how do client get data packet returned from EJB method (public List getResultset(String sql)) ?

hecity 2003-11-23 06:14:42

Hi,
where I define one method in Entity bean which return query result,I test it in Entity bean body,it can get right return.But from client ,I can not get returned data. What is the reason for that?
java.lang.NullPointerException
void com.evermind.server.rmi.RMIConnection.EXCEPTION_ORIGINATES_FROM_THE_REMOTE_SERVER(java.lang.Throwable)
RMIConnection.java:1558
java.lang.Object com.evermind.server.rmi.RMIConnection.invokeMethod(com.evermind.server.rmi.RMIContext, long, long, java.lang.reflect.Method, java.lang.Object[])
RMIConnection.java:1511
java.lang.Object com.evermind.server.rmi.RemoteInvocationHandler.invoke(java.lang.Object, java.lang.reflect.Method, java.lang.Object[])
RemoteInvocationHandler.java:55
java.lang.Object com.evermind.server.rmi.RecoverableRemoteInvocationHandler.invoke(java.lang.Object, java.lang.reflect.Method, java.lang.Object[])
RecoverableRemoteInvocationHandler.java:22
java.util.List __Proxy1.getResultset(java.lang.String)
void Samplebbs_live.Tb_userClient.main(java.lang.String[])
Tb_userClient.java:84
Entity Bean:
public List getResultset(String sql)
{
List list = new ArrayList();
try
{
dbconn = getConnection();
st = dbconn.createStatement();
rs = st.executeQuery(sql);
ResultSetMetaData mtdata = rs.getMetaData();
if (rs==null)
{
System.out.println("null data");
return Collections.EMPTY_LIST;
}
int col = mtdata.getColumnCount();
while (rs.next())
{
map = new HashMap(col);
for (int i=1;i<=col;i++)
{
map.put(mtdata.getColumnName(i),rs.getString(i));
}
list.add(map);
}
dbclose(st,rs,dbconn);
for (int j=0;j<list.size();j++)
{
Map m = new HashMap(col);
m = (Map)list.get(j);
System.out.println(j);
System.out.println((String)m.get("mailaddr"));
}
}
catch (Exception se)
{
se.printStackTrace();
return Collections.EMPTY_LIST;
} System.out.println("4");
return list;
}
but when I called it from client by the following way:
...............
List lt = new ArrayList();
lt = tb_user.getResultset("select * from tb_user"); ---error here
//tb_user ---EJB Object
..............

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