programmer.

– No clear separation of presentation and logic.

– Little bit difficult for web programmers.




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What is the difference between servlets andJSP?

• Servlets:

– .

– Generate dynamic content. – .

• JavaServer Pages: –

they can be pure XML.

– .

– Separate static and dynamic content.




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Benefits of JSP

• Easier to author (Web-site development tools).

.

• Business and presentation logic are separated.

• mp y eve opmen w , ava eans an

custom tags.•

components.

the source file.

•JavaTM Education & Technology Services


.


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How JSP look like?

• tags stay as they are. When you need to add dynamiccontent, all you need to do is enclose your code in tags

Using JSP

Enumeration parameters = request.getParameterNames();

String param = null;

while (parameters.hasMoreElements()) {

param = (String) parameters.nextElement();

out.println(param + ":" + request.getParameter(param) +"
");}

out.close();%>




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How JSP works ?

J2EE container

1Firsttime

YesWeb

container ( page compiler )

http://host/date.jspCreate servletdate.javaNo

2

date.class

Servlet life cycle

3




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Example

public void _jspService(…..)

{

out.write("\r\n");

" ".

out.write("\r\n");

out.write("\r\n");< ou .pr n n s easy ; > ou .pr n n s easy ;

out.write("\r\n");

out.write("\r\n");

out.write("");

}




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Notes on JSP life Cycle



* Source: Core Servlets and Javaserver Pages By Marty Hall, Larry Brown ISBN 0130092290


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Why JSP developers need servlets?

1. JSP pages are translated into servlets.

. cons s s o s a c , ags, an

Java code (Servlet code).

. ome as s are e er accomp s e y serv e s

than by JSP.. .




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javax.servlet.jsp.*

•

– javax.servlet.jsp – javax.servlet.jsp.tagext custom tags - Advanced

• javax.servlet.jsp contains 2 interfaces , 2

Exceptions and 4 classes

• Interfaces :

– JspPage – HttpJspPage




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javax.servlet.jsp.* (cont’d)

• Classes: – sp ac ory

– PageContext

–

– JspWriter

•

– JspException

– Js Error.




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JspPage interface

• The JspPage is the interface that must be implementedb all JSP servlet classes.

• It contains two methods: – public void jspInit()

– ublic void s Destro

Example:


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HttpJspPage Interface

• It extends the JspPage interface.

• It has got only one method :

– public void _jspService ( HttpServletRequest

request,HttpServletResponse response ) throws

ServletException, IOException.

• It’s called by the JSP container, to generate the content

of the JSP page.

• you can't include this method in a JSP page, because



.


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JSP Classes

•

• The JspEngineInfo class• “ ”

• The JspWriter class




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1-The JspFactory Class

• n a s rac c ass a prov es me o s or o a n ngother objects needed for the JSP page processing.

• The class has the static method getDefaultFactory that

returns a JspFactory object.

• From the JspFactory object, a PageContext and aJspEngineInfo object can be obtained using

:

– public abstract JspEngineInfo getEngineInfo( )

– pu c a s rac age on ex ge age on ex erv erequestingServlet, ServletRequest request,ServletResponse response, String errorPageURL,



, ,


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The JspFactory Class (cont.)

• The followin code is art of the s Servicemethod that is generated by the JSP container:

_

PageContext pageContext = null;

_jspxFactory =JspFactory.getDefaultFactory();

pageContext = _jspxFactory.getPageContext ( this,

request,response, ,true, 8192,true);




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2-The JspEngineInfo Class

–

that provides information on the JSPcontainer.

– It has only one method,

getSpecificationVersion, returns the JSPcontainer's version number.




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3-The PageContext Class

– PageContext represents a class that provides

methods that are im lementation-de endent.

– ,

the _ jspService method of a JSP servlet

class, a PageContext object is obtained bycalling the getPageContext method of the

JspFactory class.




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The PageContext Class (cont.)

– The PageContext class provides methods thatare used to create other objects.

• getOut method returns a JspWriter object that is

used to send strings to the web browser.

• ge eques , re urns a erv e eques o ec .

• getResponse, returns a ServletResponse object., .

