COSC 2956 Internet Tools

1
COSC 2956 Internet Tools

• Java Server Pages

2
What is a Java Server Page

• A JSP combines Java code and template HTML in a
  single file.
• This is similar to the way PHP works.
• Scripting elements are used to provide dynamic
  pages

3
Connection with servlets

• Each Java server page is compiled into a servlet
  before it can be used
• This is normally done when the first request is
  made so there could be a short wait.
• However, JSP's can be precompiled so there is no
  wait.

Java ServerPage
page
translation
Java servletsource code
Java Servletclass file
compiler
(show an example)
4
Translated servlets

• You can example the source code produced by the
  JSP translation process.
• There is a directory called work in the main
  tomcat directory where you can find the source
  code.
• Note that the _jspService method corresponds to
  the servlet service method (which is called by
  doGet or doPost)

5
JSP elements (overview)

• Directives of the form lt_at_ ... gt
• Scripting elements
• Expressions of the form lt expr gt
• Scriptlets of the form lt code gt
• Declarations of the form lt! code gt
• JSP Comments lt-- ... --gt
• Standard actions
• Example ltjspuseBeangt ... lt/jspuseBeangt
• Implicit variables like request, response, out

6
Directives

• They have the form

lt_at_ name attribute1"...", attribute2"..." ... gt
Specify page properties
page include taglib
Include a file at translation time
Specify custom tags
7
Directives examples

• Import java packages
• lt_at_ pageimport"java.util.,java.sql." gt
• Multiple import statements
• lt_at_ page import"java.util." gtlt_at_ page
  import"java.sql." gt
• including file at translation time
• lt_at_ include file"header.html" gt
• For include the path is relative to the jsp

8
Scripting elements expression

• For an expression scripting element like lt
  expr gt, expr is evaluated and the result is
  converted to a string and placed into the JSP's
  servlet output stream. In a Java servlet this
  would be equivalent to

PrintWriter out response.getWriter()...out.pr
int(expr)
9
Expression examples

• Displaying request parameters (request is an
  implicit object available in a JSP)
• Doing calculations

Your name is lt request.getParameter("name")
gtand your age is lt request.getParameter("age")
gt
The value of pi is lt Math.PI gt and the square
rootof two is lt Math.sqrt(2.0) gt and today's
date islt new java.util.Date() gt.
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Scripting elements scriptlet

• For a scriplet lt statements gt the Java
  statements are placed in the translated servlet's
  _jspService method body (it's like the servlet
  service method which calls either doGet or doPost)

public void _jspService(HttpServletRequest
request, HttpServletResponse response) throws
java.io.IOException, ServletException...
statements ...
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Scriplet examples

• Check a request parameter

lt String name request.getParameter("name")
if (name null) gt lth3gtPlease supply
a namelt/h3gtlt else gt
lth3gtHello lt name gtlt/h3gtlt gt
There are 3 scriptlets here and an expression
element
12
Scripting elementsdeclaration

• For a declaration lt! declarations gt the Java
  statements are placed in the class outside the
  _jspService method. Typical declarations can be
  Java instance variable declarations or Java
  methods

// declarations would go herepublic void
_jspService(...) ...
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Declaration examples

• Declaring instance variables
• Declaring methods

lt! private int count 0 gt...The count is
lt count gt.
lt!private int toInt(String s) return
Integer.parseInt(s)gt
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Including files

• Including files at translation time (when JSP is
  translated to a servlet)
• Including files at request time

lt_at_ include file"filename" gt
ltjspinclude page"filename" flush "true" /gt
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Where do you put JSP's ?

