JSTL fmt:formatNumber
Solution 1
You're mixing oldschool scriptlets with EL and expecting that they share the same variable scope. This is not true. EL (those ${}
things) searches in respectively the page, request, session and application scopes for the first non-null
attribute matching the given name and returns it. It does not access the scriptlet local scope in any way.
Basically, to make
<%double distance=geo.getDistance(geo.getLatitude(), geo.getLongitude(), lat, lng);%>
available as ${distance}
, you need to set it in any of the desired EL scopes, e.g. the request scope
<%
double distance=geo.getDistance(geo.getLatitude(), geo.getLongitude(), lat, lng);
request.setAttribute("distance", distance);
%>
Once done that, then you can just use
<fmt:formatNumber pattern="0.0" value="${distance}"/>
without the need to massage with <c:set>
, by the way.
Note, a said, mixing scriptlets with EL is not the normal practice. You use the one or the other. In this particular case, that Java code belongs in a preprocessing servlet class.
Also note that your concrete problem is not specifically related to JSTL. You just pointed it a non-existent variable.
Solution 2
If you want to publish java variable to ${ExpressionLanguage}
you must add it to the context. There are application, session, request and page contexts. This is what happens in my test page.
- Using
<% ... %>
tags always indicates "heavy weight" java code, variables are not directly visible in JSTL code. - introduce java variable to JSTL context such as pagecontext. Now you can use
${xx}
EL variables in jsp code. - I did not put distance2 to a context, but using it through
<%= .. %>
embedded java scriptlet. Sometimes its just easiest to do this way. - You even can introduce
${EL}
- only variable back to heavy weight java side, usejsp:useBean
tag to create java variable. Then it can be seen in<%..%>
scriptlets. - I made a simple math expression inside
${distanceEL3}
value as an example. - For you information, if use Tomcat look at the
tomcat/work/Catalina/localhost/mywebapp/org/apache/jsp/test_jsp.java
file. You can see how variables are created like was written java file by hand.
test.jsp
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %><%@
taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt" %><%@page
contentType="text/plain; charset=UTF-8" pageEncoding="ISO-8859-1"
import="java.text.*"
%><%
double distance=1234.567;
double distance2=3456.789;
pageContext.setAttribute("distance", distance);
%>Test Results
<fmt:setLocale value="en_US" scope="page"/>
<c:set var="distanceEL" value="${distance}" />
distance=${distance}
fmt1=<fmt:formatNumber pattern="0.0" value="${distance}" />
fmt2=<fmt:formatNumber pattern="0.00" value="${distanceEL}" />
fmt3=<fmt:formatNumber pattern="0.0" value="1234.567" />
fmt4=<%= new DecimalFormat("0.0").format(distance) %>
<c:set var="distanceEL2" value="<%= distance2 %>" />
distance2=${distanceEL2}
fmt1=<fmt:formatNumber pattern="0.0" value="<%= distance2 %>" />
fmt2=<fmt:formatNumber pattern="0.00" value="${distanceEL2}" />
fmt4=<%= new DecimalFormat("0.0").format(distance2) %>
<c:set var="distanceEL3" value="${765.432-2.2}" />
<jsp:useBean id="distanceEL3" type="java.lang.Double" />
distance3=${distanceEL3}
fmt1=<fmt:formatNumber pattern="0.0" value="<%= distanceEL3 %>" />
fmt2=<fmt:formatNumber pattern="0.00" value="${distanceEL3}" />
fmt4=<%= new DecimalFormat("0.0").format(distanceEL3) %>
Chloe
Updated on July 09, 2022Comments
-
Chloe almost 2 years
How do I format a variable with <fmt:formatNumber> ? I'm learning JSTL and converting from old Struts tags. This doesn't work. It can't read the distance variable!
<%double distance=geo.getDistance(geo.getLatitude(), geo.getLongitude(), lat, lng);%> <c:set var="distanceEL" value="${distance}"/> ${distance}, <fmt:formatNumber pattern="0.0" value="${distance}"/>, <fmt:formatNumber pattern="0.0" value="${distanceEL}"/>, <fmt:formatNumber pattern="0.0" value="1234.567"/>, <%= new java.text.DecimalFormat("0.0").format(distance) %>
It displays as
, , , 1234.6, 19.3
I'm using JSTL 1.2. So far I'm not impressed.