Java Reference
In-Depth Information
Using EL Implicit Objects
Of the EL implicit objects listed in Table
3-3
,
applicationScope
,
pageScope
,
requestScope
, and
sessionScope
are meant for specifying scope. These are used to access scoped attributes, that is,
to access data from JavaBeans, maps, arrays, and lists that have been stored as attributes in any of
the four scopes: page, request, session, and application.
The other implicit objects listed in Table
3-3
are used to access request parameters, request
headers, cookies, context-initialization parameters, and
pageContext
objects. This section illustrates
the usage of some of the EL implicit objects.
Accessing Request Parameters
Listing 3-24 illustrates a simple form used to submit the request parameters through
form.jsp
.
Listing 3-24. form.jsp
1.<body>
2.<form action="books" method="post">
3.<input type="hidden" name="action" value="books"/>
4.<p>Book Title: <input type="text" name="bookTitle"></p>
5.<p>Author 1 Name: <input type="text" name="authorName"></p>
6.<p>Author 2 Name: <input type="text" name="authorName"></p>
7.
8.<input type = "submit"/>
9.</form>
10.</body>
In Listing 3-24, the
name
property of the
<input>
tag is the same:
authorName
.
Listing 3-25 illustrates the usage of the EL implicit objects
param
and
paramValues
to retrieve the
request parameter and display the result on the
result.jsp
page.
Listing 3-25. result.jsp
1.<p>Book Title: ${param.bookTitle}<br>
2.Author 1: ${paramValues.authorName[0]}<br>
3.Author 2: ${paramValues. authorName[1]}
4.</p>
Line 1
: This uses the EL implicit object
param
to get the
Book
title.
Line 2 to Line 3
: This code uses the EL implicit object
paramValues
to get the
Author 1
and
Author 2
names.
Accessing the Header
The EL implicit objects
header
and
headerValues
give you access to the header values that can be
obtained using the
request.getHeader()
and
request.getHeaders()
methods.
