Implicit Expression Language Objects In JSP:
The most useful feature of the JSTL Expression Language is the implicit
objects. It defines for accessing all kinds of application data. JSP developers
can directly use implicit objects in an EL expression. They do not need to write
extra code for using these objects. some of these objects allow the access to
variables held in the particular JSP scopes. All these objects map the
respective scope attribute names to their values.
The JSP Expression Language defines various
implicit objects:
| Objects Name |
Description |
| pageContext |
The instance of pageContext is
used to manipulate page attributes
access servletContext, session, request, response objects
|
| requestScope |
Maps request-scoped variable
names to their values |
| sessionScope |
Maps session-scoped variable
names to their values |
| applicationScope |
Maps application-scoped variable
names to their values |
| param |
Maps a request parameter name to
a single value |
| param values |
Maps a request parameter name to
an array of values |
| Header |
Maps a request header name to a
single value |
| headerValues |
Maps a request header name to an
array of values |
| cookie |
Maps a cookie name to a single
cookie |
| initParam |
Maps a context initialization
parameter name to a single value |
There are three types of implicit EL
objects:
- Maps for a single set of values, such as
request headers and cookies:
param, paramValues, header, headerValues, initParam, cookie - Maps for scoped variables in a particular
scope:
pageScope, requestScope, sessionScope, applicationScope - The page context:
pageContext
Example:
Using implicit EL Objects: In this example the user is asked to enter some
information and then that information is and
displayed along
with other information.
1.Index.jsp:
<html>
<body bgcolor="cyan">
<form action="imobjects2.jsp"
method="get">
<table border="2">
<tr><th>Using
Implicit Objects</th></tr>
<tr><td
colspan="2"><h3>pet shopping cart</h3></td></tr>
<tr><td>
Your Email
Id:<input type="text" name="email" size="30"
/> </td>
</tr>
<tr><td>Whats
Type of Pet do you have?
</td></tr>
<tr><td>Cat<input
type="checkbox" name="pettype"
value="cat"/>
</td></tr>
<tr><td>Dog<input
type="checkbox" name="pettype"
value="dog"/>
</td></tr>
<tr><td>Rabbit<input
type="checkbox" name="pettype"
value="rabbit"/>
</td></tr>
<tr><td>Goat<input
type="checkbox" name="pettype"
value="goat"/>
</td></tr>
<tr><td>Sheep<input
type="checkbox" name="pettype"
value="sheep"/>
</td></tr>
<tr><td>Horse<input
type="checkbox" name="pettype"
value="horse"/>
</td></tr>
</table>
<tr><td><input
type="submit" value="Submit"
></td><tr>
</table>
</form>
</body>
</html>
2.The impobject2.jsp:
<%@taglib uri="http://java.sun.com/jsp/jstl/core"
prefix="c"%>
<html>
<head>
<title>Using Implicit Objects</title>
</head>
<body bgcolor="pink"><table
border="2" align="center">
<tr><th>Using Implicit
Objects</th></tr></table>
<p><ul>
<li><b>Your Email Id Is:</b>${param.email}
<li><b>You have selected
pest:</b>
<c:forEach var="pet"
items="${paramValues.pettype}">
${pet}
</c:forEach>
<li><b>User-Agent Header:</b>
${header["User-agent"]}
<li><b>JSESSIONID Cookie
value:</b>${cookie.JSESSIONID.value}
<li><b>Server:</b>${pageContext.servletContext.serverInfo}
</ul>
</body>
</html>
OUTPUT:
1.Index.jsp:
![index.gif]()
2.The impobject2.jsp:
![import.gif]()