mysql - 从 using jsf2 中的数据库填充数据

Question

I'm using selectOneMenu from primefaces to populate data from mysql database, but i constantly get empty fields and i dont receive any errors. Can somebody explain what am i doing wrong?

This is my code:

xhtml 文件:

    <p:selectOneMenu id="point" value="#{pointController.selectedPoint}"
                     var="items_var"> 

         <f:selectItems value="#{pointController.points}" var="points_var" 
                        itemLabel="#{points_var.name}" itemValue="#{points_var.name}"/>

    </p:selectOneMenu>

托管 bean:

    @ManagedBean(name = "pointController")
    @SessionScoped

    public class PointController implements Serializable {

    @EJB
        private ethoam.entity.PointFacade ejbFacade;
        private List<point> points;
        private point selectedPoint;
        private point[] selectedPoints;
        private List<Point> selectedPointsList;
        private SelectItem[] PointNamesOptions;

        public PointController() {
                  this.initList();
        }

        @PostConstruct
        private void initList() {

        points = new ArrayList<point>(pointControllerConverter.getPoints().values());


    }

        // getters setters
     }

和转换器类:

    public static class PointControllerConverter implements Converter {

    @PersistenceContext(unitName = "PointPU")
    private static EntityManager ejbfacade;

    public static Map<String, point> points = new HashMap<String, point>();

    public Map<String,point> getPoints() {

    points = (Map<String, point>) ejbfacade.getEntityManager().createNamedQuery("SELECT d FROM point d WHERE d.name = :name");
    return points;
    }

    @Override
    public Object getAsObject(FacesContext facesContext, UIComponent component, String value) {
        if (value == null || value.length() == 0) {
            return null;
        }
        PointController controller = (PointController) facesContext.getApplication().getELResolver().
                getValue(facesContext.getELContext(), null, "pointController");
        return controller.ejbFacade.find(getKey(value));
    }

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

    String getStringKey(java.lang.Integer 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 point) {
            point o = (point) object;
            return getStringKey(o.getIdPoint());
        } else {
            throw new IllegalArgumentException("object " + object + " is of type " + object.getClass().getName() + "; expected type: " + Point.class.getName());
        }
    }

}

Answer 1

您将一个字符串定义为值 ( itemValue="#{points_var.name}" )，并且您的组件需要一个 point 实例。

这是您需要考虑的更改之一:

<p:selectOneMenu id="point" value="#{pointController.selectedPoint}" var="items_var"> 
    <f:selectItems value="#{pointController.points}" var="points_var" itemLabel="#{points_var.name}" itemValue="#{points_var}"/>
</p:selectOneMenu>

我还注意到您没有填充 private List<Point> points;使用PointFacade。相反，您使用 PointControllerConverter 内的空静态 Map 中的值实例化 ArrayList。

您的问题表明您正在尝试使用数据库 (MySQL) 中的值填充 selectOnMenu。在这种情况下，您需要重新考虑您的策略并开始使用一些 EJB(如 PointFacade)从数据库中获取数据。