We've been using DisplayTag for awhile now without any problems, but recently, we had a wonky hdd and so we had to restore some of the stuff on there. Unfortunately, DisplayTag broke and stops everything else when called: Will return with the following error: java.lang.NullPointerException java.lang.Class.forName0(Native Method) java.lang.Class.forName(Class.java:164) org.displaytag.properties.TableProperties.getClassProperty(TableProperties.java:759) org.displaytag.properties.TableProperties.getClassPropertyInstance(TableProperties.java:776) org.displaytag.properties.TableProperties.getRequestHelperFactoryInstance(TableProperties.java:714) org.displaytag.tags.TableTag.initParameters(TableTag.java:715) org.displaytag.tags.TableTag.doStartTag(TableTag.java:600) org.apache.jsp.misc.key_002dtable_jsp._jspService(key_002dtable_jsp.java:113) org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:94) javax.servlet.http.HttpServlet.service(HttpServlet.java:802) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:324) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236) javax.servlet.http.HttpServlet.service(HttpServlet.java:802) sun.reflect.GeneratedMethodAccessor36.invoke(Unknown Source) sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) java.lang.reflect.Method.invoke(Method.java:585) org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:243) java.security.AccessController.doPrivileged(Native Method) javax.security.auth.Subject.doAsPrivileged(Subject.java:517) org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:272) org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:161) I'm not quite familiar with Apache Tomcat and Java but I suspect that it has to do with a catalina's security policy. I'm hoping that someone could either confirm this or help point me in the right direction. We're currently on Tomcat 5.
first check for classpath incompatibilities. Clean your web-app dir and deploy afresh