java.lang.NoClassDefFoundError

Question

Everything was working just fine but now I can no longer run my application. For some reason javax.* is not being found yet in Eclipse the imports are fine...

exception 

javax.servlet.ServletException: Error allocating a servlet instance
 org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
 org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
 org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:857)
 org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
 org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
 java.lang.Thread.run(Thread.java:619)


root cause 

java.lang.NoClassDefFoundError: javax/servlet/http/HttpServlet
 java.lang.ClassLoader.defineClass1(Native Method)
 java.lang.ClassLoader.defineClassCond(ClassLoader.java:632)
 java.lang.ClassLoader.defineClass(ClassLoader.java:616)
 java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
 java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
 java.net.URLClassLoader.access$000(URLClassLoader.java:58)
 java.net.URLClassLoader$1.run(URLClassLoader.java:197)
 java.security.AccessController.doPrivileged(Native Method)
 java.net.URLClassLoader.findClass(URLClassLoader.java:190)
 java.lang.ClassLoader.loadClass(ClassLoader.java:307)
 sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
 java.lang.ClassLoader.loadClass(ClassLoader.java:248)
 org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1560)
 org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1491)
 org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
 org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
 org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:857)
 org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
 org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
 java.lang.Thread.run(Thread.java:619)


root cause 

java.lang.ClassNotFoundException: javax.servlet.http.HttpServlet
 java.net.URLClassLoader$1.run(URLClassLoader.java:202)
 java.security.AccessController.doPrivileged(Native Method)
 java.net.URLClassLoader.findClass(URLClassLoader.java:190)
 java.lang.ClassLoader.loadClass(ClassLoader.java:307)
 sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
 java.lang.ClassLoader.loadClass(ClassLoader.java:248)
 java.lang.ClassLoader.defineClass1(Native Method)
 java.lang.ClassLoader.defineClassCond(ClassLoader.java:632)
 java.lang.ClassLoader.defineClass(ClassLoader.java:616)
 java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
 java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
 java.net.URLClassLoader.access$000(URLClassLoader.java:58)
 java.net.URLClassLoader$1.run(URLClassLoader.java:197)
 java.security.AccessController.doPrivileged(Native Method)
 java.net.URLClassLoader.findClass(URLClassLoader.java:190)
 java.lang.ClassLoader.loadClass(ClassLoader.java:307)
 sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
 java.lang.ClassLoader.loadClass(ClassLoader.java:248)
 org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1560)
 org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1491)
 org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
 org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
 org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:857)
 org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
 org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
 java.lang.Thread.run(Thread.java:619)

Answer 1

You normally have servlet-api.jar in Apache Tomcat "Server Runtime" library.

When you define Server Runtime in Elcipse, this library is defined and will include link to servet-api.jar in Tomcat.

When you create dynamic web project it should have this library defined in Java Build Path. Check if your project has this build path.

Answer 2

Add the servlet-api.jar to the project classpath. Servlet containers have this jar bundled, so no need to add it to lib .

Answer 3

just copy the servlet-api jar, and paste into your webapps lib directory. and then select your project in eclipse -> mouse right click -> properties -> java build path -> select tab "order and export" -> select All -> finish.

now just runt your application using eclipse. i hope it will works fine. still problem is there, then tell me, i will tell you another solution