JSF - How to use database row values to generate additional columns in datatable

So what you basically want is to do a join between the result of a query to a database and the webservice.

Of course you don't need to load the entire DB in some bean to do this "join", just load the data you would like to display on screen in a backing bean, load the addresses for each row, and bind the result to the datatable.

Something like this:

@ManagedBean
@ViewScoped
public class MyBean {

    @EJB
    private someDataService;

    @EJB
    private someWebService;

    List<Person> persons;
    Map<Long, String> addresses;

    @PostConstruct
    public void retrieveData() {
        persons = someDataService.getByID(someID);
        for (Person person : persons) {
            addresses.put(person.getID(), someWebService.getByID(person.getID));
        }
    }

    // getters here
}

And the Facelet:

<h:dataTable value="#{myBean.persons}" var="person">
    <h:column>
        #{person.name}
    </h:column>
    <h:column>
        #{person.lastName}
    </h:column>
    <h:column>
        #{myBean.addresses[person.ID]}      
    </h:column>             
</h:dataTable>

There are some choices to be made. You could also do the joining inside a single service and have it return some type that includes the address. You could also make a wrapper or a decorator.

It would also be more efficient if the web service could handle a list of IDs instead of requiring a separate call for each address fetched. You might also wanna do some local caching, etc, but those details are up to you ;)