Java Server Pages

1
Java Server Pages

• by Jon Pearce

2
JSP Documents

• JSP docs are XHTML Documents containing
• Fixed-Template Data FTD
• HTML Components
• XML markup
• JSP Components ltJSPgt

3
demo.jsp
lt?xml version 1.0?gtlt!DOCTYPE html PUBLIC
".../xhtml1-strict.dtd"gtlthtml xmlns
"http//www.w3.org/1999/xhtml"gtltheadgt lttitlegt
Demo lt/titlegt lt/headgtltbodygt FTD ltJSPgt FTD
ltJSPgt FTD ltJSPgt...lt/bodygtlt/htmlgt
4
JSP Components ltJSPgt

• Scriptlets
• lt, lt--, lt, lt! ... gt
• Directives
• lt_at_ directive gt
• Actions
• ltjsp actiongt ... lt/jspactiongt
• ltmyNSactiongt ... lt/myNSactiongt

5
JSP Facts

• The container compiles a JSP to a servlet the
  first time it is served.
• Use JSPs when ratio of FTD to Dynamic Content is
  high
• JSPs decouple design from programming
• JSP HTML containing Java
• Servlet Java containing HTML
• JSPs replace views

6
JSP Compilation
7
Scriptlets

• lt (partial) statement gt
• lt-- comment --gt
• lt! declaration gt
• lt expression gt

8
Examples of Scripting Components

• lt! int counter 0 gt
• counter lt counter gt
• lt if (counter gt 5) counter 0 gtHTMLlt
  else counter gtALTERNATIVE HTML
• lt-- don't read this --gt

9
Implicit Objects

• Application Scope
• application
• Session Scope
• session
• Request Scope
• request
• Page Scope
• response, out, page, pageContext

10
Example
lt String name request.getParameter("name")
if (name ! null) gt ltpgt Hello lt name
gt lt/pgtlt else gt ltpgt Hello John Doe
lt/pgtlt gt
11
javax.servlet.jsp
12
The JSP to Servlet Translation
public class MyJSP implements HttpJspPage //
... public void _jspService(HttpServletRequest
request, HttpServletResponse response) throws
IOException, ServletException JspFactory
factory JspFactory.getDefaultFactory()
PageContext pageContext factory.getPageContext
(...) HttpSession session
pageContext.getSession() JspWriter out
pageContext.getOut() Object page this
try // body of translated JSP
goes here ... catch (Exception e)
out.clear() pageContext.handlePageE
xception(e) finally
out.close() factory.releasePageContext(p
ageContext)
13
Examples

• clock.jsp
• lt new java.util.Date() gt
• scriptTest.jsp
• Pallindrome Tester
• beanTest.jsp
• various counters
• personView.jsp

14
Standard Actions

• ltjspactiongt ... lt/jspactiongt
• include
• forward
• plugin
• param
• useBean
• setProperty
• getProperty

15
Directives

• lt_at_ include ... gt
• lt_at_ taglib ... gt
• lt_at_ page ... gt
• lt_at_ page errorPage "foo.jsp" gt
• lt_at_ page session "true" gt
• lt_at_ page language "java" gt
• lt_at_ page extends "java.awt.Frame" gt
• lt_at_ page import "java.util." gt

16
Include Directive

• lt_at_ include file "banner.html" gt

17
Include Directive vs. Action

• ltjspinclude page "foo.jsp" flush "true" /gt
• foo.html included after each change
• lt_at_ include file "foo.jsp" gt
• foo.html included once at compile time
• Static (html) or dynamic (jsp) files can be
  included

18
forward

• ltjspforward page "foo.jsp"gt ltjspparam
  name "date" value "lt new Date() gt"
  /gtlt/jspforwardgt

19
useBean

• ltjspuseBean id"cart" scope"session" class
  "CartBean" /gt
• Accessing Bean Properties
• lt cart.getTotal() gt
• ltjspgetProperty name "cart" property "total"
  /gt
• Setting Bean Properties
• lt cart.setTotal(200) gt
• ltjspsetProperty name "cart" property "total"
  value "200" /gt

20
Example
ltjspuseBean id "helper" scope "session"
class "ViewHelper" /gt lt String command
request.getParameter("cmmd")String content
helper.execute(command)gt ltpgt result lt
content gt lt/pgt
21
Custom Tag Libraries