Primefaces自动完成ClassCastException

Question

I am using Spring 3, Hibernate 4 and JSF 2.0 and am trying to do primefaces autocomplete.

I have the following in DAO class to get values from Oracle function

@Override
    public List<EmployeeDetail> getEmployeeDetails(String employeeNumber) {

        List query = (List)entityManager.createNamedQuery("getEmp")
                .setParameter("empNumber", employeeNumber)
                .getSingleResult();

        return query;

    }

Converter class

public EmployeeNameConverter(

            List<EmployeeDetail> employeeDB, EmployeeDetailService instance,
                    String employeeNumber) {
                if (employeeDetailService == null) {
                    employeeDetailService = instance;
                }
                if (param == null) {
                    param = employeeNumber;
                }
                this.employeeDB = employeeDB;
            }

@Override
    public Object getAsObject(FacesContext arg0, UIComponent arg1,
            String submittedValue) {
        if (submittedValue.trim().equals("")) {
            return null;
        } else {
            try {
                // int number = Integer.parseInt(submittedValue);
                employeeDB = getEmployeeDetailService().getEmployeeDetails(param);
                for (EmployeeDetail emp : employeeDB) {
                    if (emp.getEmployeeNumber() == submittedValue) {
                        return emp;
                    }
                }

            } catch (NumberFormatException exception) {
                throw new ConverterException(new FacesMessage(
                        FacesMessage.SEVERITY_ERROR, "Conversion Error",
                        "Not a valid employee"));
            }
        }

In my Managedbean

I have complete method where I am passing employeeDetailService to my converter class.

public List<EmployeeDetail> complete(String query) {
        List<EmployeeDetail> suggestions;
        suggestions = new ArrayList<EmployeeDetail>();
        try {
            employee =  (List<EmployeeDetail>) new EmployeeNameConverter(
                    employeeList, employeeDetailService, query);

            for (EmployeeDetail p : employee) {
                if (p.getEmployeeNumber().startsWith(query))
                    suggestions.add(p);
            }
        } catch (Exception e) {
            System.out.println("exc " + e.getMessage());
            e.printStackTrace();
        }

        return suggestions;
    }

JSF Code

<p:autoComplete value="#{empMB.selectedEmployee}"
                            id="basicPojo" minQueryLength="6" 
                            completeMethod="#{empMB.complete}" var="p"
                            itemLabel="#{p.employeeNumber}" 
                            itemValue="#{p}" converter="#{p.employee}"
                            forceSelection="true" />

When I type in characters I am getting exception

EmployeeNameConverter cannot be cast to java.util.List
java.lang.ClassCastException: net.test.util.EmployeeNameConverter cannot be cast to java.util.List

How can I resolve this? Is this the correct approach or could someone kindly suggest better approach in achieving the same?

Update 1

@Override
    public List<EmployeeDetail> getEmployeeDetails(String employeeNumber) {

        List query = (List)entityManager.createNamedQuery("getEmp")
                .setParameter("empNumber", employeeNumber)
                .getSingleResult();

        return query;

    }

Exception

net.test.entity.EmployeeDetail cannot be cast to java.util.List
java.lang.ClassCastException: net.test.entity.EmployeeDetail cannot be cast to java.util.List
    at net.test.dao.EmployeeDetailDAOImpl.getEmployeeDetails(EmployeeDetailDAOImpl.java:36)

and exception line is

List query = (List)entityManager.createNamedQuery("getEmp")
                    .setParameter("empNumber", employeeNumber)
                    .getSingleResult();

Answer 1

There are two main issues apparent here

1. You're attempting to instantiate and manage a JSF converter instance by hand. Don't do this. The converter is a construct designed for use by the JSF context only. It's not the job of you the developer to call new or supply constructor arguments to the converter class. Implement a simple converter per this example and configure on the <p:autoComplete/>

   From your comments, the reason you've taken to managing the converter by hand is to be able to access your DAO layer. As a workaround, you can add @ManagedBean to your converter and JSF will treat is as a managed bean and a converter. Being a managed bean, you'll now be able to inject your DAO resource into it. This is not best practice, but only a workaround. This limitation on converters will be removed in JSF2.2 though :).

2. While manipulating the converter, you're attempting to treat it like a regular POJO and trying to cast it into several incompatible types as a result

    employee = (List<EmployeeDetail>) new EmployeeNameConverter( employeeList, employeeDetailService, query); //EmployeeNameConverter !instanceof EmployeeDetail