Then in what case , where and how the @Transient Annotation wouild be useful to anyone ??
By default all the properties of a POJO are marked for persisting. So if you want to skip any properties from being persisted, you can add the @Transient.
For an example, if you need to manage a temporary-state on the bean, you can use the @Transient annotation, so that it will not be mapped to the database.
A practical example is user enters a password in the form and it has a field in the backing bean so that bean and you pass that backing bean across the wires through some webservices or EJB then if you mark the password field as transient it won't be passed across the wires.