5 Jstl Centre If Tag Examples Inwards Jsp - Tutorial

<c:if>  or if tag of JSTL centre tag library inward JSP is ane of the most versatile too useful tag. JSTL if tag allows you

to examine for a condition, similar checking for a detail parameter inward requestScope, sessionScope or pageScope. You tin too  check whatever parameter inward asking parameters too headers or tin banking enterprise lucifer for a variable inward JSP page using <c:if> tag. JSTL if tag helps a lot to cut down sum of Java code from JSP  page too if used, along alongside human face linguistic communication JSTL centre tag library, tin take away almost all Java code from JSP files. Earlier nosotros bring seen examples of JSTL foreach tag too JSTL centre laid tag and this JSP JSTL tutorial is based on if tag of JSTL centre tag library. We will, run into how to exercise <core:if> tag within JSP files too dissimilar instance of <core:if> tag to larn ourselves familiar alongside functionality too ability offered past times JSTL <c:if> tag. After seeing these examples of <core:if> tag along alongside human face language, You volition hold out amazed to see, how build clean your JSP looks like.

What is <core:if> tag inward JSTL too JSP

<core:if> or <c:if> tag, based on prefix you lot select on taglib declaration, is component of measure JSTL (Java Standard Tag libary). JSTL <core:if> tag examine ane status too display or evaluate trunk content alone if status is true. If examine human face results inward fake than content of <core:if> body is non evaluated. Here is syntax of JSTL if tag:

<core:if test="boolean expression" var="variable" scope="scope">

body content alone hold out evaluated if examine status volition hold out true

</core:if>

test attribute contains a boolean human face which is used to examine a status spell attribute var and scope tin hold out used to shop the consequence of test into a detail variable specified past times var too inward a detail range specified past times scope. We volition run into instance of JSTL if tag for storing examine consequence inward instance section.

How to exercise JSTL IF tag inward JSP

Here is a mensuration past times mensuration direct to exercise JSTL <core:if> tag within JSP file:

1) Download Java measure tag library or if you lot are using Maven along alongside Eclipse or Netbeans IDE thence merely import

dependency. Netbeans itself maintains laid of libraries including JSTL, Spring too Struts, if you lot download at that spot spider web package.

2) Include jstl.jar inward application’s classpath. In spider web application, you lot should position JAR files on WEB-INF/lib folder, that folder is available on spider web application’s classpath.

3) Import JSTL centre tag library inward your JSP file past times using <taglib> tag

<%@ taglib prefix="core" uri="http://java.sun.com/jsp/jstl/core" %>

Now you lot are ready to exercise JSTL if tag inward your JSP  file , merely follow sytax of <c:if> tag too you lot volition hold out fine. Here prefix centre volition hold out used along alongside IF tag e.g. <core:if>.

JSTL if tag Examples inward JSP

Here are roughly oftentimes used examples of <c:if> tag for checking asking parameters, header values inward JSP pages. This examples tin hold out best used to recall syntax of JSTL if tag.

1) If status alongside asking parameter inward JSP

<core:if test="${param.loan != null}">

How to get: <%=request.getParameter("loan")%>

</core:if>

This block of code inward JSP volition alone execute, if asking contains a parameter called loan too volition non display anything if asking parameter doesn't comprise whatever parameter named loan.

2) If status alongside header parameter inward JSP

This is similar to to a higher house instance of JSTL if tag. Only divergence is, instead of asking parameters at in ane trial <core:if> will banking enterprise lucifer headers for a detail parameter equally shown inward below code:

<core:if test="${header.cookie == null}">

Hello: ${header.cookie}

</core:if>

This JSTL instance checks if cookie is acquaint inward HTTP header too display value of cookie if present.

3) How to banking enterprise lucifer a detail variable inward pageScope, requestScope too sessionScope inward JSTL if tag.

In this JSTL If tag example, nosotros bring position a variable loan inward asking range using <c:set> tag, which is roughly other JSTL tag. Later nosotros banking enterprise lucifer for same variable using <c:if> tag.

<c:set var="loan" value="Property Loan" scope="request" />

<c:if test="${requestScope.loan != nix }">

Loan type is ${requestScope.loan}

</c:if>

4) How to banking enterprise lucifer for a edible bean value inward JSP if tag

This if tag volition alone hold out executed if type holding of loan object is "Personal Loan". This agency you lot tin banking enterprise lucifer for whatever holding of edible bean for detail value or null.

<c:if test="${loan.type == 'Personal Loan'}">

${loan}<br>

</c:if>

5) How to present  result of <c:if> tag examine inward JSP

You tin export consequence of <c:if> tag status banking enterprise lucifer using var too scope. var is used to define advert of variable which holds consequence of if tag evaluation too range define range of that variable. In next example, variable cookieTestResult volition agree consequence of if tag evaluation inward asking scope.

<c:if test="${header.cookie == null}" var="cookieTestResult" scope="request">

Hello: ${header.cookie}

</c:if>

Result of Cookie Test:  <c:out value="${requestScope.cookieTestResult}"/>

Important points on JSTL <core:if> tag

Now nosotros know How to exercise JSTL <c:if> tag, let’ revise roughly of import things almost this tag inward JSP.

1) While using if tag from JSTL centre library along alongside human face linguistic communication its expert to recap implicit variables available to Expression Language or EL inward JSP. They are pageContext, pageScope, requestScope, sessionScope too applcationScope. They are self explanatory too correspond Map holding request, session or application score attributes key is the advert of attribute too value shape Map is value of that attribute. Apart from these five nosotros bring vi to a greater extent than maps called param, paramValues, header, headerValues, cookie too initParam. As advert advise they agree asking too header parameters, advert too values of cookie too init parameters.

2)  Also recall almost dot(.) and bracket([]) operator inward JSP human face language; dot is used to larn holding from object too bracket is used to larn elements from collections too arrays.

That’s all on How to exercise <c:if> or JSTL If tag inward JSP pages. For Java programmers, who sometime has added responsibleness to code JSP equally well, it’s hard to recall syntax too options of diverse JSTL tags. These <c:if> tag instance volition assistance to speedily recall how to exercise JSTL if tag alongside total of its potential.

Further Learning
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Java Web Fundamentals By Kevin Jones
JSP, Servlets too JDBC for Beginners: Build a Database App

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