Java Server Pages JSP

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Java Server Pages (JSP)
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Generating dynamic content page

• The most common way is CGI
• Allowing web server to launch a program on the
  host machine
• perform the necessary task and to communicate the
  result back to the web server.
• Required loading/unloading of application each
  time.
• Used interpreted languages usually.
• Problem of CGI
• Multiple users generate multiple programs
• Heavy RAM/CPU requirements
• Load and Unload time substantial

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The technology we needed

• Working on any web or application server
• Separating the application logic from the
  appearance of the page
• Allowing fast development and testing
• Simplifying the process of developing interactive
  web-based applications

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Alternatives

• ASPs Active Server Pages
• Microsoft technology (proprietary)
• relies on COM architecture, bound to Windows
• PHP
• open source
• available on Windows, Linux, other platforms
• include scripting language commands (including
  range of function calls) in HTML
• good database support

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Alternatives Servlet

• Write programs in Java that inherit from
  Servlet which can communicate with the web
  server
• Extend HTTP Server,
• Full access to Java APIs
• Benefits
• Conceivably faster since is partially compiled
  and hence its easier to interpret.
• Load the JVM once (cache repeatedly loaded
  applets in memory too)
• Platform independence
• Problems (no MVC)
• no separation between content and presentation
• handle requests to database (data manipulation)
• manage the overall work (controlling)
• write output back to web client (presentation)

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HTTP Requests Response

• Client makes HTTP request
• Request is resolved to Servlet
• Container
• creates servlet
• invokes init()
• creates request and response objects
• invokes service()
• Sevlet interact with response
• Container replies to HTTP request
• Container may
• invoke destroy(), dispose servlet at anytime

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A servlet example

• public class HelloServlet extends HttpServlet
• public void doGet(HttpServletRequest request,
• HttpServletResponse response)
• response.setContentType("text/plain")
• PrintWriter out response.getWriter()
• out.println("lthtmlgt")
• out.println("Hello World!")
• out.println("ltbrgt")
• JspCalendar clock new JspCalender()
• out.println("Today is")
• out.println("ltulgt")
• out.println("ltligtDay of month ")
• out.println(clock.getDayofMonth())
• out.println("ltligtYear ")
• out.println(clock.getYear())
• out.println("/ltulgt")
• out.println("lt/htmlgt")

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As a JSP page

• lthtmlgt
• Hello World!
• ltbrgt
• ltjspuseBean id"clock"
• class"calendar.JspCalendar"gt
• Today is
• ltulgt
• ltligtDay of monthltclock.getDayofMonth()gt
• ltligtYear ltclock.getYear()gt
• lt/ulgt
• lt/htmlgt

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JSP Basics

• Contains Java or tag library code to help
  generate output for the page
• Text format file
• Looks much like a regular HTML page, but with
  active element sections
• Essentially a form that other code helps fills in
  
• Stored on the server
• a dynamic scripting capability for web pages
• A server side technology can't do any client
  side validation with it.
• When the page is first requested, the JSP is
  compiled into a servlet form and executed.
• Afterwards the JSP script exists as a compiled
  java byte-code (unless it is changed)

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Why use JSP

• JSPs isolate the presentation
• separate processing from display of data
• better implementation of model-view-controller
  (MVC) framework
• The focus is on HTML.
• Java and the JSP extensions assist in making the
  HTML more functional.
• JSPs integrate well with other enterprise Java
  functionality
• JDBC, Servlets, Java Beans, Enterprise Java
  Beans, others
• JSP
• Emphasize components
• Provide a front door to the enterprises Java
  platform

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Benefits of JSP

• Easy and Rapid Web Development, Deployment and
  Maintenance
• Emphasizing Reusable Components
• Separating Content Generation from Presentation
• Open Development and Widespread Industry Support
• Platform Independence
• Simplifying Page Development with Tags

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How do JSPs Work
index.jsp
Servlet/JSP Server
checks
Browser
Forwards to
index.java
Generated Servlet
compiles
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Model-1 Features

• suitable for simple applications
• separation of presentation from content
• not be suitable for complex implementation
• easily lead to an unclear definition of roles and
  allocation of responsibilities.

