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Chapter 2: Using Objects

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Title: Chapter 2: Using Objects

1
Lecture 12
Introducing JAVA SERVER Pages
2
JSP Application Development

Using Scripting Elements

3
Implicit JSP Objects

When you use scripting elements in a JSP page,
you always have access to a number of objects
that JSP container makes available.
Note All variable names listed on next page are
reserved for the implicit objects. If you declare
your own variables in a JSP page, you must not
use these reserved names for other variables.

4
Implicit JSP Objects
5
Using JavaBeans Properties

lt_at_ page language"java" contentType"text/html"
gt
lthtmlgt
ltbody bgcolor"white"gt
ltjspuseBean id"clock" class"java.util.Date" /gt
lt if (clock.getHours() lt 12) gt
Good morning!
lt else if (clock.getHours() lt 17) gt
Good day!
lt else gt
Good evening!
lt gt
lt/bodygt
lt/htmlgt

6
Using Request Information

lt_at_ page language"java" contentType"text/html"
gt
lthtmlgt
ltbody bgcolor"white"gt
lt if (request.getHeader("User-Agent").indexOf("MS
IE") ! -1) gt
You're using Internet Explorer.
lt
else
if (request.getHeader("User-Agent").indexOf("
Mozilla") ! 1)
gt
You're using Netscape.
lt else gt
You're using a browser I don't know about.
lt gt
lt/bodygt
lt/htmlgt

7
Working with Arrays

lt_at_ page language"java" contentType"text/html"
gt
lthtmlgt
ltbody bgcolor"white"gt
ltform action"loop.jsp"gt
ltinput type"checkbox" name"fruits"
value"Apple"gtAppleltbrgt
ltinput type"checkbox" name"fruits"
value"Banana"gtBananaltbrgt
ltinput type"checkbox" name"fruits"
value"Orange"gtOrangeltbrgt
ltinput type"submit" value"Enter"gt
lt/formgt

lt
String picked request.getParameterValues("
fruits")
if (picked ! null picked.length ! 0)
gt
You picked the following fruits
ltulgt
lt
for (int i 0 i lt picked.length i)
out.println("ltligt" pickedi)
gt
lt/ulgt
lt gt
lt/bodygt
lt/htmlgt

9
Displaying values

A JSP expression element can be used instead of
the
ltjsp getPropertygt action element in some places.
An expression starts with lt and ends with
gt
The result of the expression is written to the
response body.
The code in an expression must not end with
semicolon.

10
userInfo4.java

lt_at_ page language"java" contentType"text/html"
gt
lt_at_ page import"com.ora.jsp.util." gt
lthtmlgt
ltheadgt
lttitlegtUser Info Entry Formlt/titlegt
lt/headgt
ltbody bgcolor"white"gt
ltjspuseBean id"userInfo" class"com.ora.jsp.
beans.userinfo.UserInfoBean"gt
ltjspsetProperty name"userInfo"
property"" /gt
lt/jspuseBeangt
lt-- Output list of values with invalid
format, if any --gt
ltfont color"red"gt
ltjspgetProperty name"userInfo"
property"propertyStatusMsg" /gt
lt/fontgt

lt-- Output form with submitted valid values --gt
ltform action"userinfo4.jsp" method"get"gt
lttablegt
lttrgt
lttdgtNamelt/tdgt
lttdgtltinput type"text" name"userName"
value"lt StringFormat.toHTMLString(u
serInfo.getUserName()) gt" gt
lt/tdgt
lt/trgt
lttrgt
lttdgtBirth Datelt/tdgt
lttdgtltinput type"text" name"birthDate"
value"lt StringFormat.toHTMLString(u
serInfo.getBirthDate()) gt" gt
lt/tdgt
lttdgt(Use format yyyy-mm-dd)lt/tdgt
lt/trgt

lttrgt
lttdgtEmail Addresslt/tdgt
lttdgtltinput type"text" name"emailAddr"
value"lt StringFormat.toHTMLString(u
serInfo.getEmailAddr()) gt" gt
lt/tdgt
lttdgt(Use format name_at_company.com)lt/tdgt
lt/trgt
lttrgt
lttdgtSexlt/tdgt
lttdgtltinput type"text" name"sex"
value"lt StringFormat.toHTMLString(u
serInfo.getSex()) gt" gt
lt/tdgt
lttdgt(Male or female)lt/tdgt
lt/trgt
lttrgt
lttdgtLucky numberlt/tdgt
lttdgtltinput type"text"
name"luckyNumber"

value"lt StringFormat.toHTMLString(userInfo.get
LuckyNumber()) gt"gt
lt/tdgt
lttdgt(A number between 1 and 100)lt/tdgt
lt/trgt
lttrgt
lttd colspan2gtltinput type"submit"gtlt/tdgt
lt/trgt
lt/tablegt
lt/formgt
lt/bodygt
lt/htmlgt

