CS4273: Distributed System Technologies and Programming I

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CS4273 Distributed System Technologies and
Programming I

• Lecture 11 JavaServer Pages (JSP)

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JavaServer Pages (JSP)

• Why JSP?
• Get rid of Java programming.
• Separate presentation from business logic.
• Reuse predefined components, such as JavaBean,
  tag libraries.
• How does JSP work?
• The entire JSP page gets translated into a
  Servlet (once) at the first time it is invoked.
• It is the Servlet code that gets executed at each
  request. No interpretation of JSP occurs at
  request time. The original JSP page is totally
  ignored at request time.
• JSP tutorial website
• http//www.jsptut.com/
• http//java.sun.com/products/jsp/docs.html

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Example of a Translated JSP

• The original JSP
• ltH1gtA Random Numberlt/H1gt
• lt Math.random() gt
• The resulting Servlet code
• public void _jspService(HttpServletRequest
  request,
• HttpServletResponse
  response)
• throws ServletException, IOException
• response.setContentType("text/html")
• HttpSession session request.getSession(true
  )
• JspWriter out response.getWriter()
• out.println("ltH1gtA Random Numberlt/H1gt")
• out.println(Math.random())
• ...

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JSP Notations

• JSP can include Java code, applets, servlets,
  JavaBeans, etc.
• JSP Expressions lt expression gt
• JSP Scriptlets (for Java code) lt Java-code gt
• JSP Declarations lt! declarations gt
• JSP Directives lt_at_ directive gt
• e.g., lt_at_ page import java.util.gt
• lt_at_ include file banner.htmlgt

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The First JSP example

• JSP files in dir jia/www/java/js/jsp/
• URL for run JSP http//jserv.cs.cityu.edu.hk8080
  /jia/jsp/jspDate.jsp
• lt-- file jia/www/java/js/jsp/jspDate.jsp--gt
• lthtmlgt
• ltheadgtlttitlegt Simple JSP Test Pagelt/titlegtlt/headgt
• ltbodygt
• lth1 aligncentergtSimple JSP Test Pagelt/h1gt
• lttable aligncentergt
• lttrgt lttdgt Now, the time is lt/tdgt
• lttdgt lt new java.util.Date() gt lt/tdgt
• lt/trgt
• lt/tablegt
• lt/bodygtlt/htmlgt

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An Example of JSP Scriptlets (Java code)

• ltHTMLgt
• ltBODYgt
• The time returned from a java utility function
• lt
• // This scriptlet declares and initializes
  "date"
• java.util.Date date new java.util.Date()
• out.println( date )
• out.println( "ltBRgtYour machine's address is
  " )
• // request in next line is in servlet style
• out.println( request.getRemoteHost())
• gt
• lt/BODYgt
• lt/HTMLgt

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An Example of JSP Declaration and Directives

• lt-- the next line is a JSP directive --gt
• lt_at_ page import"java.util." gt
• ltHTMLgt
• ltBODYgt
• lt!-- following is a JSP declaration of function
  getDate --gt
• lt!
• Date getDate()
• Date theDate new Date()
• return theDate
• gt
• lt!-- the next line has JSP expression --gt
• The time returned from java declared function
  is lt getDate() gt
• lt/BODYgt
• lt/HTMLgt

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Another Example of Scriptlet

• lt-- filename welcome.jsp --gt
• lthtmlgtltheadgt
• lttitlegtExample of JSP Scriptletlt/titlegt
• lt/headgt
• ltbodygt
• lt // begin scriptlet
• String name
• request.getParameter( "firstName" )
• if ( name ! null )
• gt
• lth1gtHello lt name gt, ltbr /gt
• Welcome to JavaServer Pages!lt/h1gt
• lt // continue scriptlet
• // end if
• else
• gt

• ltform action "welcome.jsp" method "GET"gt
• ltpgtType your first name and press Submitlt/pgt
• ltpgtltinput type "text" name "firstName" /gt
• ltinput type "submit" value
  "Submit"/gt
• lt/pgt
• lt/formgt
• lt // continue scriptlet
• // end else
• gt lt-- end scriptlet --gt
• lt/bodygt
• lt/htmlgt

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JSP Directives

• JSP directives are used for specifying page
  settings at translation time. Three directives
  page, include, and taglib.
• page directive define the page setting.
• e.g., lt_at_ page import java.util.gt
• include directive insert a file at
  translation-time as if it were originally part of
  the JSP (note. jspinclude inserts a file at
  request time!).
• e.g., lt_at_ include file banner.htmlgt
• taglib directive specify user-defined tag
  libraries.
• e.g., lt_at_ taglib prefixblx uri/blx.tld gt

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JSP Standard Actions

• JSP actions allow some common tasks in JSP. JSP
  containers process
• actions at request time
• ltjspincludegt. Include a file at request time
  (Note. The include directive inserts a file at
  translation time)
• e.g., ltjspinclude page banner.htmlgt
• ltjspforwardgt. Forward the processing to another
  JSP or servlet. This terminates the current JSPs
  execution.
• e.g., ltjspforward page errorProcess.jspgt
• ltjspplugingt. Allow a browser-object (applets) or
  html element embedded in jsp. Its passed to
  browser without being executed in server!
• e.g., ltjspplugin type"applet"
  codemyApplet.class
• width"475" height"350"gtlt/jspplugingt

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JSP Standard Actions (Cont.)