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Model-2 Features

• suitable for complex applications
• clearest separation of presentation from content
• clear definition of roles and responsibilities of
  the developments and page designers.
• the downside of using the Model 2 approach is its
  complexity

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JSP components

• JSPs have one or more of two types of sections
• 1) template text
• HTML or other markup language
• control the display format
• 2) JSP element
• Java code -or- tags from tag libraries
• specify the data to be displayed

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JSP Elements

• 3 types
• directive
• information or step that is constant across
  requests
• e.g. lt_at_ taglib gt
• action
• action based on information at time JSP is
  requested
• standard or custom (e.g. JSP Standard Tag Library
  JSTL)
• e.g. ltjspuseBeangt (standard) , ltcout gt
  (custom/JSTL)
• scripting
• action to include small piece of code based on
  information at time of request
• e.g. lt out.println(Crust
  request.getParameterValue(Crust)) gt

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Directives

• lt-- a comment --gt - comment text
• lt_at_ page gt - define page-dependent attributes
  re session tracking, error page, buffering, etc.
• lt_at_ include gt - include a file (done when
  translating, not when executing)
• lt_at_ taglib gt - declare a tag library
  containing actions that are used in the page

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Page Directives

• The page directive defines a number of page
  dependent attributes
• lt_at_ page languageJava
• extendsclassName
• importimportList
• session truefalse
• buffernonesizekb
• autoFlushtruefalse
• isThreadSafetruefalse
• errorPagexxx.html
• isErrorPagetruefalse
• gt

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Example

• Gotop
• 4
• page.jsp
• Big5.jsp
• MS950.jsp
• Date.jsp
• errorPage.jsp

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Include Directive

• The include directive is used to inline text
  and/or code at JSP page translation-time.
• lt_at_ include filerelativeURL gt

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Example

• Gotop
• 4
• Include_html.jsp

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Taglib directive
lt_at_ taglib prefix"tags" tagdir"/WEB-INF/tags"
gt lthtmlgt ltheadgt lttitlegtJSP 2.0 Examples -
Hello World Using a Tag Filelt/titlegt lt/headgt
ltbodygt lth1gtJSP 2.0 Examples - Hello World
Using a Tag Filelt/h1gt lthrgt ltpgtThis JSP
page invokes a custom tag that simply echos
"Hello, World!" The custom tag is generated
from a tag file in the /WEB-INF/tags
directory.lt/pgt ltpgtNotice that we did not need
to write a TLD for this tag. We just created
/WEB-INF/tags/helloWorld.tag, imported it using
the taglib directive, and used it!lt/pgt
ltbrgt ltbgtltugtResultlt/ugtlt/bgt
lttagshelloWorld/gt lt/bodygt lt/htmlgt
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Example

• jsp-examples
• Hello World Tag

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JSP Actions

• The syntax for action elements is based on XML
• they have a start tag, a body, and an end tag
• The JSP specification includes some action types
  that are standard.
• New action types are added using the taglib
  directive.

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Standard Action Elements

• ltjspuseBeangt - loading JavaBean
• ltjspgetPropertygt - Displaying Dynamic Content,
  get a property value from a JavaBean and add to
  response
• ltjspsetPropertygt - Initializing a Bean, set a
  JavaBean property value
• ltjspincludegt - include response from servlet or
  JSP during request processing
• ltjspforwardgt - forward processing of request to
  another servlet or JSP
• ltjspparamgt - add a parameter value to a request
  handed off with jspinclude or jspforward
• ltjspplugingt - generates HTML that contains
  browser-dependent elements needed to execute an
  applet with Java Plug-In software

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Standard Actions

• ltjspuseBeangt
• Associates an instance of a bean to a variable to
  use with in the jsp page
• ltjspuseBean idname scopepagerequestsession
  application classclassName typetypeNamegt
• lt/jspuseBeangt

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ltjspuseBeangt

• id variable name to reference instance of class
• scope
• page javax.servlet.jsp.PageContext
• Objects only accessible from within the page
• request ServletRequest
• Objects accessible in pages processing request
  where bean is created
• session HttpSession
• Objects accessible from user session
• application ServletContext
• Objects accessible in pages belonging to same
  application

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Conti.

• Class
• Fully qualified class name that defines the
  implementation of the object
• Type (optional)
• Allows scripting variable to be cast to another
  type from implementation class, java casting
  rules apply.

