转换器类引发异常java.lang.IollegalArgumentException

Question

我的JSF页面中有p:selectOneMenu，当我运行JSF页面时，我从Converter类中得到以下异常。

java.lang.IllegalArgumentException: object 5634 is of type java.lang.String; 
expected type: test.entity.Employee

如何解决此问题？

我在实体类中有以下内容

@Entity
public class Employee implements Serializable {
private String employeeNumber;
private String employeeName;
/* getters and setters */

EmployeeConverter类

@Component("employeeConverter")
@FacesConverter(forClass = Employee.class)
@Inject
EmployeeService employeeService;
@Override
public Object getAsObject(FacesContext facesContext, UIComponent component, String value) {
    if (value == null || value.length() == 0) {
        return null;
    }
    EmployeeService employeeService= (EmployeeService ) facesContext.getApplication().getELResolver().
            getValue(facesContext.getELContext(), null, "employeeService");
    return employeeService.getEmployees();
}
@Override   
public String getAsString(FacesContext facesContext, UIComponent component, Object object) {
            if (object == null) {
                return null;
            }
            if (object instanceof Employee) {
                Employee emp = (Employee) object;
                String val = emp.getEmployeeNumber();
                return val;
            } else {
throw new IllegalArgumentException("object " + 
object + " is of type " + object.getClass().getName() + "; expected type: " +
Employee.class.getName());
            }
}

以及在jsf页面中

 <p:selectOneMenu value="#{mb.employee}" converter="#{employeeConverter}">
 <f:selectItems value="#{cmb.employeeList}" var="emp"
 itemLabel="#{emp.employeeName}" itemValue="#{emp.employeeNumber}"/>
 <p:ajax  listener="#{mb.handleChange}"  process="@this"/>
 </p:selectOneMenu>

更新1

改进的转换器方法getAsObject

private List<Employee> employee;
@Override
    public Object getAsObject(FacesContext facesContext, UIComponent component,
            String value) {
        System.out.println("reached in converter");
        try {
            if (value == null || value.length() == 0) {
                return null;
            } else {
                employee = getEmployeeService().getEmployees();
                for (Employee emp : employee) {
                    if (emp.getEmployeeNUmber() == value) {
                        return emp;
                    }
                }
            }
        } catch (Exception e) {
            System.out.println("exception from getAsObject  " + e.getMessage());            
        }
        return null;
    }

更新2

ManagedBean
@PostConstruct
    public void loadEmployees(){
        try {           
            List<Employee> emp = getEmployeeService().getEmployees();           
            employeeList = emp; 
        }
        catch(Exception e){
            e.printStackTrace();
            System.out.println("exception from loadEmployees "+e.getMessage());
        }
    }

Answer 1

不要将字符串分配给项值，您需要分配转换后的对象（Employee）本身。

更改为itemValue="#{emp}"

请参阅BalusC对此问题的回答。

Answer 2

在getAsObject方法中，您对所达到的值没有做任何操作。在这里，您将收到您的#{emp.employeeNumber}，因此您必须将其转换为Employee（可能您必须实现一个方法，该方法使用服务定位器通过id加载Employee），并返回对象本身。

您还使用EL（#{employeeConverter}）引用转换器，必须以直接的方式进行。最后，元素列表必须由SelectItem组成，才能使f:selectItems标签工作。