JSTL breaks on GoogleAppEngine's development server, but works on remote server_问答_开发者

As the title says, my JSTL tags don't work on my development server, but do work on Google's actual server.

I simplified the code to the bare bone to make sure there wasn't anything wrong with the code, so here's what I've got.

JSP

<%@ page language=开发者_运维百科"java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1" isELIgnored="false"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Page Title</title>
</head>
<body>
    <c:choose>
        <c:when test="${2+2==4}">sum works</c:when>
        <c:otherwise>sum doesn't work</c:otherwise>
    </c:choose>
</body>

My configuration is as follows (which I think is correct and which works on Google's server): I'm using

Eclipse IDE
Servlet 2.5
No jstl jar added to WEB-INF\lib
No tld added anywhere
No taglib reference

on web.xml

However, I have also tried a number of combinations of the following and none of them worked:

jstl-1.2.jar added to the build path
c.tld added to WEB-INF
taglib reference added to web.xml

Error is below:

HTTP ERROR 500
Problem accessing /index.html. Reason: 

    javax/servlet/jsp/tagext/TagSupport

Caused by:

java.lang.NoClassDefFoundError: javax/servlet/jsp/tagext/TagSupport
    at java.lang.ClassLoader.findBootstrapClass(Native Method)
    at java.lang.ClassLoader.findBootstrapClassOrNull(ClassLoader.java:927)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:298)
    at com.google.appengine.tools.development.DevAppServerClassLoader.loadClass(DevAppServerClassLoader.java:87)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClassCond(ClassLoader.java:632)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:616)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
    at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
    at com.google.appengine.tools.development.DevAppServerClassLoader.loadClass(DevAppServerClassLoader.java:87)
         ...

Strangely, though, <c:out value="${blah}"/> works both on the development and remote servers. other core tags don't work. If I try to add fmt tags, they don't work as well.

Any ideas?

You need to drop JSTL JAR in /WEB-INF/lib or at least in the /lib folder of the servletcontainer which you're using on local development.

You should not extract the JAR and clutter the webapp with loose TLD files and also not reference it anywhere in web.xml. Undo everything if you have done it. You should also not have the need to manually add it to Eclipse build path. Just dropping in /WEB-INF/lib folder ought to be enough.