• getServletContext, returns a ServletContext object.

• etSession returns an Htt Session ob ect.




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4-The JspWriter Class

• The JspWriter class is derived from the

ava.io.Writer class and re resents a Writer that

you can use to write to the client browser.

• Of its many methods, the most important are the

print and println methods.




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Implicit Objects of PageContext class

• . . .

• response javax.servlet.http.HttpServletResponse• . . .

• session javax.servlet.http.HttpSession

. .

• config javax.servlet.ServletConfig




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Review

•

file• If the code written in the JSP a e was onl :




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Strategies for invoking dynamic code

. a ava co e rec y cr p e s Simple

. ,

only the Java code needed to invoke the utility classes.

3. Develop separate utility classes structured as beans.

4. MVC architecture. A servlet respond to original request,

look up data, and store results in beans, forward to a

1. Use the JSP expression language.Complex



2. Use custom tags.


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Strategies for invoking dynamic code (cont’)

• Why limiting the amount of Java code in JSP

a es ?

– Development. – Compilation.

– Debugging.

– Division of labor. – Testing.

– Reuse.




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Assignments

• .

• Make an html page that redirect a request to anJSP




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JSP Syntax




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Chapter 2 Outline

JSP tags :

Scripting elements

Action elements

Converting into XML syntax




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JSP Syntax

• JSP contains 2 main things :

– ags e emen s : ma e up e syn ax an

semantics of JSP. – Tem late Data : an thin else not understood b

the JSP container

• example :HTML tags

• JSP tags are :

– Directive elements

– cr p ng e emen s

– Action elements




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JSP tags

JSP tags

ScriptingDirective Action

page Scriptlets

include Declarations

taglib Expressions




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1-Directive Elements

• They are messages to the JSP containercontaining information on how the JSP containermust translate a JSP page into a corresponding

servlet.•

not a code.

• – Page directives

– Include directives

– Tag library directives (used with custom tags )




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1-Directive Elements (cont’d)

•

– • Exam le

–

–


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1 Directive Elements (cont d)a-Page Directive Attributes

Atribute Value Type Default

import Fully qualified class name None

contentType MIME type, character set"text/html;charset=ISO-

8859-1”session Boolean “true”

buffer Buffer size in Kb or false 8192

autoFlush Boolean "true”

errorPage URL None

isErrorPage Boolean "false”

isThreadSafe Boolean "true”

extends Class name None

lan ua e Scri tin lan ua e name " ava"





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•

– –

–

– –

• It’s not allowed to repeat assigned attributes

excep or mpor a r u e





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Notes on import attribute

• 1st and 2nd strategy for invoking dynamic code.

• Utility classes should always be in packages and the JSP

page should use the import attribute.

• , . . ,

javax.servlet.*, javax.servlet.jsp.*, javax.servlet.http.*.

• The onl a e attribute that is allowed to a ear multi le

times.

• The utility classes should be placed in /WEB-NF/classes/

• Note:





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1 Directive Elements (cont d)b-The Include Directive

• It enables JSP page authors to include the

contents of other files in the current P a e.

• We can include static page like html or anotherJSP a e.

• Include Syntax:

–

• Example:

–


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2-Scripting Elements

•

pages.• 1st and 2nd strate for invokin d namic code.

• There are three types:

– Scri tlets

– Declarations

– Expressions



2-Scripting Elements (cont’d)


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2 Scripting Elements (cont d)a-Scriptlets

• Inserted into the servlet’s _jspService method

• Syntax

• xamp e:





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2 Scripting Elements (cont d)b-Declarations

• t s use to ec are met o s or var a es.• Inserted into the body of the servlet class, outside

any ex s ng me o s.

• Can not access the implict objects of _jspService

• Syntax:

• Examples:

return Calendar.getInstance().getTime().toString();

>





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2 Scripting Elements (cont d)c-Expressions

• It’s used to evaluate expressions and print them

to the user.

• It’s used instead of out.println()

• Syntax:

< = >

• Example:

The same result of :

out.print( java.util.Calendar.getInstance().getTime() );



A i t


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Assignment

• Write a utility class that generates a random

.

