Jstl Tags
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used for displaying
the content on client after escaping XML and HTML markup tags
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This tag is useful
for setting up a variable value in a specified scope. It basically evaluates
an expression and sets the result in given variable
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It is used for
removing an attribute from a specified scope or from all scopes (page,
request, session and application). By default removes from all.
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<c: if>
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it is used for
testing conditions. There are two other optional attributes for this tag
which are var and scope, test is mandatory
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<c:choose>
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It’s like switch
statement in Java.
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<c:when>
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It’s like case
statement in Java.
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<c:otherwise>
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It works like default
attribute in switch-case statements.
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<c:catch>
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This tag is
used in exception handling.
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<c:import>
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it is used for
importing the content from another file/page to the current JSP page.
Attributes – var, URL and scope
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<c:forEach>
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it is used for executing
the same set of statements for a finite number of times
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<c:forTokens>
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It is used for
iteration but it only works with delimiter
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<c:param>
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This JSTL
tag is mostly used with <c:url> and <c:redirect> tags. It
adds parameter and their values to the output of these tags.
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<c:url>
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It converts a
relative url into a application context’s url
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<c:redirect>
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used for redirecting
the current page to another URL
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JSTL Functions
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This
function checks whether the given string is present in the input
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It checks whether
the provided string is present but it is not case sensitive.
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It is used for
finding out the start position of a string in the provided string. Function
returns -1 when string is not found in the input.
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It is used for
HTML/XML character escaping which means it treats html/xml tags as a string.
Similar to the escapeXml attribute of <c:out> tag.
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it concatenates the
strings with a given separator and returns the output string.
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fn:split()
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it splits a given
string into an array of substrings
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It is used for
computing the length of a string or to find out the number of elements in a
collection. It returns the length of the object.
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It checks the
specified string is a prefix of given string.
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It is
used for checking the suffix of a string. It checks whether the given string
ends with a particular string.
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used to get
substring from given string
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It is used for
getting a substring which is present in the input string before a specified
string.
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It gets a substring from input
which comes after a specified string.
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It removes spaces from beginning and end of a
string and function.
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it
converts string to uppercase string
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it
converts string to lower case string
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it search for a string in
the input and replace it with the provided string. It does case sensitive
processing.
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c:out
attributes
value :used to
assign value
escapeXml
:used to escape html/xml tags if it is set to true(by default),if
it is set to false it would not escape HTML/XML tags and the tags will work.
default :used to
give default value and it will be excuted if the value is null.
c:out tag with
value attribute
index.jsp
<%@ taglib uri="http://java.sun.com/jsp/jstl/core"
prefix="c"%>
<html>
<head>
<title>c:out
Tag </title>
</head>
<body>
<c:out value="${'<b>This
is a <c:out> Tag </b>'}"
/>
</body>
</html>
output
<b>This
is a <c:out> Tag </b>
c:out tag with
value and escapeXml attributes
index.jsp
<%@ taglib uri="http://java.sun.com/jsp/jstl/core"
prefix="c"%>
<html>
<head>
<title>c:out
Tag </title>
</head>
<body>
<c:out value="${'<b>This
is a <c:out> Tag </b>'}" escapeXml="false"/>
</body>
</html>
output
This is a Tag
c:out tag with
value and default attributes
index.jsp
<%@ taglib uri="http://java.sun.com/jsp/jstl/core"
prefix="c"%>
<html>
<head>
<title>c:out
Tag </title>
</head>
<body>
<%!String s=null; %>
<c:out value="${s}"
default="default message"/>
</body>
</html>
output
default
message
c:set
attributes:
var : used to
give a variable name
scope
: used to specify the scope like page, request, session, application.
value
: used to give the value to the variable or object
index.jsp
<%@ taglib uri="http://java.sun.com/jsp/jstl/core"
prefix="c"%>
<html>
<head>
<title>Example
of c:set tag</title>
</head>
<body>
<c:set var="name" scope="application"
value="java for job" />
<a href="process.jsp">Display</a>
</body>
</html>
process.jsp
<%@ taglib uri="http://java.sun.com/jsp/jstl/core"
prefix="c"%>
<c:out value="${name}" />
output
java
for job
c:remove
attribute
var :variable
name to be removed
scope:scope from which variable needs to be removed
index.jsp
<%@ taglib uri="http://java.sun.com/jsp/jstl/core"
prefix="c"%>
<html>
<head>
<title>c:remove
tag</title>
</head>
<body>
<c:set var="domain" scope="session"
value="www.javaforjob.com" />
<c:set var="developer" scope="session"
value="seshadri" />
<c:remove var="developer" />
<a href="process.jsp">process.jsp</a>
</body>
</html>
process.jsp
<%@ taglib uri="http://java.sun.com/jsp/jstl/core"
prefix="c" %>
<c:out value="${domain}"/><br>
<c:out value="${developer}" default="attribute is
removed hence no value"/>
output
www.javaforjob.com
attribute is removed hence no value
attribute is removed hence no value
c:if
attributes
test :used to
test the condition
var : Variable name in which the test
result would be stored.
scope
:
It defines the scope for storing the value. For
e.g. if it is set to session the stored var value can be accessed till the session is active.
index.jsp
<%@ taglib uri="http://java.sun.com/jsp/jstl/core"
prefix="c"%>
<html>
<head>
<title>JSTL
c:if Tag Example</title>
</head>
<body>
<c:set var="num" value="14"
/>
<c:if test="${num%2==0}" var="result"
scope="request">
<c:out value="${num} is a even
number" />
</c:if>
<c:if test="${num%2!=0}">
<c:out value="${num} is a odd
number" />
</c:if>
<a href="process.jsp">process.jsp</a>
</body>
</html>
output:
14
is a even number process.jsp
process.jsp
<%@ taglib uri="http://java.sun.com/jsp/jstl/core"
prefix="c" %>
<c:out value="${result}" default="result has no
value"/><br>
output:
true