使用： 蒙戈-Java的应用程序，3.2.2.jar 和 吗啡-1.1.1.jar
代码：
for (UserList userList: userLists){
DBObject userListDbObj = SingletonLaunchDB.getMorphia().toDBObject(userList);
SingletonLaunchDB.getMongo().save(userListDbObj);
}
错误追踪：
Grave: java.lang.RuntimeException: Generic TypeVariable not supported!
at org.mongodb.morphia.mapping.MappedField.toClass(MappedField.java:616)
at org.mongodb.morphia.mapping.EphemeralMappedField.getSubClass(EphemeralMappedField.java:84)
at org.mongodb.morphia.mapping.EphemeralMappedField.<init>(EphemeralMappedField.java:39)
at org.mongodb.morphia.mapping.MappedField.discoverType(MappedField.java:498)
at org.mongodb.morphia.mapping.MappedField.discover(MappedField.java:465)
at org.mongodb.morphia.mapping.MappedField.<init>(MappedField.java:93)
at org.mongodb.morphia.mapping.MappedClass.discover(MappedClass.java:540)
at org.mongodb.morphia.mapping.MappedClass.<init>(MappedClass.java:124)
at org.mongodb.morphia.mapping.Mapper.getMappedClass(Mapper.java:431)
at org.mongodb.morphia.DatastoreImpl.getWriteConcern(DatastoreImpl.java:1632)
at org.mongodb.morphia.DatastoreImpl.save(DatastoreImpl.java:686)
UserList是一个未注明@Entity并且没有@Id字段的类，原因是什么？