• Invoke methods of this utility class from jsp page.




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3-Standard Action Elements

They consists of :

• jsp:forward• s : aram

• jsp:plugin

• jsp:params• jsp:fallback

• jsp:useBean

• jsp:setProperty

• jsp:getProperty



3-Standard Action Elements(cont’)


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( )Include, forward and param

• They got the same effect of RequestDispatcher

include and forward

• Syntax:=" “

( )*

( )*





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Notes on jsp:include• The included pages can be

- es, p a n ex es, pages, erv e s

- With JSP pages and servlets, only the output of the pageis included not the actual code.

• Do not use complete HTML documents for the included

pages.• The included page uses the same request object as the

originally requested page and sees the same request

• The main page can add to or replace the request

parameters using jsp:param.





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Notes on jsp:forward• Using jsp:forward obtain the complete output from the

.

• The main page must not have any output.• The main a e can add to or re lace the re uest

parameters using jsp:param.



jsp incl de s incl de di ecti e


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jsp:include vs. include directive

•

sp: nc u e page= ur nc u e e= ur

• nc u e e ou pu o

a page at request time

main page before that

main page is translatedinto a servlet.

• No change needed in

the main page when the

• The main page must be

updated whenever any of

the included a es.

•The included pages

change.

• The included code can

cannot use any JSP

constructs that affect the

main page as a whole.

such as field definitions

and content-type settings

that affect the main page



as a whole.

Assignment


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Assignment

• Use both jsp:include and include directive to

difference.



3-Standard Action Elements(cont.)


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( )Plugin, Fallback and params

• Sun developed a browser plug-in for Netscape andInternet Explorer that lets you use the Java 2 platform in

a var e y o rowser vers ons.

• In some browsers, the normal APPLET tag will not workwith the lu -in. Instead use OBJECT ta for Internet

Explorer and EMBED tag for Netscape.

• The is used to generate HTML or < > ags a ns ruc e rowser o own oa

the Java Plugin software, if required, and initiate the

execution of the Java applet specified.• Note: The applet .class files must not be placed in WEB-

INF/classes, as the browser, not the server, uses them.



3-Standard Action Elements(cont.)


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Plugin, Fallback and params


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useBean, setProperty and getProperty

•

– Will be described in details in the next chapter



Comment tag


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Comment tag

• HTML comments

< -- -->

• JSP comment



Assignment


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Assignment

• Use to embed Applet in your jsppage.





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•

– The content of the JSP page can be validated againsta set of descriptions.

– The JSP page can be manipulated using an XML

tool.

–

representation by applying an XML transformation



Converting into XML syntax (cont’d)


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Converting into XML syntax (cont d)

• Syntax –

– < sp: ec ara on> ec ara on co e < sp: ec ara on>

– scriptlet code – < > < >

• Examples:< s :directive. a e attr=“value” />

String s; s =request.getParameter("user");

…….



Converting into XML syntax (cont’d)


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Converting into XML syntax (cont d)

• Notes on XML Syntax: – XML element names can contain colons, XML-

compa e vers on o a s an ar e emen s

starts with the jsp prefix (or namespace).

– XML tags are case sensitive.

– XML tags must be explicitly closed.

– To get ' within an attribute value, use \‘.

To get ", use \“; to get \, use \\; to get %>, use %\>;



, .


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JSP and Java Beans



Chapter 3 Outline


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Chapter 3 Outline

What is a Bean?

.

How to use a request parameter to feed the value of a



What is a Bean?


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What is a Bean?

• A bean is a java class with certain rules defined

by the JavaBeans specification.

• Beans extend no particular class and use no

particular interface.

• The 3rd strategy for invoking dynamic code.



Why beans?


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Why beans?

• Why we should use beans in JSP ?

– .

– No Java syntax, instead XML-compatible tags.

– Clear separation of roles.

– Simpler object sharing.

– Convenient correspondence between requestparame ers an o ec proper es.



Java Beans Rules


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Java Beans Rules

• A bean class must have a default constructor(which will be called when JSP elements or

servlets create beans).

