Why am I getting a NoClassDefFoundError on HttpServletRequest that is pointing to ServletFileUpload?
file-upload, java, noclassdeffounderror, servlets, tomcat
Solution
All 3rd party webapp libraries like Commons FileUpload belong in `/WEB-INF/lib` of your webapp, not elsewhere. This exception can occur whenever you've placed it in `JRE/lib` or `JRE/lib/ext`.
And indeed, as Bozho mentions, you need to ensure as well that you haven't moved/copied/duplicated any servletcontainer-specific libraries (which should be left untouched in `Tomcat/lib`) around in different places of the classpath. But that should IMO not have resulted in this kind of exception. It's basically telling that the classloader which loaded the FileUpload API has totally no knowledge about the Servlet API.
If you read the Tomcat classloading HOW-TO, then you'll see that the libraries in `JRE/lib` and `JRE/lib/ext` are loaded by a different classloader (bootstrap) than the ones in `Tomcat/lib` (common) and `/WEB-INF/lib` (webapp). The bootstrap classloader has no knowledge about common and webapp libraries. It's the other way round. The common classloader has knowledge about the bootstrap classloader and the webapp classloader has knowledge about both. Since the Servlet API is normally loaded by the common classloader, this can only mean that the FileUpload API was loaded by the bootstrap classloader. And this is wrong :)
Problem
I recently started using JMeter to load test my webapp, locally on my pc. I have a jsp page for uploading images. The images are processed by my servlet. When I tried the process today, I got the following exception/error : ``` exception javax.servlet.ServletException: Servlet execution threw an exception root cause java.lang.NoClassDefFoundError: javax/servlet/http/HttpServletRequest org.apache.commons.fileupload.servlet.ServletFileUpload.isMultipartContent(ServletFileUpload.java:68) spyder.servlets.imageProcessing.ImageProcessingServlet.uploadEditedImagesToDB(ImageProcessingServlet.java:527) spyder.servlets.imageProcessing.ImageProcessingServlet.doPost(ImageProcessingServlet.java:153) javax.servlet.http.HttpServlet.service(HttpServlet.java:637) javax.servlet.http.HttpServlet.service(HttpServlet.java:717) ``` Here is the code from my servlet that the exception is referring to - ``` boolean isPart = ServletFileUpload.isMultipartContent(req); ``` ....and yes, I've put all the necessary `import` statements in the class. I can't recall making any changes to anything on my system that would cause this problem. This process has always run without any problems, so I don't understand what is causing it to fail like this now. Its rather coincidental, I think, that it is failing after I've been using JMeter...