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ltjspsetPropertygt

• Sets the value of properties in a bean
• 4 cases
• ltjspsetProperty name property /gt
• ltjspsetProperty name property /gt
• ltjspsetProperty name property
  paramName /gt
• ltjspsetProperty name property
  value/gt

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ltjspgetPropertygt

• Gets the value of properties in a bean
• ltjspgetProperty namebeanName
  propertypropertyName/gt
• Name
• Variable name as defined in useBean
• Property
• Name of the bean property to retrieve

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Bean Example

• lthtmlgt
• lttitlegtRandom JSP Testlt/titlegt
• ltbody bgcolorwhitegt
• ltjspuseBean idrnd scopepage
  classrandom.NumberGenerator/gt
• ltulgt
• ltligtNext number is ltjspgetProperty namernd
  propertynextInt/gt
• lt/ulgt
• lt/bodygt
• lt/htmlgt

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Conti.

• package random
• import java.util.
• public class NumberGenerator
• Random rnd new Random()
• public int getNextInt()
• return rnd.nextInt()

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Examples

• Advjhtp1.adrotator.jsp
• jsp-examples.cal.login.html

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Cal1.jsp
Example JspCalendar
Cal2.jsp
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ltjspincludegt

• ltjspincludegt
• Allows you to include resources in the same
  context as the current page
• ltjspinclude pageurl flushtrue/gt
• page
• Relative url
• flush
• If true, buffer is flushed

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Example

• Gotop
• 4
• Jsp_include.jsp
• News.jsp

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ltjspforwardgt

• ltjspforwardgt
• Allows you to dispatch the request to a different
  page
• ltjspforward pageurl/gt
• Example
• Advjhtp1
• forward1.jsp ? forward2.jsp

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ltjspparamgt

• ltjspparamgt
• Used to provide key/value information for
  ltjspincludegt, ltjspforwardgt, and ltjspplugingt
• ltjspparam namename valuevalue/gt
• Name and value are mandatory

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ltjspplugingt

• Creates HTML that contains OBJECT or EMBED
  constructs that result in Java Plugin download
  and execution of Applet
• ltjspplugin typeapplet codeapplet.class
  codebase/htmlgt
• ltjspfallbackgt
• ltpgtCant display appletlt/pgt
• lt/jspfallbackgt
• lt/jspplugingt
• Fallback is used if the plugin cannot be started

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Scripting

• Use directives to set stage
• lt_at_ page languagejava importjava.util. gt
• Several implicit objects
• e.g. out javax.servlet.jsp.JspWriter
• e.g. session javax.servlet.http.HttpSession
• Add Java code
• Using declarations, lt!.........gt.
• With scriptlets, lt...........gt.
• e.g. lt out.println(Crust
  request.getParameterValue(Crust)) gt
• Expressions between lt.....gt.

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Declarations Tag

• Allows you to declare page wide variables and
  methods
• lt! int counter 0 gt
• lt! Vector beanList new Vector() gt

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Scriptlet Tag

• lt gt
• Used to include small pieces of Java code
• lt for(Enumeration e beanList.elements()
  e.hasMoreElements() )
• UserBean uBean (UserBean) e.nextElement()
• out.println( uBean.getUserName() )
• gt

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Expression Tag

• lt gt
• Accepts any Java expression, evaluates the
  expression, converts to a String, and displays.
• lt counter gt
• lt uBean.getUserName() gt
• Short hand for
• lt out.println( uBean.getUserName() ) gt

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Example

• Gotop
• 4
• 99.jsp
• 99_html.jsp

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Implicit Objects

• Objects defined implicitly for use in scripting
  tags
• request, response
• pageContext
• appcontext
• session
• out
• in error pages exception

Example ltif(request.getParameter("first")nul
l) gt lt out.println(String) gt
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Example
lt_at_ page import"hello.NameHandler" gt
ltjspuseBean id"mybean" scope"page

class"hello.NameHandler" /gt ltjspsetProperty
name"mybean" property"" /gt lthtmlgt
ltheadgtlttitlegtHello, Userlt/titlegtlt/headgt ltbody
bgcolor"ffffff" background"background.gif"gt ltta
ble border"0" width"700"gt lttrgt lttd
width"150"gt ltimg src"duke.waving.gif"gt lt/tdgt
lttd width"550"gt lth1gtMy name is Duke.
What's yours?lt/h1gt lt/tdgt lt/trgt
hellouser.jsp
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lttrgt lttd width"150" nbsp lt/tdgt lttd
width"550"gt ltform method"get"gt
ltinput type"text" name"username" size"25"gt
ltbrgt ltinput type"submit"
value"Submit"gt ltinput type"reset"
value"Reset"gt lt/formgt lt/tdgt
lt/trgt lt/tablegt lt if (request.getParameter("userna
me") ! null ) gt lt_at_ include
file"response.jsp" gt lt
gt lt/bodygt lt/htmlgt
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lttable border"0" width"700"gt lttrgt lttd
width"150"gt nbsp lt/tdgt lttd width"550"gt
lth1gtHello, ltjspgetProperty
name"mybean" property"username" /gt!
lt/h1gt lt/tdgt lt/trgt lt/tablegt
response.jsp
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package hello public class NameHandler
private String username public
NameHandler() username null
public void setUsername(
String name ) username name
public String getUsername()
return username
namehandler.java
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Custom Action Elements

