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JSTL - Tripod.com

Transcript JSTL - Tripod.com

JSTL
What is JSTL
• JSTL is an acronym for Java Standard Tag
Library
• JSTL contain tags that developer can use
in JSP pages
Tags in JSTL
• What tags are provided by JSTL
– Core tags
– Xml tags
– Sql tags
– Formatting tags
– Function tags
We will only do Core tags.
For other tags you need to know Servlets and
XML.
Core Tags
• The following tags are part of Core Tag
<c:set
<c:out
<c:if
test= “
<c:choose , <c:when , <c:otherwise
<c:forEach
<c:forTokens
<c:import
<c:url
<c:redirect
<c:param
How to use JSTL in JSP
• To use JSTL in JSP, you need to do some
configuration in JSP
Step1: download jstl.jar and standard.jar
Step2: copy both the files in WEB-INF
directory
Step3: Write jsp file that can use core tags.
Writing JSP file
• Make a HTML file jstl_ex.html and store it in the directory
\webapps\myJSPApps\proj1\
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<HTML>
<BODY>
<form method="post" action="greeting.jsp">
<input type="text" name="text1">
<input type="submit">
</form>
</BODY>
</HTML>
Writing JSP file
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<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<c:set var="s" value="${param.text1}" />
welcome <c:out value="${s}" />
Save the above file as greeting.jsp in webapps\MyJSPApps\proj1\
1. You can change prefix = “d”, in that case you have to use <d:set> or
<d:out> and so on.
2. The variable text1 comes from HTML file.
Explanation
<%@ taglib prefix="c"
uri="http://java.sun.com/jsp/jstl/core" %>
The line above means, include jstl library in jsp.
<c:set var="s" value="${param.text1}" />
This line means set the value of variable s to the
value of variable text1 from HTML file.
<c:out value="${s}" />
The line means, print the value of variable s.
Using <c:if>
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Write the following code in HTML file
<HTML>
<BODY>
<form method="post" action="greeting.jsp">
<select name="combo1">
<option value="Park">Park </option>
<option value="Chae">Chae </option>
</select>
<input type="submit">
</form>
</BODY>
</HTML>
Contd….
• Write the following code in JSP file
• <%@ taglib prefix="d"
uri="http://java.sun.com/jsp/jstl/core" %>
• <d:set var="s" value="${param.combo1}" />
• Welcome <d:out value="${s}" /><br>
• <d:if test="${s eq 'Park'}">
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<d:out value="Good Morning Mr.Park"/>
• </d:if>
• <d:if test="${s == 'Chae'}">
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<d:out value="How are you Mr. Chae"/>
• </d:if>
Explanation
• <d:if test="${s eq 'Park'}">
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<d:out value="Good Morning Mr.Park"/>
• </d:if>
• The above means, check the value of variable s.
If it is equal to 'park', then execute <d:out>.
• This tag is similar to if-then
• In the second <d:if> note that, I have used ==
instead of eq.
Using <c:choose>
Syntax:
• <c:choose>
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<c:when test=""> output1 </c:when>
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<c:otherwise> output2 </c:otherwise>
• </c:choose>
• Note that, we donot need <c:out> for
output here.
• This tag is similar to switch-case
Example
Write the following code in html file
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<HTML>
<BODY>
<form method="post" action="greeting.jsp">
<select name="combo1">
<option value="1">1 </option>
<option value="2">2 </option>
<option value="3">3 </option>
<option value="4">4 </option>
<option value="5">5 </option>
</select>
<input type="submit">
</form>
</BODY>
</HTML>
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Write the following code in jsp file
<%@ taglib prefix="d" uri="http://java.sun.com/jsp/jstl/core" %>
<d:set var="s" value="${param.combo1}" />
Today is
<d:choose>
<d:when test="${s == 1}"> Sunday </d:when>
<d:when test="${s == 2}"> Monday </d:when>
<d:when test="${s == 3}"> Tuesday </d:when>
<d:when test="${s == 4}"> Wednesday </d:when>
<d:when test="${s == 5}"> Thrusday</d:when>
<d:otherwise> Select between 1 and 5 </d:otherwise>
</d:choose>
<br><a href="jstl_ex.html"> go Back</a>
Using <c:forEach>
• This tag is same as for loop.
Syntax
• <c:forEach var="" start="" end="" step="" items=""
varStatus="">
• </c:forEach>
• var = "variable name"
• start = "start value"
• end = "ending value"
• step="increment or decrement value"
• varStatus = "" // i will explain thru example
• items = "" // i will explain thru example
Example
• Create a jsp file and write the following code
• <%@ taglib prefix="d"
uri="http://java.sun.com/jsp/jstl/core" %>
• <d:forEach var="n" begin="3" end="8">
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<d:out value="${n}"/>
• </d:forEach>
• The output is 3 4 5 6 7 8.
• If I write step=“2”, then output will be 3 5 7.
2nd Example of <c:forEach>
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<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%
String[] str = {"park", "chae", "won", "jung", "moon"};
pageContext.setAttribute("str1",str);
%>
<table border=1>
<tr><td>Index</td><td>Value</td><td>FirstValue</td><td>LastValue</td><td>Count
</td> </tr>
<c:forEach items="${str1}" varStatus="a">
<tr>
<td><c:out value="${a.index}"/></td>
<td><c:out value="${a.current}"/></td>
<td><c:out value="${a.first}"/></td>
<td><c:out value="${a.last}"/></td>
<td><c:out value="${a.count}"/> </td>
</tr>
</c:forEach>
</table>
Explanation
String[] str = {"park", "chae", "won", "jung", "moon"};
• The line above declares an array
pageContext.setAttribute("str1",str);
• This line gives page scope to str variable and stores the value of str in str1.
• That means str will be referred by str1 from now.
<c:forEach items="${str1}" varStatus="a">
• In this line, varStatus acts like an index for array str1.
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a.index returns the index
a.current returns the value of the element where a is pointing now.
a.first returns true if index = 0 or count = 1
a.last returns true if index = size of array-1 or count = size of array
a.count returns the position where a is pointing.
<c:forTokens> with delimiter
• <%@ taglib prefix="c"
uri="http://java.sun.com/jsp/jstl/core" %>
• <c:set var="s"
value="park,Gyeonggido,suwon,korea"/>
• <c:forTokens items="${s}" delims=","
var="a">
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<c:out value="${a}"/>
• </c:forTokens>
Using <c:import>
• <%@ taglib prefix="c"
uri="http://java.sun.com/jsp/jstl/core" %>
• This is conjoint.html
• <c:import url="conjoint.html" />
• welcome to this website
Using <c:redirect>
• <%@ taglib prefix="c"
uri="http://java.sun.com/jsp/jstl/core" %>
• <c:redirect
• url="ConjointCards.jsp" />
2nd Example of <c:redirect>
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Another Example of <c:redirect>
<c:redirect
url="ConjointCards.jsp" />
If you want you can also pass parameters to the
forwarded page
<c:redirect
url="ConjointCards.jsp" >
<c:param name="name1" value="SAM"/>
</c:redirect>

JSTL - Tripod.com

Transcript JSTL - Tripod.com

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