• If you have a web application called c2206 then
  create a directory called jsp below it and put
  JSP's there
• For example a JSP called test.jsp would have the
  path c2206/jsp/test.jsp
• To run this JSP use the URL
• http//localhost8080/c2206/jsp/test.jsp

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A simple JSP
lthtmlgtltheadgtlttitlegtJSP Testlt/titlegtlt/headgtltbodygt
lth1gtJSP Testlt/h1gtTime lt new java.util.Date()
gtlt/bodygtlt/htmlgt
The expression scripting element lt ... gt
isequivalent to the scriptlet lt
out.print(...) gt
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The implicit out object

• In a scriptlet lt ... gt you can use the out
  object to write to the output stream
• Example

lt out.print("The sum is ") out.print("1
2 " (12))gt
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The implicit request object

• Example

lthtmlgtltheadgtlttitlegt...lt/titlegtlt/headgtltbodygtlth1gt
...lt/h1gtltpgtlt request.getParameter("greeting")
gtlt/pgtlt/bodygtlt/htmlgt
Try this using http//localhost8080/c2206/jsp/si
mple/greeting0.jsp?greetingHello Frank
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Processing form using GET
lthtmlgtltheadgtlttitlegtJSP Processing
...lt/titlegtlt/headgtltbodygtlth1gtJSP Processing form
with GETlt/h1gtltform action"doForm1.jsp"
method"GET"gtFirst name ltinput type"text"
name"firstName"gtltbr /gtLast name ltinput
type"text" name"lastName"gtltpgtltinput
type"submit" name"button"
value"SubmitName"gtlt/pgtlt/formgtlt/bodygtlt/htmlgt
c2206/jsp/forms/form1_get.html
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Processing form using POST
lthtmlgtltheadgtlttitlegtJSP Processing
...lt/titlegtlt/headgtltbodygtlth1gtJSP Processing form
with POSTlt/h1gtltform action"doForm1.jsp"
method"POST"gtFirst name ltinput type"text"
name"firstName"gtltbr /gtLast name ltinput
type"text" name"lastName"gtltpgtltinput
type"submit" name"button"
value"SubmitName"gtlt/pgtlt/formgtlt/bodygtlt/htmlgt
c2026/jsp/forms/form1_post.html
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doForm1.jsp
lt_at_ include file"../doctype.html" gtltheadgt
lttitlegtJSP Form Resultslt/titlegtlt/headgtltbodygtlth1
gtJSP Form Resultslt/h1gtHello lt
request.getParameter("firstName") gtlt
request.getParameter("lastName")
gtlt/bodygtlt/htmlgt
c2206/jsp/forms/doForm1.jsp
Try this using http//localhost8080/c2206/jsp/fo
rms/form1_get.html
22
Temperature conversion
input
output
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temperature.jsp (1)
lt_at_ page import"java.text.DecimalFormat"
gtlthtmlgtltheadgtlttitlegtFahrenheit ...
Conversionlt/titlegtlt/headgtltbodygtlth1gtFahrenheit
to Celsius Conversionlt/h1gtlt String self
request.getRequestURI() if (request.getParamet
er("convert") null) gt ltform
action"lt self gt" method"POST"gt Fahrenheit
temperature ltinput type"text"
name"fahrenheit" /gt ltpgtltinput type"submit"
name"convert" value"Convert to
Celsius" /gtlt/pgt lt/formgt
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temperature.jsp (2)
lt else double fahr 0.0
try fahr Double.parseDouble(
request.getParameter("fahrenheit"))
catch (NumberFormatException e)
// do nothing, accept default value

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temperature.jsp (3)
double celsius (fahr - 32.0)
(5.0/9.0) DecimalFormat f2 new
DecimalFormat("0.00")gt lt
f2.format(fahr) gtF is lt
f2.format(celsius) gtC ltpgtlta href"lt self
gt"gtAnother conversionlt/agt lt/pgtlt
gtlt/bodygtlt/htmlgt
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Java Beans

• Special classes that encapsulate some data
• They have a default constructor
• get and set methods for data fields (properties)
• A bean can be constructed in JSP using
• ltjspuseBean id "..." class "..." /gt
• If the bean already exists this statement does
  nothing

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setting properties

• To set a property of a bean useltjspsetProperty
  name"..." property"..." value"..." /gt
• To set a property using the value of a request
  parameter useltjspsetProperty name"..."
  property"..." param"..." /gt

