[RESOLVIDO]Erro ao persistir JPA Struts 2 object references an unsaved transient instance

Boa noite to ha um tempo batalhando com esse erro.

Se senhores poderem me ajudar
Eu cadastro a Disciplina na boa, mas quando tento cadastrar a dos Cursos eo formulario do curso tem uma lista de Disciplina da esse erro, as duas estão mapeadas.

package br.com.curso.beans;

import java.io.Serializable;


import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;

@NamedQueries({
		@NamedQuery(name = "getCurso.Discplina", query = "select c from Curso c inner join fetch c.disciplina where c.nome like ?1"),
		@NamedQuery(name = "getCurso.Prepara", query = "select c from Curso c inner join fetch c.disciplina")

})
@Entity
public class Curso implements Serializable {

	private static final long serialVersionUID = 1166401819028622455L;

	@Id
	@GeneratedValue
	private Long idCurso;

	private String nome;

	private String descricao;

	private int duracao;

	public Curso(String nome, String descricao, int duracao) {
		
		this.nome = nome;
		this.descricao = descricao;
		this.duracao = duracao;
	}

	public Curso() {

	}

	@ManyToOne(fetch = FetchType.LAZY)
	@JoinColumn(name = "idDisciplina")
	private Disciplina disciplina;

	public Disciplina getDisciplina() {
		return disciplina;
	}

	public void setDisciplina(Disciplina disciplina) {
		this.disciplina = disciplina;
	}

	public Long getIdCurso() {
		return idCurso;
	}

	public void setIdCurso(Long idCurso) {
		this.idCurso = idCurso;
	}

	public String getNome() {
		return nome;
	}

	public void setNome(String nome) {
		this.nome = nome;
	}

	public String getDescricao() {
		return descricao;
	}

	public void setDescricao(String descricao) {
		this.descricao = descricao;
	}

	public int getDuracao() {
		return duracao;
	}

	public void setDuracao(int duracao) {
		this.duracao = duracao;
	}

	
}

Disciplina

package br.com.curso.beans;

import java.util.HashSet;
import java.util.Set;
import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.OneToMany;

@NamedQueries({
		@NamedQuery(name = "getDisciplina", query = "select d from Disciplina d inner join fetch d.cursos as c where c.nome like ?1 "),
		@NamedQuery(name = "getDisciplina_Curso", query = "select d from Disciplina d inner join fetch d.cursos as c ") 
		
})
@Entity
public class Disciplina {

	@Id
	@GeneratedValue
	private Long idDisciplina;

	private String nome;

	@OneToMany(cascade=CascadeType.ALL, mappedBy = "disciplina")
	private Set<Curso> cursos = new HashSet<Curso>();
	
	public Set<Curso> getCursos() {
		return cursos;
	}

	public void setCursos(Set<Curso> cursos) {
		this.cursos = cursos;
	}

	public Long getIdDisciplina() {
		return idDisciplina;
	}

	public void setIdDisciplina(Long idDisciplina) {
		this.idDisciplina = idDisciplina;
	}

	public String getNome() {
		return nome;
	}

	public void setNome(String nome) {
		this.nome = nome;
	}

}

Action

	public String SaveCurso() {
		CursoImpl cursoImpl = new CursoImpl();
		curso.setDisciplina(disciplina);
		cursoImpl.adciona(curso);
		return "Save";
	}

IMPL

	public void adciona(Curso curso) {
		EntityManager em = (EntityManager) JPAUtil.getInstance()
		.createEntityManager();
		if(em.getTransaction().isActive()) {
			em.flush();
			em.persist(curso);
			em.getTransaction().commit();
			}else {
			em.getTransaction().begin();
			em.flush();
			em.persist(curso);
			em.getTransaction().commit();
			}

	}

org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: br.com.curso.beans.Curso.disciplina -> br.com.curso.beans.Disciplina at org.hibernate.engine.CascadingAction$9.noCascade(CascadingAction.java:387) at org.hibernate.engine.Cascade.cascade(Cascade.java:172) at org.hibernate.event.def.AbstractFlushingEventListener.cascadeOnFlush(AbstractFlushingEventListener.java:154) at org.hibernate.event.def.AbstractFlushingEventListener.prepareEntityFlushes(AbstractFlushingEventListener.java:145) at org.hibernate.event.def.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:88) at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:50) at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1216) at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:383) at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:133) at org.hibernate.ejb.TransactionImpl.commit(TransactionImpl.java:76) at br.com.curso.DAO.CursoImpl.adciona(CursoImpl.java:27) at br.com.curso.action.CursoAction.SaveCurso(CursoAction.java:37) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:404) at com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:267) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:229) at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:221) at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:86) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223) at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221) at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:150) at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:48) at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:86) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223) at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221) at com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:123) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223) at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221) at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:184) at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:86) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223) at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221) at com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:105) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223) at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221) at org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:83) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223) at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221) at org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:207) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223) at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221) at com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:74) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223) at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221) at com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:127) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223) at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221) at org.apache.struts2.interceptor.ProfilingActivationInterceptor.intercept(ProfilingActivationInterceptor.java:107) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223) at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221) at org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:206) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223) at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221) at com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:115) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223) at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221) at com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:143) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223) at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221) at com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:121) at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:86) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223) at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221) at org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:170) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223) at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221) at com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:123) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223) at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221) at com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:176) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223) at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221) at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:50) at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:504) at org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:422) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:244) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:161) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:108) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:558) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:379) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:243) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:259) at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:281) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at java.lang.Thread.run(Unknown Source)

Desde já obrigado

O problema estava na jsp que estava enviando valor nulo a Disciplina. e mudei a action.

<s:form action="cadastraCurso.action" validate="true">
<s:textfield name="curso.nome" label="Nome"></s:textfield>
<s:textfield name="curso.descricao" label="Decrição"></s:textfield>
<s:textfield name="curso.duracao" label="Duração"/>
<s:select label="Disciplina" name="curso.disciplina.idDisciplina" list="disciplinas" listValue="nome" listKey="idDisciplina"/>
<s:submit value="Gravar"
	public String SaveCurso() {
		CursoImpl cursoImpl = new CursoImpl();
		if(curso.getIdCurso()!=null){
			curso.setDisciplina(disciplina);
			cursoImpl.update(curso);
		}
		//curso.setDisciplina(disciplina);
		cursoImpl.adciona(curso);
		return "Save";
	}