If there is a location in your development process: java.lang.NoClassDefFoundError: javax / servlet / ServletInputStream fileupload.FileUpload.doPost (FileUpload.java:36) javax.servlet.http.HttpServlet.service (HttpServlet.java:717) javax .Servlet.http.httpservlet.service (httpservlet.java:810) Like this error, please see my answer. First, you have to check if there is any J2EE.jar in your classpath, you go to download a Tomcat, then copy Tomcat_path / common / lib / servlet-api.jar, put it in your Your_Project / Web-INF In / lib, this is okay. Third, if you can't find it, please put this servlet-api.jar in, JDK_PATH / JRE / LIB / EXT, it is OK.