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getting properties

• To get a property of a bean useltjspgetProperty
  name"..." property"..." /gt

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A Greeting bean
package beanspublic class Greeting private
String greeting // the property public
Greeting() greeting "Hello World"
public String getGreeting() return greeting
public void setGreeting(String g)
greeting (g null) ? "Hello World" g
beans/Greeting.java
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Naming convention

• If the property name is greeting
• the get method must have the name getGreeting
• the set method must have the name setGreeting

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Creating a Greeting bean (1)

• Create a bean and use default property
• Create a bean and set its property when it is
  constructed
• Here ltjspsetPropertygt is in the body of the
  ltjspuseBeangt element.

ltjspuseBean id"hello" class"beans.Greeting" /gt
ltjspuseBean id"hello" class"beans.Greeting"
gtltjspsetProperty name"hello"
property"greeting" value"Hello JSP World"
/gtlt/jspuseBeangt
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Creating a Greeting bean (2)

• Create a bean and set its property after it has
  been constructed
• The ltjspsetPropertygt tag is now outside the
  ltjspuseBeangt tag so it will always set the
  property, not just when the bean is constructed

ltjspuseBean id"hello" class"beans.Greeting"
/gtltjspsetProperty name"hello"
property"greeting" value"Hello JSP World" /gt
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greeting1.jsp
ltjspuseBean id"hello" class"beans.Greeting"
/gtltjspsetProperty name"hello"
property"greeting" value"Hello JSP World"
/gtlthtmlgtltheadgtlttitlegtGreeting JSP that uses a
Greeting beanlt/titlegtlt/headgtltbodygtlth1gtGreeting
JSP that uses a Greeting beanlt/h1gtltpgtltjsp.getProp
erty name"hello" property"greeting"
/gtlt/pgtlt/bodygtlt/htmlgt
test/jsp/greeting1.jsp
http//localhost8080/test/jsp/greeting1.jsp
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Two beans

• One initialized explicitlyand the other is
  initializedusing a request parameter

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greeting2.jsp
ltjspuseBean id"greet1" class"beans.Greeting"
/gtltjspuseBean id"greet2" class"beans.Greeting"
/gtltjspsetProperty name"greet1"
property"greeting" value"Hello JSP World"
/gtltjspsetProperty name"greet2"
property"greeting" param"greeting"
/gtlthtmlgtltheadgtlttitlegtGreeting JSP using two
Greetingbeanslt/titlegtlt/headgtltbodygtlth1gtGreeting
JSP using two Greeting beanslt/h1gtltpgt1st bean
ltjspgetProperty name"greet1"
property"greeting" /gtlt/pgtltpgt2nd bean
ltjspgetProperty name"greet2"
property"greeting" /gtlt/pgtlt/bodygtlt/htmlgt
test/jsp/greeting2.jsp
http//localhost8080/test/jsp/greeting2.jsp
http//localhost8080/test/jsp/greeting2.jsp?greet
ingHelloFred
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three beans and include file

• One initialized explicitly, one isinitialized
  using a requestparameter, and one isinitialized
  using getParameter

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greeting3.jsp (1)
ltjspuseBean id"greet1" class"beans.Greeting"
/gtltjspuseBean id"greet2" class"beans.Greeting"
/gtltjspuseBean id"greet3" class"beans.Greeting
" /gtltjspsetProperty name"greet1"
property"greeting" value"Hello JSP World"
/gtltjspsetProperty name"greet2"
property"greeting" param"greeting" /gtlt--
Following works but param method is better
--gtltjspsetProperty name"greet3"
property"greeting" value"lt
request.getParameter(\"greeting\") gt" /gt
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greeting3.jsp (2)
lt-- Include file contains doctype and html tag
--gtltjspinclude page"doctype.html"
flush"true" /gtltheadgtlttitlegtGreeting
JSPlt/titlegtlt/headgtltbodygtlth1gtGreeting
JSPlt/h1gtltpgt1st bean ltjspgetProperty
name"greet1" property"greeting"
/gtlt/pgtltpgt2nd bean ltjspgetProperty
name"greet2" property"greeting"
/gtlt/pgtltpgt3rd bean ltjspgetProperty
name"greet3" property"greeting"
/gtlt/pgtltpgtrequest lt request.getParameter("greet
ing") gtlt/pgtlt/bodygtlt/htmlgt
test/jsp/greeting3.jsp
http//localhost8080/test/jsp/greeting3.jsp
http//localhost8080/test/jsp/greeting3.jsp?greet
ingHelloFred
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Beans and forms

