JSP Action Elements
Lec - 37
JSP Journey
– directive elements ……………………….
– scripting elements
implicit
objects
•
•
•
•
JSP comments……………………………….
declarations …………………………………
expressions …………………………..……..
scriptlets………………………………..........
– action elements
• special JSP tags ………………………….….
JSP Action Elements
JSP Action Elements
• Format
– Expressed using XML syntax
• Opening tag
• Body
<jsp:actionElement attribute=“value” … >
body
• Closing tag
</jsp:actionElement >
– Empty tags without body
<jsp:actionElement attribute=“value” … />
JSP Action Elements cont.
• Purpose
– To work with JavaBeans
– To include pages at request time
– To forward request to another resource etc.
Some JSP Action Elements
• To work with JavaBeans
– <jsp:useBean />
– <jsp:setProperty />
– <jsp:getProperty />
• To include resources at request time
– <jsp:include />
• To forward request to anther JSP or Servlet
– <jsp:forward />
• To work with applets
– <jsp:plugin />
• And many more….
Working with JavaBeans
using JSP Action Elements
Working with JavaBeans
using JSP action elements
• JSP action elements also helps to work with JavaBeans
– <jsp:useBean />
• Makes a JavaBeans object available in a page
– <jsp:setProperty />
• Sets a JavaBeans property value
– <jsp:getProperty />
• Gets a JavaBeans property value
JSP useBean Action Element
• jsp:useBean is being equivalent to building an
object in scriptlet
<%
MyBean m = new MyBean();
%>
OR
<jsp:useBean id= “m” scope = “page” class=“vu.MyBean ”/>
JSP setProperty Action Element
• jsp:setProperty is being equivalent to following
code of scriptlet
<%
m.setName(“ali”);
%>
OR
<jsp:setProperty id = “m” property = “name”
value=“ali” />
JSP getProperty Action Element
• jsp:getProperty is being equivalent to following code
of scriptlet
<%
String name = m.getName();
out.println(name);
%>
OR
<jsp:getProperty id = “m” property= “name” />
Sharing Beans
&
Object Scopes
Understanding page Scope
first.jsp
request 1
second
.jsp
create
MyBean m = new MyBean();
m.setName(“ali”);
MyBean m
[name = ali]
Page Context
request 1
or request 2
third.jsp
Understanding request Scope
first.jsp
request 1
second
.jsp
create
MyBean m
[name = ali]
ServletRequest
request 1
third.jsp
request 2
fourth.jsp
Understanding session Scope
first.jsp
request 1
second
.jsp
create
MyBean m
[name = ali]
HttpSession
request 1
third.jsp
request 2
fourth.jsp
Understanding application Scope
first.jsp
request 1
second
.jsp
create
MyBean m
[name = ali]
ServletContext
request 1
third.jsp
request 2
fourth.jsp
Different Object Scopes
Most visible
Least visible
page
Objects may be accessed only within pages
where they are created
Different Object Scopes
Most visible
request
Least visible
page
Only within pages processing the request
in which they are created
Objects may be accessed only within pages
where they are created
Different Object Scopes
Most visible
Least visible
session
Only from pages belonging to same session
as the one in which they were created
request
Only within pages processing the request
in which they are created
page
Objects may be accessed only within pages
where they are created
Different Object Scopes
Most visible
Least visible
application
Within all pages belonging to same
application
session
Only from pages belonging to same session
as the one in which they were created
request
Only within pages processing the request
in which they are created
page
Objects may be accessed only within pages
where they are created
Object Scopes
session, request & page
Object Scopes
session vs. application
More JSP Action Elements
JSP include Action Element cont.
• jsp:include is being equivalent to following code of
scriptlet
<%
RequestDispatcher rd = request.getRequestDispatcher(“one.jsp”);
rd.include(request, response);
%>
OR
<jsp:include page = “one.jsp” flush= “true” />
JSP forward Action Element
• To forward request to another resource
• Format
<jsp:forward page=“one.jsp" />
• Works similar to following code of scriptlet
<%
RequestDispatcher rd = request.getRequestDispatcher(“one.jsp”);
rd.forward(request, response);
%>