NoClassDefFoundError动态Web项目Eclipse

Question

I have a Java web project which inside a .jar file as external Library added through Build Path -> Configure Build Path -> Add external jars . This jar it's been built using Maven's clean install argument and it uses org.apache.httpcomponents library added as dependency in his own pom.xml file.

Every time I try to invoke a certain url route to execute a Servlet which inside that jar invocation, I get this error java.lang.ClassNotFoundException: my.package.name.MyClass

The invocation is shown below:

import my.package.name.MyClass;
...
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
    ...
    MyClass mc = new MyClass();//<- java.lang.ClassNotFoundException
    ...
}

MyClass is a simple HTTP Client which has to send an HTTP request to an HTTP Server.

This is what I'm doing: Right click on the project -> Run on server -> [shows the index.jsp] -> Click on a button inside the index -> Exception

The stacktrace as requested:

java.lang.ClassNotFoundException: my.package.name.MyClass
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1720)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1571)
at my.servlet.package.name.doGet(MyServletClass.java:45)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:624)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:957)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:423)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1079)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:620)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:318)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)

Answer 1

If you've used mvn install to build the jar that the project is using, add it to your pom.xml instead of the build path.

The install part of maven will install it in your local repository and you can then include it in your pom.

I think you can also add the jar to be exported on the exports tab of the build path configuration, but I would use Maven to import the project from your local repo.