JAVA SERVER PAGES CREATING DYNAMIC WEB PAGES USING JAVA

1
JAVA SERVER PAGESCREATING DYNAMIC WEB PAGES
USING JAVA

• James Faeldon
• CS 119 Enterprise Systems Programming

2
Overview

• Introduction to JSP
• Understanding the need for JSP
• Evaluating the benefits of JSP
• Installing JSP Files
• JSP Scripting Elements
• JSP Expressions
• JSP Scriplets
• JSP Declarations
• JSP Page Directive
• Understanding the purpose of the page directive
• Designating which classes are imported
• Specifying the MIME type of the page

3
Introduction to JSP

• Java Server Pages (JSP) technology enables you to
  mix regular, static HTML with dynamically
  generated content.

OrderConfirmation.jsp
4
Introduction to JSP

• Dynamic Pages can change in response to different
  context or conditions.

HTTP request parameters used as dynamic content
5
Servlets vs. JSP

• Servlets are good for data processing while JSP
  is good for presentation.
• Benefits of JSP
• It is easier to write and maintain the HTML
• You can use standard Web-site development tools
• You can divide up your development team

6
Reading 3 Parameters (Example)
SERVLET HTML code in JAVA
JSP JAVA code in HTML
ThreeParams.java
ThreeParams.jsp
7
Reading 3 Parameters (Example)
8
Servlets vs. JSP

• JSP doesnt provide any capabilities that
  couldnt be accomplished with Servlets.
• JSP documents are automatically translated into
  servlets behind the scenes.
• The issue is not the power of the technology, it
  is the convenience, productivity, and
  maintainability of one or the other.
• Choose the right tool for the job.

9
Installation of JSP files

• JSP Directories for Tomcat
• Main Location
• tomcat_install_dir/webapps/ROOT
• Corresponding URL
• http//localhost8080/SomeFile.jsp
• More Specific Location (Arbitrary Subdirectory)
• tomcat_install_dir/webapps/ROOT/SomeDirectory
• Corresponding URL
• http//localhost8080/SomeDirectory/SomeFile.jsp
  

10
Types of JSP Scripting Elements

• Expressions of the form lt Java Expression gt,
  which are evaluated and inserted into the
  servlets output.
• Scriptlets of the form lt Java Code gt, which are
  inserted into the servlets _jspService method
  (called by service).
• Declarations of the form lt! Field/Method
  Declaration gt, which are inserted into the body
  of the servlet class, outside any existing
  methods.

11
Using JSP Expressions

• A JSP expression is used to insert values
  directly into the output. It has the following
  form
• lt Java Expression gt
• Example
• Current time lt new java.util.Date() gt

12
Predefined Variables

• request, the HttpServletRequest.
• response, the HttpServletResponse.
• session, the HttpSession associated with the
  request (unless disabled with the session
  attribute of the page directive
• out, the Writer (a buffered version of type
  JspWriter) used to send output to the client.
• application, the ServletContext. This is a data
  structure shared by all servlets and JSP pages in
  the Web application and is good for storing
  shared data.
• Example
• Your hostname lt request.getRemoteHost() gt

13
Example JSP Expressions
Expressions.jsp
14
Example JSP Expressions
15
Writing JSP Scriplets

• If you want to do something more complex than
  output the value of a simple expression, JSP
  scriptlets let you insert arbitrary code. It has
  the following form
• lt Java Code gt
• Example
• lt
• String queryData request.getQueryString()
• out.println("Attached GET data " queryData)
  
• gt

16
Example JSP Scriplets
BgColor.jsp
17
Example JSP Scriplets
18
Another Example JSP Scriplets
DayWish.jsp
19
Another Example JSP Scriplets
20
Using JSP Declarations

• A JSP declaration lets you define methods or
  fields that get inserted into the main body of
  the servlet class. It has the following form
• lt! Field or Method Definition gt
• Example
• ltH1gtSome Headinglt/H1gt
• lt!
• private String randomHeading()
• return("ltH2gt" Math.random() "lt/H2gt")
• gt
• lt randomHeading() gt

21
Example JSP Declarations
AccesCounts.jsp
22
Example JSP Declarations
23
JSP Directive

• A JSP Directive affects the overall structure of
  the JSP page. It has the form
• lt_at_ directive attribute"value" gt
• lt_at_ directive attribute1"value1"
• attribute2"value2"
• ...
• attributeN"valueN" gt
• There are three main types of directives page,
  include and taglib.

24
The import Attribute

• The import attribute of the page directive lets
  you specify the packages that should be imported
  into the JSP page.
• lt_at_ page import"package.class" gt
• lt_at_ page import"package.class1,...,package.classN
  " gt
• Example
• lt_at_ page import"java.util." gt
• Date today lt new Date() gt

25
The contentType Attribute

• The contentType attribute sets the Content-Type
  response header, indicating the MIME type of the
  document being sent to the client.
• Use of the contentType attribute takes one of the
  following two forms.
• lt_at_ page contentType"MIME-Type" gt
• lt_at_ page contentType"MIME-Type
  charsetCharacter-Set" gt
• Example
• First Last Email Address
• James Gosling james_at_gosling.com
• Larry Brown larry_at_brown.com
• Steve Balmer steve_at_balmer.com
• Scott McNealy scott_at_mcnealy.com
• lt_at_ page contentType"application/vnd.ms-excel"
  gt
• lt-- There are tabs, not spaces, between columns.
  --gt

26
Example Conditionally Generating Excel
Spreadsheets
ApplesAndOranges.jsp
27
Example Conditionally Generating Excel
Spreadsheets
28
Strategies for invoking dynamic code in JSP

• Call Java code directly. Place all Java code in
  JSP page. Appropriate only for very small amounts
  of code.
• Call Java code indirectly. Develop separate
  utility classes. Insert into JSP page only the
  Java code needed to invoke the utility classes.
• Use beans. Develop separate utility classes
  structured as beans. Use jspuseBean,
  jspgetProperty, and jspsetProperty to invoke
  the code.
• Use the MVC architecture. Have a servlet respond
  to original request, look up data, and store
  results in beans.Forward to a JSP page to present
  results. JSP page uses beans.
• Use the JSP expression language. Use shorthand
  syntax to access and output object properties.
  Usually used in conjunction with beans and MVC.
• Use custom tags. Develop tag handler classes.
  Invoke the tag handlers with XML-like custom
  tags.

29
Tips

• Limit the amount of Java code that is in JSP
  pages. At the very least, use helper classes that
  are invoked from the JSP pages.
• Put all your classes in packages.
• Define most methods with separate Java classes,
  not JSP declarations.

30
Exercise

• Create a web page that will display the contents
  of the PERSON table in the owners database.
• You should be able to display the records in an
  HTML table or in an Excel spreadsheet.
• Note If your browser does not support displaying
  Excel spreadsheet a prompt will show just choose
  to open the file.