Tomcat 构建错误：java.lang.NoClassDefFoundError

Question

The projet work fine in tomcat localhost but when I upload it in a remote tomcat I get this bug:/, I have the jar that contain the ImageReaderFactory class in classpath, I didn't understand what can be the problem, I cleared the /tomcat/work/Catalina/localhost folder but always the same bug: java.lang.NoClassDefFoundError

07-Oct-2019 23:06:25.584 SEVERE [http-apr-8080-exec-267] org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for servlet [UploadServlet] in context with path [/MyServer] threw exception [Servlet execution threw an exception] with root cause
 java.lang.NoClassDefFoundError: org/dcm4che3/imageio/codec/ImageReaderFactory
    at org.dcm4che3.imageio.plugins.dcm.DicomImageReader.setMetadata(DicomImageReader.java:794)
    at org.dcm4che3.imageio.plugins.dcm.DicomImageReader.readMetadata(DicomImageReader.java:713)
    at org.dcm4che3.imageio.plugins.dcm.DicomImageReader.read(DicomImageReader.java:452)
    at com.project.dicomserver.UploadServlet.getFrameIcon(UploadServlet.java:86)
    ....

Does anyone have any ideas?

image

Answer 1

There is a bunch of things that could be go wrong in your specific case. So answering with the best of my knowledge. Make amendments, by adding as much details as possible, to the question and we can help you further.

Every application in tomcat needs to have a specific folder structure. The folder structure is documented here . In short, war files must be deployed into $CATALINA_BASE/webapps/ directory.

So if your application is " myapp ", then there must be a $CATALINA_BASE/webapps/myapp directory.

Inside $CATALINA_BASE/webapps/myapp directory, we need to have WEB-INF . Not $CATALINA_BASE/webapps/myapp/WebContent/WEB-INF , but $CATALINA_BASE/webapps/myapp/WEB-INF . And the case matters.

If this is not how your application is deployed into a vanilla tomcat, it will not work properly. Read the official documentation

Now about your development environment, see whether your eclipse configurations have been modified. The Export As War options can be modified at multiple locations and all of them can have impact on the war file you have generated. When in doubt, I look at this link

Use a build tool like maven or gradle . These tools bring standards for compiling, archiving, testing and deploying applications and makes you worry less on environment related issues.