14
Checking off Checkboxes Dynamically

lt_at_ page language"java" contentType"text/html"
gt
lt_at_ page import"com.ora.jsp.util." gt
lthtmlgt
ltbody bgcolor"white"gt
ltform action"checkbox.jsp"gt
ltinput type"checkbox" name"fruits"
value"Apple"gtAppleltbrgt
ltinput type"checkbox" name"fruits"
value"Banana"gtBananaltbrgt
ltinput type"checkbox" name"fruits"
value"Orange"gtOrangeltbrgt
ltinput type"submit" value"Enter"gt
lt/formgt

lt
String picked request.getParameterValues("
fruits")
if (picked ! null picked.length ! 0)
gt
You picked the following fruits
ltformgt
ltinput type"checkbox" name"fruits"
value"Apple"
lt ArraySupport.contains(picked,
"Apple") ?
"checked" "" gt gtAppleltbrgt
ltinput type"checkbox" name"fruits"
value"Banana"
lt ArraySupport.contains(picked,
"Banana") ?
"checked" "" gt gtBananaltbrgt
ltinput type"checkbox" name"fruits"
value"Orange"
lt ArraySupport.contains(picked,
"Orange") ?
"checked" "" gt gtOrangeltbrgt
lt/formgt
lt gt
lt/bodygt
lt/htmlgt

16
Using more request Methods

lt_at_ page language"java" contentType"text/html"
gt
lthtmlgt
ltbody bgcolor"white"gt
The following information was received
ltulgt
ltligtRequest Method lt request.getMethod()
gt
ltligtRequest URI lt request.getRequestURI()
gt
ltligtRequest Protocol lt request.getProtocol(
) gt
ltligtServlet Path lt request.getServletPath()
gt
ltligtQuery String lt request.getQueryString()
gt
ltligtServer Name lt request.getServerName()
gt
ltligtServer Port lt request.getServerPort()
gt
ltligtRemote Address lt request.getRemoteAddr(
) gt
ltligtRemote Host lt request.getRemoteHost()
gt
ltligtBrowser Type lt request.getHeader("User-A
gent") gt
lt/ulgt
lt/bodygt
lt/htmlgt

17
Declaring Variables and Methods

Instance variables and methods can be declared by
using declaration element but this is not
recommended.
Instance variables may cause problem because
JSPServlet are multithreaded.

18
Using a Declaration element

lt_at_ page language"java" contentType"text/html"
gt
lthtmlgt
ltheadgt
lttitlegtA page with a counterlt/titlegt
lt/headgt
ltbody bgcolor"white"gt
lt!
int globalCounter 0
gt
This page has been visited lt
globalCounter gt times.
ltpgt
lt
int localCounter 0
gt
This counter never increases its value lt
localCounter gt
lt/bodygt
lt/htmlgt

You can also declare a method. Only harm is that
in that case JSP page will contain too much code
and may be problem to maintain. Better approach
is use JavaBeans and custom actions.

20
Method declaration and use

lt_at_ page language"java" contentType"text/html"
gt
lthtmlgt
ltbody bgcolor"white"gt
lt!
String randomColor()
java.util.Random random new
java.util.Random()
int red (int) (random.nextFloat() 255)
int green (int) (random.nextFloat()
255)
int blue (int) (random.nextFloat()
255)
return ""
Integer.toString(red, 16)
Integer.toString(green, 16)
Integer.toString(blue, 16)
gt

lth1gtRandom Colorlt/h1gt
lttable bgcolor"lt randomColor() gt" gt
lttrgtlttd width"100" height"100"gtnbsplt/tdgt
lt/trgt
lt/tablegt
lt/bodygt
lt/htmlgt

Sharing Data Between JSP Pages, Requests, and
Users

23
Passing Control and Data Between Pages

Model-View-Controller (MVC)
Pass control from one page to another.
Pass data from one page to another.
EXAMPLE USER INFO
Display the form for user input (presentation)
Validate the input (request processing and
business logic).
Display the result of the validation
(presentation).
Lets use a separate jsp page for each aspect.

24
How it will work

The userinfoinput.jsp page dislays an input form
The user submit the form to userinputvalidate.jsp
to validate the input.
This page will process the request using the
UserInfoBean and passes control (forwards) to
either the userinfoinput.jsp page (if the input
is invalid) or
the userinfovalid.jsp page ( if the input is
valid).
UserInfoBean represents the Model
userinputvalidate.jsp page is the controller
userinfoinput.jsp userinfovalid.jsp represents
the Views.

25
Passing control from one page to other

ltjspforward pageuserinfovalid.jsp /gt
This action stops processing one page and starts
processing the page specified by the page
attribute instead, called the target page. The
control never returns to the original page.
The target page has access to all the parameter
of the request. You can also add additional
parameters when you pass control to another page
by using one or more nested ltjspparamgt action
element.
ltjspforward pageuserinfovalid.jspgt
ltjspparam namemsg valueinvalid e-mail
address /gt
lt/jspforwardgt

The page attribute is interpreted relative to the
location of the current page if it does not start
with /.
page index.jsp //file in same directory
page ../foo/index.jsp //file in different
directory
page /foo/index.jsp //context relative path

27
Passing Data from one Page to another

The scope defines for how long the object is
available and whether its available only to one
user or to all application users.
Page Default scope. Object in this scope only
available to actions and scriptlets within one
page.)
RequestThis scope is for Objects that needs to
be available to all pages processing the same
request.
Session This scope is for Objects shared by
multiple requests by the same user
Application This scope is for Objects shared by
all users of the application.

ltjspuseBean iduserInfo scoperequest
class com.ora.jsp.beans.userinfo.UserInfoBean
/gt
If you want to perform an action only when the
bean is created, place the elements in the body
of the ltjspuseBeangt
ltjspuseBean iduserInfo scoperequest
class com.ora.jsp.beans.userinfo.UserInfoBean
gt
ltjspsetProperty nameuserInfo property
/gt
lt/jspuseBeangt

29
Putting it all togather (userinfoinput.jsp)