java.lang.NoClassDefFoundError: javax/el/ELException
在maven中配置以下依赖：
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>
在resin-3.0.28中运行，报以下错误：
Servlet.service() for servlet jsp threw exception
java.lang.NoClassDefFoundError: javax/el/ELException
原因是容器不支持JSTL1.2，换成以下依赖就好了：
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
<version>1.1.2</version>
</dependency>
Tomcat中也有同样的问题
Tomcat6 JSP2.1 / Servlet2.5 / JSTL2.0
Tomcat5 JSP2.0 / Servlet2.4 / JSTL1.1
Tomcat4 JSP1.2 / Servlet2.3 / JSTL1.0
resin-3.0.28 JSP2.0 / Servlet2.4 / JSTL1.1
Tomcat5与Tomcat6的EL冲突，JSTL的版本问题
Servlet.service() for servlet jsp threw exception
java.lang.NoClassDefFoundError: javax/el/ELException
at java.lang.Class.getDeclaredMethods0(Native Method)
at java.lang.Class.privateGetDeclaredMethods(Class.java:2365)
at java.lang.Class.getDeclaredMethods(Class.java:1763)
at java.beans.Introspector$1.run(Introspector.java:1259)
at java.security.AccessController.doPrivileged(Native Method)
at java.beans.Introspector.getPublicDeclaredMethods(Introspector.java:1257)
at java.beans.Introspector.getTargetMethodInfo(Introspector.java:1125)
at java.beans.Introspector.getBeanInfo(Introspector.java:383)
at java.beans.Introspector.getBeanInfo(Introspector.java:155)
at java.beans.Introspector.getBeanInfo(Introspector.java:216)
at java.beans.Introspector.<init>(Introspector.java:364)
at java.beans.Introspector.getBeanInfo(Introspector.java:155)
at org.apache.jasper.compiler.Generator$TagHandlerInfo.<init>(Generator.java:3673)
at org.apache.jasper.compiler.Generator$GenerateVisitor.getTagHandlerInfo(Generator.java:2092)
at org.apache.jasper.compiler.Generator$GenerateVisitor.visit(Generator.java:1573)
at org.apache.jasper.compiler.Node$CustomTag.accept(Node.java:1441)
at org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2163)
at org.apache.jasper.compiler.Node$Visitor.visitBody(Node.java:2213)
at org.apache.jasper.compiler.Node$Visitor.visit(Node.java:2219)
这个问题应该是出在JSTL的支持上，通过查看，原来系统使用了JSTL1.2。
JSTL1.2
The JSTL 1.2 Maintenace Release aligns with the Unified Expression Language (EL) that is being delivered as part of the JavaServer Pages (JSP) 2.1 specification。JSTL 1.2 is part of the Java EE 5 platform. （from http://java.sun.com/products/jsp/jstl/）
JSTL1.1
Jakarta Taglibs hosts the Standard Taglib 1.1, an implementation of the JSP Standard Tag Library (JSTL), version 1.1, which was developed under the Java Community Process.
NOTE: Standard-1.1 (JSTL 1.1) requires a JSP container that supports the Java Servlet 2.4 and JavaServer Pages 2.0 specifications. Jakarta Tomcat 5 supports the new specifications. The Standard-1.1 taglib has been tested with Tomcat 5.0.3.
JSTL1.0
Standard-1.0 (implementation of the JSTL 1.0 specification) requires a JSP container that supports the Java Servlet 2.3 and JavaServer Pages 1.2 specifications. Jakarta Tomcat 4 supports these specifications. The Standard 1.0 taglib has been tested with Tomcat 4.1.24. (from http://jakarta.apache.org/taglibs/doc/standard-doc/intro.html)
Tomcat6 实现了servlet 2.5 和JSP2.1的规范，可以支持JSTL1.2；
而Tomcat5实现了 servlet 2.4 和JSP2.0的规范，只能支持JSTL1.1
所以，只要使用JSTL1.1(standard-1.1.jar和jstl-1.1.jar)替换JSTL1.2（jstl-1.2.jar）即可在Tomcat5下正常运行！
另外，web.xml必须指定使用servlet 2.4 和JSP2.0的规范：
<web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">