I have implemented a session bean to keep parameter values that will be used by the entire application.This is the simplest form of my session bean:

@Stateful
@Name("cart")
@Scope(SESSION)
public class Brtest implements BrtestI,Serializable{

 static final long serialVersionUID = 8722576722482084467L;

 @PersistenceContext(type=PersistenceContextType.EXTENDED)
 EntityManager em;

 public String getCart() {
 return "hello";
 }

 @Destroy
 @Remove
 public void destroy() {}

}

I have to inject an instance of the previous session bean in one of my backing beam following the dvd store example of the seam examples and this is my code:

@Stateful
@Name("testSession")
public class TestSessionManager extends TestSessionManager implements serialisable{

 @In(create=true) Brtest cart;

 @PersistenceContext(type=PersistenceContextType.EXTENDED)
 private EntityManager em;

 static final long serialVersionUID = -6536629890251170098L;

 @In
 protected FacesContext facesContext;

 protected void getValueFromSession(){
 cart.getCart();
 }

The exception thrown is this:

Caused by: javax.ejb.EJBTransactionRolledbackException: java.lang.IllegalArgumentException: could not set field value: testSession.cart
at org.jboss.ejb3.tx.Ejb3TxPolicy.handleInCallerTx(Ejb3TxPolicy.java:93)
at org.jboss.aspects.tx.TxPolicy.invokeInCallerTx(TxPolicy.java:130)
at org.jboss.aspects.tx.TxInterceptor$Required.invoke(TxInterceptor.java:195)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
at org.jboss.aspects.tx.TxPropagationInterceptor.invoke(TxPropagationInterceptor.java:76)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
at org.jboss.ejb3.stateful.StatefulInstanceInterceptor.invoke(StatefulInstanceInterceptor.java:83)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
at org.jboss.aspects.security.AuthenticationInterceptor.invoke(AuthenticationInterceptor.java:77)
at org.jboss.ejb3.security.Ejb3AuthenticationInterceptor.invoke(Ejb3AuthenticationInterceptor.java:102)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
at org.jboss.ejb3.ENCPropagationInterceptor.invoke(ENCPropagationInterceptor.java:47)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
at org.jboss.ejb3.asynchronous.AsynchronousInterceptor.invoke(AsynchronousInterceptor.java:106)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
at org.jboss.ejb3.stateful.StatefulContainer.localInvoke(StatefulContainer.java:203)
at org.jboss.ejb3.stateful.StatefulLocalProxy.invoke(StatefulLocalProxy.java:98)
at $Proxy341.getUsername(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.jboss.seam.util.Reflections.invoke(Reflections.java:20)
at org.jboss.seam.intercept.RootInvocationContext.proceed(RootInvocationContext.java:31)
at org.jboss.seam.intercept.ClientSideInterceptor$1.proceed(ClientSideInterceptor.java:72)
at org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:57)
at org.jboss.seam.interceptors.RemoveInterceptor.aroundInvoke(RemoveInterceptor.java:40)
at org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:69)
at org.jboss.seam.interceptors.SynchronizationInterceptor.aroundInvoke(SynchronizationInterceptor.java:31)
at org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:69)
at org.jboss.seam.intercept.RootInterceptor.invoke(RootInterceptor.java:103)
at org.jboss.seam.intercept.ClientSideInterceptor.invoke(ClientSideInterceptor.java:50)
at org.javassist.tmp.java.lang.Object_$$_javassist_290.getUsername(Object_$$_javassist_290.java)
... 73 more
Caused by: java.lang.IllegalArgumentException: could not set field value: testSession.cart
at org.jboss.seam.Component.setFieldValue(Component.java:1559)
at org.jboss.seam.Component.access$500(Component.java:135)
at org.jboss.seam.Component$BijectedField.set(Component.java:2285)
at org.jboss.seam.Component.injectAttributes(Component.java:1368)
at org.jboss.seam.Component.inject(Component.java:1195)
at org.jboss.seam.interceptors.BijectionInterceptor.aroundInvoke(BijectionInterceptor.java:46)
at org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:69)
at org.jboss.seam.interceptors.MethodContextInterceptor.aroundInvoke(MethodContextInterceptor.java:27)
at org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:69)
at org.jboss.seam.intercept.RootInterceptor.invoke(RootInterceptor.java:103)
at org.jboss.seam.intercept.SessionBeanInterceptor.aroundInvoke(SessionBeanInterceptor.java:53)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.jboss.ejb3.interceptor.InvocationContextImpl.proceed(InvocationContextImpl.java:118)
at org.jboss.ejb3.interceptor.EJB3InterceptorsInterceptor.invoke(EJB3InterceptorsInterceptor.java:63)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
at org.jboss.ejb3.entity.ExtendedPersistenceContextPropagationInterceptor.invoke(ExtendedPersistenceContextPropagationInterceptor.java:71)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
at org.jboss.ejb3.entity.TransactionScopedEntityManagerInterceptor.invoke(TransactionScopedEntityManagerInterceptor.java:54)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
at org.jboss.ejb3.AllowedOperationsInterceptor.invoke(AllowedOperationsInterceptor.java:46)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
at org.jboss.aspects.tx.TxPolicy.invokeInCallerTx(TxPolicy.java:126)
... 104 more
Caused by: java.lang.IllegalArgumentException: Could not set field value by reflection: TestSessionManager.cart on: twp.session.TestSessionManager with value: class org.javassist.tmp.java.lang.Object_$$_javassist_291
at org.jboss.seam.util.Reflections.set(Reflections.java:77)
at org.jboss.seam.Component.setFieldValue(Component.java:1555)
... 128 more
Caused by: java.lang.IllegalArgumentException
at sun.reflect.UnsafeObjectFieldAccessorImpl.set(UnsafeObjectFieldAccessorImpl.java:63)
at java.lang.reflect.Field.set(Field.java:656)
at org.jboss.seam.util.Reflections.set(Reflections.java:63)
... 129 more

Does anyone know what may cause this exception? Is there any additional configuration to be made (such as property files) in order a backing bean to communicate with the session bean?