• Using a bean to represent the data of a form

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form1_bean.html (1)
lthtmlgtltheadgtlttitlegtJSP Processong form using a
beanlt/titlegtlt/headgtltbodygtlth1gtJSP Processing
form using a beanlt/h1gtltform action"doForm1Bean.j
sp" method"GET"gtFirst name ltinput type"text"
name"firstName"gtlt/ brgtLast name ltinput
type"text" name"lastName"gtltpgtltinput
type"submit" name"button" value"Submit
Name"gtlt/pgtlt/formgtlt/bodygtlt/htmlgt
test/jsp/forms/form1_bean.html
http//localhost8080/test/jsp/forms/form1_bean.ht
ml
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A Name bean
package beanspublic class NameBean private
String firstName // property private String
lastName // property public String
getFirstName() return firstName public
String getLastName() return lastName
public void setFirstName(String first)
firstName first public void
setLastName(String last) lastName last
beans/NameBean.java
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doForm1Bean.jsp
ltjspuseBean id"name" class"beans.NameBean"
/gtltjspsetProperty name"name" property""
/gtltjspinclude page"../doctype.html"
flush"true" /gtltheadgtlttitlegtJSP Form results
using a beanlt/titlegtlt/headgtltbodygtlth1gtJSP Form
results using a beanlt/h1gtHelloltjspgetProperty
name"name" property"firstName"
/gtltjspgetProperty name"name"
property"lastName" /gtlt/bodygtlt/htmlgt
test/jsp/forms/doForm1Bean.jsp
Note the use of property"" to set all the bean
propertiesusing the form data vaules
43
MVC approach

• MVC stands for Model-View-Controller
• Controller
• controls the application by getting the input and
  forwarding the request to the appropriate page
• View
• visual appearance of the output data
• Model
• logic, calculations necessary to produce the
  data. Sometimes called business logic

44
MVC example (Temperature)

• Getting the input (Fahrenheit temperature)
• controller.jsp (dispatch (forward) request)
• form.jsp (user input of temperature)
• Displaying the output (Celsius temperature)
• response.jsp
• Model (logic and calculations done by beans)
• TemperatureBean.java (form data)
• TemperatureCalculatorBean.java(does the
  temperature conversio)

45
TemperatureBean
package beanspublic class TemperatureBean
private String temp public String
getTemperature() return temp
public void setTemperature(String t) temp
t
beans/TemperatureBean.java
46
TemperatureCalculatorBean
package beansimport java.text.DecimalFormatpub
lic class TemperatureCalculatorBean private
double celsius public String
getTemperature() return new
DecimalFormat("0.00").format(celsius)
// continued on next slide
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TemperatureCalculatorBean
public void setTemperature(String fahr)
double f try f
Double.parseDouble(fahr) catch
(NumberFormatException e) f
0.0 celsius (f - 32.0) (5.0 /
9.0)
beans/TemperatureCalculatorBean.java
48
Forwarding a page

• A JSP can forward the request to another page
  using
• ltjspforward page"file.jsp" /gt
• The important idea here is that this new page
  receives all the request parameters of the
  forwarding page.

