HTTP Status 500 - java.lang.NoClassDefFoundError:

问题:

This question already has an answer here:

• How do I import the javax.servlet API in my Eclipse project? 14 answers

When I try to browse "localhost:8080" on myeclipse, I get the following error:

type Exception report

message java.lang.NoClassDefFoundError: Could not initialize class org.apache.jasper.el.ELContextImpl

description The server encountered an internal error that prevented it from fulfilling this request.

exception 

javax.servlet.ServletException: java.lang.NoClassDefFoundError: Could not initialize class org.apache.jasper.el.ELContextImpl
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:343)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:728)


root cause 

java.lang.NoClassDefFoundError: Could not initialize class org.apache.jasper.el.ELContextImpl
    org.apache.jasper.compiler.Validator$ValidateVisitor.prepareExpression(Validator.java:1568)
    org.apache.jasper.compiler.Validator$ValidateVisitor.visit(Validator.java:747)
    org.apache.jasper.compiler.Node$ELExpression.accept(Node.java:954)
    org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2376)
    org.apache.jasper.compiler.Node$Visitor.visitBody(Node.java:2428)
    org.apache.jasper.compiler.Node$Visitor.visit(Node.java:2434)
    org.apache.jasper.compiler.Node$Root.accept(Node.java:475)
    org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2376)
    org.apache.jasper.compiler.Validator.validateExDirectives(Validator.java:1795)
    org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:217)
    org.apache.jasper.compiler.Compiler.compile(Compiler.java:373)
    org.apache.jasper.compiler.Compiler.compile(Compiler.java:353)
    org.apache.jasper.compiler.Compiler.compile(Compiler.java:340)
    org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:646)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:357)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:728)

回答1:

Are you trying to run a Web app on Jetty server? The error NoClassDefFoundError means you do not have the jar file required to run that code.

Here is the stackoverflow question on the same issue.

org.apache.jasper.el.ELContextImpl cannot be cast to org.apache.jasper.runtime.ELContextImpl

If you are using the Eclipse IDE, I recommend you to download the Eclipse Jetty plugin

https://code.google.com/p/run-jetty-run/

or in your eclipse under help -> Market place -> enter 'jetty' or 'jetty plugin' then download run-jetty-run plugin

回答2:

In eclipse when there is a HTTP Status 500 - java.lang.NoClassDefFoundError in developing web application whether tomcat or jetty etc make sure to put the needed .jar files in the lib folder under the WEB-INF folder (/WEB-INF/lib) to solve the error

回答3:

I had the similar issue while trying to access localhost:8080. This is happening because tomcat is able to detect more than 1 copy of jasper.jar jsp-api,jasper-el.

The issue is due to conflicting jars.

Please remove the above jars from

1. java/jdk(version)/jre/lib/ext
2. Also remove the above jars from your web application lib directory.

Restart the tomcat and it will work fine.