• A bean class should have no public instance

variables.

• Persistent values (properties) should be

accessed through methods called getXxx and

setXxx.



Or isXxx and setXxx for bolean properties.

Java Beans Rules (cont’)


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Java Beans Rules (cont )

• Example:- If our Book bean class has a lon instance variable

isbn and a boolean borrowed.

- Then your bean class should have the following

standard JSP actions:

long getIsbn ()

void setIsbn (long isbn)

boolean isBorrowed ()

void setBorrowed (boolean borrowed)



Java Beans Rules (cont’)


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Java Beans Rules (cont )

• Notes on Bean classes :

– Place all your beans in packages.

– Install them in the normal Java code directories:

WEB-INF/classes/ for individual classes and

WEB-INF/lib for JAR files.



Tag Structure


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Tag Structure

• < sp:use ean attr ute= va ue + >• Main attributes :

– id

– class – , , ,

• Example:

“ " " "

class=" com.mybeans.MyFirstBean"/>

• This element can either build a new bean or



.

Tag Structure (cont’)


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Tag Structure (cont )

• You must use the fully qualified class name forthe class attribute regardless of whether you use

to import packages.



& TagsSt t


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Structure

• Accessing Properties in a bean through : – jsp:getProperty

– jsp:setProperty

Syntax:

• This element reads and outputs the value of a

bean property.

• Reading a property means calling its getXxx



method.

& TagsSt t ( t’)


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Structure (cont’)

< =" "

property=“propertyName" value="value"/>

• This element modifies a bean property (i.e.,

.



& TagsStructure (cont’)


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Structure (cont )

• JSP expression could be used to call a methodon the object with the variable specified by the id

attribute.


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Structure (cont’)

• JSP scriptlet could be used to explicitly callmethods on the bean object.

• It is not advisable but can be useful in settin thevalue conditionally or calling methods other than

get Xxx or set Xxx on the object.



Example


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a p e

.

public class MyFirstBean {

public String getFirstName()

{

return firstName;

}public void setFirstName(String name)

{

= ;} }



property called firstName.

Example (cont.)


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p ( )

< = “ ”

class=“com.mybeans.MyFirstBean” />

The First Name is < s : etPro ertname=“myBean” property=“firstName” />



Example (cont.)


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p ( )

• Note You can access the bean methods usingscripting tags

< r ng name = ;

myBean.setFirstName (name);

The First Name is

• Note: Whenever possible, avoid mixing the XML-

compatible jsp:useBean tags with JSP scripting elements



con a n ng exp c ava co e.

How to use a request parameter to feed thevalue of a bean variable ?


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value of a bean variable ?

Consider this case:


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value of a bean variable ? (cont )

• JSP offers a better solution:


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value of a bean variable ? (cont )

• If the request parameter name and the bean

could be omittedExam le:

If the request parameter has the name isbn



Scope of the Bean


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p

•

• request• sess on

• application



Scope of the Bean (cont’)


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p ( )

1. page:

– The default value.

– The bean is bound to a local variable (accessible by.

– The bean object is placed in the PageContext object

for the duration of the current request. – The code can access it by calling getAttribute on the

predefined pageContext variable of the page.

– e ean s no s are an us a new ean w ecreated for each request.





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p ( )

2. request:

– .

– The bean object is placed in the HttpServletRequestobject for the duration of the current request.

– The servlet code can access it by calling getAttribute

on the request variable. – o e a wo pages or a page an a serv e

share request objects jsp:include, jsp:forward or the

include or forward methods of RequestDispatcher is

used.





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3. session:

– The bean is bound to a local variable.

– The bean object will be stored in the HttpSessiono ec assoc a e w e curren reques .

– The servlet code can access it by calling getAttribute

on the session variable.





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4. application:

– e ean s oun o a oca var a e.

– The bean object will be stored in the ServletContextavailable throu h the redefined a lication variable

or by a call to getServletContext.

– The ServletContext is shared by all servlets and JSPpages n e e app ca on.

– Values in the ServletContext can be retrieved with the




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Assignment


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• Write a jsp page that populates a Java bean with

jsp page or servlet that displays the data.