• Programmer can develop own actions to extend the
  JSP language
• Example JSP Standard Tag Library (JSTL)
• JSTL Expression Library (EL)
• support expression evaluation
• starts with , ends with
• Other tag libraries now available
• e.g. Jakarta taglib project
• If cant find a tag library that meets your
  needs, can develop a new one

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Expression language (EL)
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EL - implicit object
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Custom Tag Libraries

• Custom-tag libraries
• Encapsulates complex functionality for use in
  JSPs
• Define custom tags
• Used for creating dynamic content
• Classes that implement interface Tag
• Pacakge javax.servlet.jsp.tagext

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Simple Custom Tag
lt-- taglib directive --gt lt_at_ taglib uri
"advjhtp1-taglib.tld" prefix "advjhtp1"
gt lthtml xmlns "http//www.w3.org/1999/xhtml"gt
ltheadgt lttitlegtSimple Custom Tag
Examplelt/titlegt lt/headgt ltbodygt
ltpgtThe following text demonstrates a custom
taglt/pgt lth1gt ltadvjhtp1welcome/gt
lt/h1gt lt/bodygt lt/htmlgt
customTagWelcome.jsp
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lttaglibgt ltshortnamegtadvjhtp1lt/shortnamegt
lttaggt ltnamegtwelcomelt/namegt
lttagclassgt com.deitel.advjhtp1.js
p.taglibrary.WelcomeTagHandler
lt/tagclassgt lt/taglibgt
advjhtp1-taglib.tld
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import java.io. // Java extension
packages import javax.servlet.jsp. import
javax.servlet.jsp.tagext. public class
WelcomeTagHandler extends TagSupport //
Method called to begin tag processing public
int doStartTag() throws JspException
// attempt tag processing try //
obtain JspWriter to output content
JspWriter out pageContext.getOut()
out.print( "Welcome to JSP Tag Libraries!" )
// rethrow IOException to JSP
container as JspException catch(
IOException ioException ) throw new
JspException( ioException.getMessage() )
return SKIP_BODY // ignore the
tag's body
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Custom Tag with Attributes

• Use attributes to customize functionality
• Specify attributes for custom tags

lt-- taglib directive --gt lt_at_ taglib uri
"advjhtp1-taglib.tld" prefix "advjhtp1"
gt lthtml xmlns "http//www.w3.org/1999/xhtml"gt
ltheadgt lttitlegtSimple Custom Tag
Examplelt/titlegt lt/headgt ltbodygt ltpgtThe
following text demonstrates a custom taglt/pgt
lth1gt ltadvjhtp1welcome2 firstName
"Paul" /gt lt/h1gt lt/bodygt lt/htmlgt
customTagWelcome2.jsp
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import java.io. import javax.servlet.jsp. impo
rt javax.servlet.jsp.tagext. public class
Welcome2TagHandler extends TagSupport
private String firstName "" // Method
called to begin tag processing public int
doStartTag() throws JspException try
JspWriter out
pageContext.getOut()
out.print( "Hello " firstName ",
ltbr /gtWelcome to JSP Tag Libraries!" )
// rethrow IOException to JSP
container as JspException catch(
IOException ioException ) throw new
JspException( ioException.getMessage() )
return SKIP_BODY // ignore the
tag's body // set firstName attribute
to the users first name public void
setFirstName( String username )
firstName username
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Evaluating the Body of a Custom Tag

