Steps to Reproduce:
1. Log into OpenNMS
2. Go to /admin/provisioningGroups.htm
3. Click the 'Add New Group' button.
Reproducible: Always

Actual Results: Error and Stack trace
Expected Results: Nice front-end validation of forms with friendly error.

Long Description:
I happened to click the 'Add New Group' button on the aforementioned page without first entering anything into its associated text box. The result was a general 'The Web User Interface Has Experienced an Unexpected Error' message and a stack trace. The important part of the trace is:
'java.lang.IllegalArgumentException: Group name must not be null or the empty string'

Though it was a mistake on my part to click the button without entering any data and I could decipher the cause of the error, not everyone may be similarly capable at deducing the cause of the error.

My suggested is to add some front-end field validations--make it pretty with a nice red message and a red highlight around the required field. ; P

I'd be happy to look into the issue and create a patch but that would require me to become familiar with the underlying code aspects of the product, as I am currently just a user.

Your thoughts?

Additional information:
Web Server: Jetty
Java Version: 1.6.0_16 Sun Microsystems Inc.
Java Virtual Machine: 14.2-b01 Sun Microsystems Inc.
Operating System: Linux 2.6.28-11-server (amd64)
Servlet Container: jetty-6.1.9 (Servlet Spec 2.5)
User Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.3) Gecko/20090824 Firefox/3.5.3 (.NET CLR 3.5.30729)

Full Stack Trace:
java.lang.IllegalArgumentException: Group name must not be null or the empty string
at org.springframework.util.Assert.hasLength(Assert.java:136)
at org.opennms.web.svclayer.dao.support.DefaultManualProvisioningDao.checkGroupName(DefaultManualProvisioningDao.java:107)
at org.opennms.web.svclayer.dao.support.DefaultManualProvisioningDao.save(DefaultManualProvisioningDao.java:123)
at org.opennms.web.svclayer.support.DefaultManualProvisioningService.createProvisioningGroup(DefaultManualProvisioningService.java:193)
at org.opennms.web.controller.ProvisioningGroupsController.doAddGroup(ProvisioningGroupsController.java:123)
at org.opennms.web.controller.ProvisioningGroupsController.onSubmit(ProvisioningGroupsController.java:89)
at org.springframework.web.servlet.mvc.SimpleFormController.processFormSubmission(SimpleFormController.java:267)
at org.springframework.web.servlet.mvc.AbstractFormController.handleRequestInternal(AbstractFormController.java:265)
at org.springframework.web.servlet.mvc.AbstractController.handleRequest(AbstractController.java:153)
at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:48)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:858)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:792)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:476)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:441)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:487)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1093)
at org.extremecomponents.table.filter.AbstractExportFilter.doFilter(AbstractExportFilter.java:49)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1084)
at org.opennms.web.StoreRequestPropertiesFilter.doFilter(StoreRequestPropertiesFilter.java:71)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1084)
at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:265)
at org.acegisecurity.intercept.web.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:107)
at org.acegisecurity.intercept.web.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:72)
at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:275)
at org.acegisecurity.ui.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:166)
at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:275)
at org.acegisecurity.providers.anonymous.AnonymousProcessingFilter.doFilter(AnonymousProcessingFilter.java:125)
at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:275)
at org.acegisecurity.wrapper.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:81)
at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:275)
at org.acegisecurity.ui.basicauth.BasicProcessingFilter.doFilter(BasicProcessingFilter.java:173)
at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:275)
at org.acegisecurity.ui.AbstractProcessingFilter.doFilter(AbstractProcessingFilter.java:271)
at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:275)
at org.acegisecurity.ui.logout.LogoutFilter.doFilter(LogoutFilter.java:110)
at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:275)
at org.acegisecurity.context.HttpSessionContextIntegrationFilter.doFilter(HttpSessionContextIntegrationFilter.java:249)
at org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:275)
at org.acegisecurity.util.FilterChainProxy.doFilter(FilterChainProxy.java:149)
at org.acegisecurity.util.FilterToBeanProxy.doFilter(FilterToBeanProxy.java:98)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1084)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:360)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:726)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:405)
at org.mortbay.jetty.handler.HandlerCollection.handle(HandlerCollection.java:114)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:324)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:505)
at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:842)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:648)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:211)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:380)
at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:395)
at org.mortbay.thread.BoundedThreadPool$PoolThread.run(BoundedThreadPool.java:450)