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MVC Frameworks



Chapter 4 Outline


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MVC Design Pattern.

MVC Frameworks.

mp emen ng w eques spa c er.



MVC Design Pattern


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• Model-View-Controller (MVC) is an architecturaldesign pattern used to build complex computer

applications.

• It aims to separate data (model) and usern er ace v ew .

• The MVC architecture divides applications intoree ayers :

• Model: The data and business logic

• Controller: The flow control



Why MVC?


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• Why MVC?

.

• Business logic and presentation are separated.• Flexibilit : chan e in one la er does not affect

the other.

2. Ease of maintenance.

. u y, , …



MVC Frameworks


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• The 4th strategy for invoking dynamic code.

• The ori inal re uest is handled b a servlet.

• The servlet invokes the business-logic and data-access

code and creates beans to represent the results , decidesw c page presen ose resu s an orwar s e

request to it.

• This servlet is the Controller .

• The beans representing the results are the Model.

• The jsp that presents the results are the View.



• The most popular MVC framework is Apache Struts.

MVC Frameworks (cont’)


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Controller 1-request

Client 3

2

browser

View

(JSP)5-response 4



Steps of Implementing MVC


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1. Define beans to represent the data.

. .

3. The servlet invokes business logic or data-access code

to obtain the results. The results are placed in the

beans (Populate the beans).

4. Store the bean in the request, session, or servlet

.

5. Forward the request to a JSP page (using forward

method of RequestDispatcher)

6. Extract the data from the beans. The JSP page

accesses beans with jsp:useBean and jsp:getProperty



.

Notes on the Steps of Implementing MVC


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• The Java beans must have a default constructor since aservlet or other Java routine (never a JSP page) will

.

• A controller servlet handles the initial re uest it can read

request parameters and request headers.

• The controller servlet can also use the populateBean

method of Jakarta Commons BeanUtils component to

parameters.



Notes on the Steps of Implementing MVC (cont’)


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• Jakarta Commons BeanUtils component performs thereflection and the type conversion.

• You can download this component fromp: commons.apac e.org componen s. m

•

– List the JAR files in your CLASSPATH for development.

– Put the JAR files in the WEB-INF/lib directory of your Web

, .

• To share JAR files across Web applications, put JAR

files in /common/lib.



Example on using BeanUtils component


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import org.apache.commons.beanutils.BeanUtils;

public class MyRequestServlet extends HttpServlet

public void doGet(HttpServletRequest request,

HttpServletResponse response) throws ServletException,

PrintWriter out=response.getWriter();

MyBean bean=new MyBean();ry

BeanUtils.populate (bean, request.getParameterMap());

}catch(Exception e)

{

e.printStackTrace();



} }



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• The Servlet can then call some business logic code,invoke an Enterprise JavaBeans component, or query a

a a ase o e erm ne e resu s an n e va ue

object beans.

• A servlet can store data for JSP pages in three main

places: in the HttpServletRequest, in the HttpSession,an n e erv e on ex .





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ean ec ean = new ean ec ... ;

request.setAttribute ("key", bean );

BeanObject bean = new BeanObject (...);

getServletContext().setAttribute("key", bean );



sp:use ean = ey ype= my ac age. ean ec

scope= “application” />



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• You can place your jsp pages under the WEB-INF

directory to prevent clients from accessing them directly

.

• Using forward method of RequestDispatcher, makes the

client sees the URL of the original servlet, not the URL of

the final JSP page.

• If the destination page uses relative URLs for images or

style sheets, it needs to make them relative to the servlet

URL or the server root, not to the destination page’s

actual location.

" ”



. . - .

TYPE="text/css">

Project


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• After the user correctly log in to the Application,a specified home page is displayed according to

the priviliges of the user.

• Only the managers can add, edit or delete

another employee.

• Implement the MVC architecture and avoid usingdirect java code in the jsp pages as much as you

can.



References & Recommended Reading


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• Core Servlets and JSP.

• ava or e e w erv e s, , an .

• Sun presentations.• Oracle presentations.

• SCJWD study guide.

developing web applications using java server pages (jsp) final

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