• Custom tags
• Particularly useful for processing element body
• Example

guestBookLogin.jsp
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lt_at_ taglib uri "advjhtp1-taglib.tld" prefix
"advjhtp1" gt lthtml xmlns "http//www.w3.org/19
99/xhtml"gt ltheadgt lttitlegtGuest
Listlt/titlegt ltstyle type "text/css"gt
body font-family tahoma,
helvetica, arial, sans-serif
table, tr, td, th text-align
center font-size .9em
border 3px groove padding 5px
background-color dddddd
lt/stylegt lt/headgt
guestBookLogin.jsp
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ltbodygt ltp style "font-size 2em"gtGuest
Listlt/pgt lttablegt lttheadgt
ltth style "width 100px"gtLast namelt/thgt
ltth style "width 100px"gtFirst
namelt/thgt ltth style "width
200px"gtEmaillt/thgt lt/theadgt
lt-- guestlist custom tag --gt
ltadvjhtp1guestlistgt lttrgt
lttdgtlt lastName gtlt/tdgt
lttdgtlt firstName gtlt/tdgt lttdgt
lta href "mailtolt email gt"gt
lt email gtlt/agt
lt/tdgt lt/trgt
lt/advjhtp1guestlistgt lt/tablegt
lt/bodygt lt/htmlgt
This tag will be executed repeatedly until it
receives SKIP_BODY
guestBookLogin.jsp
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lttaggt ltnamegtguestlistlt/namegt
lttagclassgt com.deitel.advjhtp1.jsp.taglib
rary.GuestBookTag lt/tagclassgt
ltteiclassgt com.deitel.advjhtp1.jsp.taglib
rary.GuestBookTagExtraInfo lt/teiclassgt
ltbodycontentgtJSPlt/bodycontentgt
ltinfogt Iterates over a list of GuestBean
objects lt/infogt lt/taggt
advjhtp1-taglib.tld
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guestBookLogin.jsp
GuestBookTag
BodyTagSupport
doStartTag()
create guestData
if guestData ! null
processNextGuess
type of firstName?
Create a session object "firstName"
display "firstName"
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TagSupport
doStartTag()
EVAL_BODY_INCLUDE
Execute body content
SKIP_BODY
SKIP_PAGE
EVAL_PAGE
doEndTag()
release
release
stop this page
Continue this page
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BodyTagSupport
doStartTag()
EVAL_BODY_TAG
getBodyContent() doInitBody()
SKIP_BODY
Execute body content
EVAL_BODY_TAG
SKIP_PAGE
EVAL_PAGE
doEndTag()
doAfterBody()
release
release
stop this page
Continue this page
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Container
SKIP_BODY
SKIP_BODY
doStartTag
doAfterBody
EVAL_BODY_TAG
EVAL_BODY_TAG
processNextGuest()
GuestBookTag ExtraInfo()
GuestBookTag.java
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Tag library example-4

• gotop.12.Myfont.jsp

In this program, MyFont.java has
implemented doEndTag, why?
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Tag library example-5

• gotop.12.Filter.jsp

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File Upload

• Use com.oreilly.servlet.MultipartRequest

ltform name"Form1" enctype"multipart/form-data"
method"post" action"Fil2.jsp"gt ltpgt ???? 1
ltinput type"file" name"File1" size"20"
maxlength"20"gt lt/pgt
MultipartRequest multi new MultipartRequest(requ
est , saveDirectory , maxPostSize )

upload
directory max size
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Conti.

• Example gotop.7.file.htm

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Java Mail

• Use mail.jar and activation.jar

lt_at_ page language"java" import"java.util.,java.
io." gt lt_at_ page import"javax.mail." gt lt_at_
page import"javax.mail.internet." gt lt_at_ page
import"javax.activation." gt
// ??????Mail ???????????? java.util.Properties
props System.getProperties()
props.put("mail.host",mailserver)
props.put("mail.transport.protocol","smtp")
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// ????Session ?? javax.mail.Session
mailSession javax.mail.Session.getDefaultInst
ance(props,null) Message msg new
MimeMessage(mailSession) // ??????????
msg.setFrom(new InternetAddress(From)) //
????????????? address InternetAddress.parse(to
,false) msg.setRecipients(Message.RecipientType
.TO, address) // ???????, ??, MIME Type
msg.setSubject(Subject) msg.setSentDate(new
Date()) msg.setText(messageText) //
?? Transport.send(msg)
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JavaMail sending mail with files

• Use com.oreilly.servlet.MultipartRequest

File file new File(FileName)
// ????????,????????????
MimeBodyPart mbp1 new
MimeBodyPart() //
?????????? text/html ,?? HTML ??
mbp1.setContent(messageText.toString(),"text/html"
) // ????????
MimeBodyPart mbp2 new MimeBodyPart()
FileDataSource fds new FileDataSource(FileNa
me) mbp2.setDataHandler(new
DataHandler(fds))
mbp2.setFileName(fds.getName())
// ??????????,???????? Multipart mp
new MimeMultipart()
mp.addBodyPart(mbp1)
mp.addBodyPart(mbp2)
msg.setContent(mp)