• ltjspparamgt. Pass parameters to another JSP or
  servlet (used together with include, forward, and
  plugin).
• ltjspuseBeangt. Specify scope of a JavaBean and
  assign id.
• e.g. ltjspuseBean id"numguess"
  class"num.NumberGuessBean" scope"session"/gt
• The next two actions are used with JavaBean
  instance
• ltjspsetPropertygt
• ltjspgetPropertygt

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Example of jspforward and jspparam

• lt
• // end if
• else
• gt
• ltform action "forwardExample.jsp"
• method "GET"gt
• ltpgtType your first name and press Submitlt/pgt
• ltpgtltinput type "text" name "firstName" /gt
• ltinput type "submit" value "Submit"/gtlt/pgt
• lt/formgt
• lt
• // end else
• gt
• lt/bodygt
• lt/htmlgt

• lt-- filename forwardExample.jsp --gt
• lthtmlgtltheadgt
• lttitlegtForward request to another JSPlt/titlegt
• lt/headgt
• ltbodygt
• lt // begin scriptlet
• String name request.getParameter(
  "firstName" )
• if ( name ! null )
• gt
• ltjspforward page "forwardJSP.jsp"gt
• ltjspparam name "date" value
• lt new java.util.Date() gt/gt
• lt/jspforwardgt

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Example of JSP forward and jspparam (Cont.)

• lt-- filename forwardJSP.jsp --gt
• lthtmlgt
• ltheadgt
• lttitlegtProcessing a jspforward requestlt/titlegt
• lt/headgt
• ltbodygt
• ltpgt Hello lt request.getParameter( "firstName"
  ) gt, ltbr /gt
• Your request was received ltbr /gt
• and forwarded at lt request.getParameter(
  "date" ) gt
• lt/bodygt
• lt/htmlgt

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Example of JSP useBean

• The program numguess.jsp uses a JavaBean object
  NumberGuessBean.class, which is in
  /js/WEB-INF/classes/num. See NumberGuessBean.java
  for lib routines.

lt_at_ page import "num.NumberGuessBean"gt ltjspuseB
ean id"numguess" class"num.NumberGuessBean"
scope"session"/gt ltjspsetProperty
name"numguess" property""/gt lthtmlgt ltheadgtlttitle
gtNumber Guesslt/titlegtlt/headgt ltbody
bgcolor"white"gt lt if (numguess.getSuccess())
gt Congratulations! You got it. And after
just lt numguess.getNumGuesses() gt tries.ltpgt
lt numguess.reset() gt
Would you lta href"numguess.jsp"gt try
againlt/agt? lt else if (numguess.getNumGuesses()
0) gt Welcome to the Number Guess
game.ltpgt Ive a number between 1 and
100.ltpgt ltform method GETgt What's your guess?
ltinput typetext name guessgt ltinput
typesubmit value"Submit"gt lt/formgt .lt/bodygt
lt/htmlgt
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Example of JSP Tag Library (taglib)

• Directive taglib allows user defined tags,
  facilitating the use of large amount of Java
  libraries in jsp (separate JSP from Java-code
  implementations). Three files involved for
  taglib
• JSP file, specifying the use of taglib, e.g.,
  SendMail.jsp
• lt_at_ taglib prefixsend" uri./taglib.tld"
  gt // send is prefix you can use
• ltHTMLgtltBODYgt
• lt String email request.getParameter( "email"
  ) gt
• ltsendemail host"yoursmtphost.com"
  from"you_at_email.com"gt
• ltblxemailTogtlt email gtlt/blxemailTogt
• lt/sendemailgt
• Tag Library Descriptor file (.tld) in XML format,
  taglib.tld, specify format of lib routines, such
  as routine names, parameters, etc.
• lttaggtltnamegtSendmaillt/namegt
• lttagclassgtcom.cj.smtp.Sendmaillt/tagclassgt
• ltteiclassgtcom.cj.smtp.BoolVariablelt/teiclassgt
• Library routines (java class file), sendmail.jar
  in WEB-INF/lib (for you only) or
  jserv/usr/jt/lib (for all users). See dir
  setting in http//www.jsptube.com/servlet-tutorial
  s/web-application-directory-structure.html
• Use jar tvf blazix.jar cmd to see the list of
  routines in class file.

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JSP JDBC Example

• lt_at_ page contentType"text/htmlcharsetutf-8"gt
• lt_at_ page import"java.sql." gt
• ltHTMLgtltHEADgt
• ltTITLEgtJSP JDBClt/TITLEgtlt/HEADgt
• ltBODYgt
• ltcentergtJSP JDBClt/centergt
• ltBRgtltBRgt
• lttable border3 aligncenter gt
• lt
• Class.forName("com.mysql.jdbc.Driver")
• String url jdbcmysql//jserv.cs.cityu.edu.hk3
  306/db_jdemo
• Connection con DriverManager.getConnection(url,
  "jdemo","apple1")
• Statement stmtcon.createStatement()
• String sql"select COF_NAME, PRICE from COFFEES"

• ResultSet rsstmt.executeQuery(sql)
• while(rs.next())
• out.print("ltTRgtltTDgt"
• rs.getString("COF_NAME")"lt/TDgt")
• out.print("ltTDgt"
• rs.getString("PRICE")"lt/TDgtlt/TRgt"
  )
• gt
• lt/tablegt
• ltBRgtltHRgt
• lt rs.close() stmt.close() con.close() gt
• lt/BODYgt
• lt/HTMLgt