49
controller.jsp
ltjspuseBean id"temp" class"beans.TemperatureBea
n"gtltjspsetProperty name"temp" property""
/gtlt/jspuseBeangtlt if (request.getParameter("tem
perature") null) gt ltjspforward
page"form.jsp" /gtlt else gt
ltjspforward page"response.jsp" /gtlt gt
test/jsp/temperature/controller.jsp
http//localhost8080/test/jsp/temperature/control
ler.jsp
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form.jsp
ltjspinclude page"../doctype.html" flush"true"
/gtltheadgtlttitlegtFahrenheit to Celsius
Conversionlt/titlegtlt/headgtltbodygtlth1gtFahrenheit
to Celsius Conversionlt/h1gtltform
action"controller.jsp" method"GET"gtFahrenheit
temperatureltinput type"text"
name"temperature"gtlt/ brgtltinput type"submit"
name"button" value"Submit Temperature"gtlt/pgtlt
/formgtlt/bodygtlt/htmlgt
test/jsp/temperature/form.jsp
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response.jsp
ltjspuseBean id"temp" class"beans.Temperature"
scope"request" /gtltjspuseBean id"convert"
class"beans.TempertureCalculatorBean"
/gtltjspsetProperty name"convert"
property"temperature" value"lt
temp.getTemperature() gt" /gtltjspinclude
page"../doctype.html" flush"true"
/gtltheadgtlttitlegtFahrenheit to Celsius
Conversionlt/titlegtlt/headgtltbodygtlth1gtFahrenheit to
Celsius Conversionlt/h1gtltjspgetProperty
name"temp" property"temperature" /gtFahrenheit
isltjspgetProperty name"convert"property"tempe
rature" /gt Celsius.ltpgtlta href"controller.jsp"gtCo
nvert another .. lt/agtlt/pgtlt/bodygtlt/htmlgt
test/jsp/temperature/response.jsp
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Databases using JSP

• Display the books database table
• bookdisplay1.jsp
• BookBean.java
• BookDataBean.javaDBConnectorBean.java

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bookdisplay1.jsp (1)
lt_at_ page import"java.text., java.util.,
beans." gtltjspuseBean id"db"
class"DBConnectorBean" gt ltjspsetProperty
name"db" property"driver" value"lt
application.getInitParameter(
\"jdbc.driver\") gt"/gt
ltjspsetProperty name"db" property"url"
value"lt application.getInitParameter(
\"jdbc.url\") gt"/gt
ltjspsetProperty name"db" property"username"
value"lt application.getInitParameter(
\"jdbc.username\") gt"/gt
ltjspsetProperty name"db" property"password"
value"lt application.getInitParameter(
\"jdbc.password\")
gt"/gtlt/jspuseBeangt
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bookdisplay1.jsp (2)
ltjspuseBean id"book" class"BookBean"/gtltjspus
eBean id"bookDataBean" class"BookDataBean"gt
ltjspsetProperty name"bookDataBean"
property"connection" value"lt
db.getConnection()gt"/gtlt/jsbuseBeangtlt!
DecimalFormat cents new DecimalFormat("0.00")
gtltjspinclude page"doctype.html" flush"true"
/gtltheadgtlttitlegtDisplaying the books database
tablelt/titlegtlt/headgtltbodygtlth1gtDisplaying the
books database tablelt/h1gt
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bookdisplay1.jsp (3)
lttable border"1"gtlttrgt ltthgtISBNlt/thgtltthgtTITLElt
/thgtltthgtAUTHORlt/thgt ltthgtPUBlt/thgtltthgtYEARlt/thgtltt
hgtPRICElt/thgtlt/trgtlt Iterator
bookListIterator bookDataBean.getIterator
() while (bookListIterator.hasNext())
book (BookBean) bookListIterator.next()gt
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bookdisplay1.jsp (4)
lttrgtlttdgtlt book.getIsbn() gtlt/tdgtlttdgtlt
book.getTitle() gtlt/tdgtlttdgtlt book.getAuthor()
gtlt/tdgtlttdgtlt book.getPub() gtlt/tdgtlttdgtlt
book.getYear() gtlt/tdgtlttdgtlt cents.format(book.g
etPrice()) gtlt/tdgtlt/trgt lt gtlt/tablegtlt/bod
ygtlt/htmlgt
test/jsp/bookdisplay1.jsp
http//localhost8080/test/jsp/bookdisplay1.jsp