I have a probelm with passing an ArrayList to a Servlet. I use a session bean.
When my business method refers to a single object the everything works fine:

public util.CustDetails aut(int id) throws javax.ejb.FinderException {
        CustomerTblLocal cc = custHome.findByPrimaryKey(new Integer(id));
        return new util.CustDetails(cc.getCustomerNum(), cc.getCity(), cc.getName());
    }

When my business method refers to an ArrayList or Collection of objects then I get an error message

public java.util.ArrayList kkk(java.lang.String city) throws javax.ejb.FinderException,java.rmi.RemoteException {
        ArrayList list = null;
        Collection m = custHome.findByCity("Miami");
        Iterator i = m.iterator();
        while(i.hasNext()){
            CustomerTblLocal cc = (CustomerTblLocal)i.next();
            list.add(new util.CustDetails(cc.getCustomerNum(), cc.getName(),cc.getCity()));
        }
        return list;
    }

The error is seems to happen when I try to get the ArrayList in the servlet with the code:

java.util.ArrayList list = f.kkk("Miami");

Can you possibly figure out what is going on?

The server's log is :

[#|2005-06-18T13:13:54.582+0100|INFO|sun-appserver-pe8.1_02|javax.enterprise.system.container.ejb|_ThreadID=22;|
javax.ejb.EJBException
at com.sun.ejb.containers.BaseContainer.processSystemException(BaseContainer.java:2807)
at com.sun.ejb.containers.BaseContainer.completeNewTx(BaseContainer.java:2713)
at com.sun.ejb.containers.BaseContainer.postInvokeTx(BaseContainer.java:2521)
at com.sun.ejb.containers.BaseContainer.postInvoke(BaseContainer.java:819)
at com.sun.ejb.containers.EJBObjectInvocationHandler.invoke(EJBObjectInvocationHandler.java:137)
at $Proxy133.kkk(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 com.sun.corba.ee.impl.presentation.rmi.StubInvocationHandlerImpl.invoke(StubInvocationHandlerImpl.java:167)
at com.sun.corba.ee.impl.presentation.rmi.bcel.BCELStubBase.invoke(Unknown Source)
at ejb._FaceRemote_DynamicStub.kkk(_FaceRemote_DynamicStub.java)
at web.NewServlet.processRequest(NewServlet.java:42)
at web.NewServlet.doGet(NewServlet.java:63)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:747)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:860)
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.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:249)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAsPrivileged(Subject.java:517)
at org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:282)
at org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:165)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:257)
at org.apache.catalina.core.ApplicationFilterChain.access$000(ApplicationFilterChain.java:55)
at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:161)
at java.security.AccessController.doPrivileged(Native Method)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:263)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:551)
at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:225)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:173)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:551)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:161)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:551)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:132)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:551)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:933)
at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:185)
at com.sun.enterprise.web.connector.grizzly.ProcessorTask.process(ProcessorTask.java:653)
at com.sun.enterprise.web.connector.grizzly.ProcessorTask.process(ProcessorTask.java:534)
at com.sun.enterprise.web.connector.grizzly.ProcessorTask.doTask(ProcessorTask.java:403)
at com.sun.enterprise.web.connector.grizzly.WorkerThread.run(WorkerThread.java:55)
Caused by: java.lang.NullPointerException
at ejb.FaceBean.kkk(FaceBean.java:107)
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 com.sun.enterprise.security.SecurityUtil$2.run(SecurityUtil.java:153)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.enterprise.security.application.EJBSecurityManager.doAsPrivileged(EJBSecurityManager.java:950)
at com.sun.enterprise.security.SecurityUtil.invoke(SecurityUtil.java:158)
at com.sun.ejb.containers.EJBObjectInvocationHandler.invoke(EJBObjectInvocationHandler.java:128)
... 41 more
|#]

[#|2005-06-18T13:13:54.584+0100|SEVERE|sun-appserver-pe8.1_02|javax.enterprise.system.container.web|_ThreadID=22;|StandardWrapperValve[NewServlet]: Servlet.service() for servlet NewServlet threw exception
java.rmi.ServerException: RemoteException occurred in server thread; nested exception is:
java.rmi.RemoteException
at com.sun.corba.ee.impl.javax.rmi.CORBA.Util.wrapException(Util.java:657)
at javax.rmi.CORBA.Util.wrapException(Util.java:279)
at com.sun.corba.ee.impl.presentation.rmi.StubInvocationHandlerImpl.invoke(StubInvocationHandlerImpl.java:177)
at com.sun.corba.ee.impl.presentation.rmi.bcel.BCELStubBase.invoke(Unknown Source)
at ejb._FaceRemote_DynamicStub.kkk(_FaceRemote_DynamicStub.java)
at web.NewServlet.processRequest(NewServlet.java:42)
at web.NewServlet.doGet(NewServlet.java:63)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:747)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:860)
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.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:249)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAsPrivileged(Subject.java:517)
at org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:282)
at org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:165)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:257)
at org.apache.catalina.core.ApplicationFilterChain.access$000(ApplicationFilterChain.java:55)
at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:161)
at java.security.AccessController.doPrivileged(Native Method)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:263)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:551)
at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:225)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:173)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:551)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:161)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:551)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:132)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:551)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:933)
at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:185)
at com.sun.enterprise.web.connector.grizzly.ProcessorTask.process(ProcessorTask.java:653)
at com.sun.enterprise.web.connector.grizzly.ProcessorTask.process(ProcessorTask.java:534)
at com.sun.enterprise.web.connector.grizzly.ProcessorTask.doTask(ProcessorTask.java:403)
at com.sun.enterprise.web.connector.grizzly.WorkerThread.run(WorkerThread.java:55)
Caused by: java.rmi.RemoteException
|#]

ArrayList list = null;
...
   // lot of statement not setting list
...

return list;

But I thought that this line could do the job.

list.add(new util.CustDetails(cc.getCustomerNum(), cc.getName(),cc.getCity()));

It is true that it returns a null pointer exception.

But why something like this happens?

I think you need to initiate ArrayList list.
Hope this works fine.

It's ok now.
I just needed to check if the object added to the list is null.

if (object!=null){
    list.add(object);
}

This way it works.

Why haven't you something like:

return custHome.findCustomerDetailsByCity("Miami");

:)