Question

我正在尝试将转换器用于输入表单，其中我使用了一些＆＃34; selectOneMenu＆＃34;组件。

当我尝试在转换器中获取我的控制器对象＆＃34; getAsObject＆＃34;方法使用：

facesContext.getApplication().getELResolver().
                getValue(facesContext.getELContext(), null, "usersController");

我总是空着。这是我的转换器类，它嵌套在UserController类中。

@FacesConverter(forClass = User.class, value="userConverter")
public static class UsersControllerConverter implements Converter {

    @Override
    public Object getAsObject(FacesContext facesContext, UIComponent component, String value) {
        if (value == null || value.length() == 0) {
            return null;
        }
        UserController controller = (UserController) facesContext.getApplication().getELResolver().
                getValue(facesContext.getELContext(), null, "usersController");
        System.out.println(value);
        System.out.println(getKey(value));
        System.out.println(controller);
        return controller.getUsers(getKey(value));
    }

    java.lang.String getKey(String value) {
        java.lang.String key;
        key = value;
        return key;
    }

    String getStringKey(java.lang.String value) {
        StringBuilder sb = new StringBuilder();
        sb.append(value);
        return sb.toString();
    }

    @Override
    public String getAsString(FacesContext facesContext, UIComponent component, Object object) {
        if (object == null) {
            return null;
        }
        if (object instanceof User) {
            User o = (User) object;
            return getStringKey(o.getUsername());
        } else {
            throw new IllegalArgumentException("object " + object + " is of type " + object.getClass().getName() + "; expected type: " + User.class.getName());
        }
    }

}

UserController类声明：

@Named("userController")
@ManagedBean
@SessionScoped
public class UserController implements Serializable{

PS：我是新手，我刚开始学习Java EE / Faces。

Answer 1

此，

UserController controller = (UserController) facesContext.getApplication().getELResolver().
    getValue(facesContext.getELContext(), null, "usersController");

确实不是正确的方法。以下是正确的方法：

UserController controller = facesContext.getApplication().evaluateExpressionGet(
    facesContext, "#{usersController}", UsersController.class);

JSF FacesConverter ELResolver.getValue返回null

1 个答案: