5 Jstl Meat If Tag Examples Inwards Jsp - Tutorial

<c:if>  or if tag of JSTL amount tag library inwards JSP is i of the most versatile together with useful tag. JSTL if tag allows you

to evidence for a condition, similar checking for a detail parameter inwards requestScope, sessionScope or pageScope. You tin too  check whatsoever parameter inwards asking parameters together with headers or tin banking concern gibe for a variable inwards JSP page using <c:if> tag. JSTL if tag helps a lot to bring down amount of Java code from JSP  page together with if used, along amongst facial expression linguistic communication JSTL amount tag library, tin take almost all Java code from JSP files. Earlier nosotros accept seen examples of JSTL foreach tag together with JSTL amount laid tag and this JSP JSTL tutorial is based on if tag of JSTL amount tag library. We will, run across how to work <core:if> tag within JSP files together with dissimilar instance of <core:if> tag to larn ourselves familiar amongst functionality together with ability offered yesteryear JSTL <c:if> tag. After seeing these examples of <core:if> tag along amongst facial expression language, You volition hold upwards amazed to see, how construct clean your JSP looks like.

What is <core:if> tag inwards JSTL together with JSP

<core:if> or <c:if> tag, based on prefix yous pick out on taglib declaration, is component of touchstone JSTL (Java Standard Tag libary). JSTL <core:if> tag evidence i status together with display or evaluate torso content alone if status is true. If evidence facial expression results inwards imitation 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 upwards evaluated if evidence status volition hold upwards true

</core:if>

test attribute contains a boolean facial expression which is used to evidence a status spell attribute var and scope tin hold upwards used to shop the lawsuit of test into a detail variable specified yesteryear var together with inwards a detail compass specified yesteryear scope. We volition run across instance of JSTL if tag for storing evidence lawsuit inwards instance section.

How to work JSTL IF tag inwards JSP

Here is a measurement yesteryear measurement conduct to work JSTL <core:if> tag within JSP file:

1) Download Java touchstone tag library or if yous are using Maven along amongst Eclipse or Netbeans IDE together with thus but import

dependency. Netbeans itself maintains laid of libraries including JSTL, Spring together with Struts, if yous download at that topographic point spider web package.

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

3) Import JSTL amount tag library inwards your JSP file yesteryear using <taglib> tag

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

Now yous are ready to work JSTL if tag inwards your JSP  file , but follow sytax of <c:if> tag together with yous volition hold upwards fine. Here prefix amount volition hold upwards used along amongst IF tag e.g. <core:if>.

JSTL if tag Examples inwards JSP

Here are to a greater extent than or less oft used examples of <c:if> tag for checking asking parameters, header values inwards JSP pages. This examples tin hold upwards best used to scream back syntax of JSTL if tag.

1) If status amongst asking parameter inwards JSP

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

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

</core:if>

This block of code inwards JSP volition alone execute, if asking contains a parameter called loan together with volition non display anything if asking parameter doesn't incorporate whatsoever parameter named loan.

2) If status amongst header parameter inwards JSP

This is similar to inwards a higher house instance of JSTL if tag. Only divergence is, instead of asking parameters straight off <core:if> will banking concern gibe headers for a detail parameter equally shown inwards below code:

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

Hello: ${header.cookie}

</core:if>

This JSTL instance checks if cookie is introduce inwards HTTP header together with display value of cookie if present.

3) How to banking concern gibe a detail variable inwards pageScope, requestScope together with sessionScope inwards JSTL if tag.

In this JSTL If tag example, nosotros accept position a variable loan inwards asking compass using <c:set> tag, which is to a greater extent than or less other JSTL tag. Later nosotros banking concern gibe for same variable using <c:if> tag.

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

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

Loan type is ${requestScope.loan}

</c:if>

4) How to banking concern gibe for a edible bean value inwards JSP if tag

This if tag volition alone hold upwards executed if type holding of loan object is "Personal Loan". This agency yous tin banking concern gibe for whatsoever holding of edible bean for detail value or null.

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

${loan}<br>

</c:if>

5) How to demo  result of <c:if> tag evidence inwards JSP

You tin export lawsuit of <c:if> tag status banking concern gibe using var together with scope. var is used to define cite of variable which holds lawsuit of if tag evaluation together with compass define compass of that variable. In next example, variable cookieTestResult volition concur lawsuit of if tag evaluation inwards 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 work JSTL <c:if> tag, let’ revise to a greater extent than or less of import things almost this tag inwards JSP.

1) While using if tag from JSTL amount library along amongst facial expression linguistic communication its skillful to recap implicit variables available to Expression Language or EL inwards JSP. They are pageContext, pageScope, requestScope, sessionScope together with applcationScope. They are self explanatory together with correspond Map holding request, session or application score attributes key is the cite of attribute together with value shape Map is value of that attribute. Apart from these v nosotros accept half-dozen to a greater extent than maps called param, paramValues, header, headerValues, cookie together with initParam. As cite advise they concur asking together with header parameters, cite together with values of cookie together with init parameters.

2)  Also scream back almost dot(.) and bracket([]) operator inwards JSP facial expression language; dot is used to larn holding from object together with bracket is used to larn elements from collections together with arrays.

That’s all on How to work <c:if> or JSTL If tag inwards JSP pages. For Java programmers, who sometime has added responsibleness to code JSP equally well, it’s hard to scream back syntax together with options of diverse JSTL tags. These <c:if> tag instance volition assist to rapidly scream back how to work JSTL if tag amongst total of its potential.

Further Learning
Spring Framework 5: Beginner to Guru
Java Web Fundamentals By Kevin Jones
JSP, Servlets together with JDBC for Beginners: Build a Database App