Grailsflow procedure

Hi,
Am new to grailsflow.
I have created a sample flow to add two numbers by giving 3 process variables and 3 nodes.
Node1 is redirected to Node2 via an event and the Node2 is redirected to Node3 with different event name.
The type of the node1 is wait and created an action in the web-app/actions path to execute my groovy code.
Another two nodes are of activity. When i am trying to assign the action to a particular node so its getting assigned but when am
trying to save the process type we are getting exceptions

so can you plz suggest us on this exception

Integrity constraint violation FKDF9FD6A6928057B8 table: ACTION_STATEMENT in statement [delete from process_node_def where id=? and version=?]
Caused by: org.springframework.dao.DataIntegrityViolationException: could not delete: [com.jcatalog.grailsflow.model.definition.ProcessNodeDef#4]; nested exception is org.hibernate.exception.ConstraintViolationException: could not delete: [com.jcatalog.grailsflow.model.definition.ProcessNodeDef#4]
Class: ProcessDefController
At Line: [227]
Code Snippet:

org.codehaus.groovy.runtime.InvokerInvocationException: org.springframework.dao.DataIntegrityViolationException: could not delete: [com.jcatalog.grailsflow.model.definition.ProcessNodeDef#4]; nested exception is org.hibernate.exception.ConstraintViolationException: could not delete: [com.jcatalog.grailsflow.model.definition.ProcessNodeDef#4]

at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:92)

at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:234)

at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1062)

at groovy.lang.ExpandoMetaClass.invokeMethod(ExpandoMetaClass.java:926)

at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:893)

at groovy.lang.Closure.call(Closure.java:279)

at groovy.lang.Closure.call(Closure.java:274)

at org.codehaus.groovy.grails.web.servlet.mvc.SimpleGrailsControllerHelper.handleAction(SimpleGrailsControllerHelper.java:36

at org.codehaus.groovy.grails.web.servlet.mvc.SimpleGrailsControllerHelper.executeAction(SimpleGrailsControllerHelper.java:243)

at org.codehaus.groovy.grails.web.servlet.mvc.SimpleGrailsControllerHelper.handleURI(SimpleGrailsControllerHelper.java:203)

at org.codehaus.groovy.grails.web.servlet.mvc.SimpleGrailsControllerHelper.handleURI(SimpleGrailsControllerHelper.java:13

at org.codehaus.groovy.grails.web.servlet.mvc.SimpleGrailsController.handleRequest(SimpleGrailsController.java:8

at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:4

at org.codehaus.groovy.grails.web.servlet.GrailsDispatcherServlet.doDispatch(GrailsDispatcherServlet.java:264)

at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:807)

at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:571)

at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:511)

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:502)

at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1124)

at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:70)

at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1115)

at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:70)

at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1115)

at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:70)

at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1115)

at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:361)

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:766)

at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:417)

at org.mortbay.jetty.servlet.Dispatcher.forward(Dispatcher.java:334)

at org.mortbay.jetty.servlet.Dispatcher.forward(Dispatcher.java:126)

at org.codehaus.groovy.grails.web.util.WebUtils.forwardRequestForUrlMappingInfo(WebUtils.java:293)

at org.codehaus.groovy.grails.web.util.WebUtils.forwardRequestForUrlMappingInfo(WebUtils.java:269)

at org.codehaus.groovy.grails.web.util.WebUtils.forwardRequestForUrlMappingInfo(WebUtils.java:261)

at org.codehaus.groovy.grails.web.mapping.filter.UrlMappingsFilter.doFilterInternal(UrlMappingsFilter.java:181)

at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)

at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1115)

at org.codehaus.groovy.grails.web.sitemesh.GrailsPageFilter.obtainContent(GrailsPageFilter.java:221)

at org.codehaus.groovy.grails.web.sitemesh.GrailsPageFilter.doFilter(GrailsPageFilter.java:126)

at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1115)

at org.codehaus.groovy.grails.web.servlet.filter.GrailsReloadServletFilter.doFilterInternal(GrailsReloadServletFilter.java:101)

at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)

at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1115)

at org.codehaus.groovy.grails.web.servlet.mvc.GrailsWebRequestFilter.doFilterInternal(GrailsWebRequestFilter.java:65)

at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)

at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1115)

at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:96)

at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)

at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:236)

at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:167)

at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1115)

at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:361)

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:766)

at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:417)

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:534)

at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:879)

at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:741)

at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:213)

at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:403)

at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)

at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:522)

Caused by: org.springframework.dao.DataIntegrityViolationException: could not delete: [com.jcatalog.grailsflow.model.definition.ProcessNodeDef#4]; nested exception is org.hibernate.exception.ConstraintViolationException: could not delete: [com.jcatalog.grailsflow.model.definition.ProcessNodeDef#4]

at ProcessDefController$_closure6.doCall(ProcessDefController.groovy:227)

at ProcessDefController$_closure6.doCall(ProcessDefController.groovy)

Caused by: org.hibernate.exception.ConstraintViolationException: could not delete: [com.jcatalog.grailsflow.model.definition.ProcessNodeDef#4]

... 2 more

Caused by: java.sql.SQLException: Integrity constraint violation FKDF9FD6A6928057B8 table: ACTION_STATEMENT in statement [delete from process_node_def where id=? and version=?]

at org.hsqldb.jdbc.Util.throwError(Unknown Source)

at org.hsqldb.jdbc.jdbcPreparedStatement.executeUpdate(Unknown Source)

... 2 more

and send me the various steps to create a workflow with simple examples
like
ordering a coffee,buying a book,printing a message.