java.lang.ClassCastException:无法将java.util.ArrayList强制转换为javax.faces.model.SelectItem

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我正在尝试使下拉菜单动态化，以下是我得到的代码和异常.请帮帮我

I am trying to make my dropdown dynamic and below is the code and exception i am getting. Please help me out

bean:

private String dropDownValue; List<SelectItem> testDropDown = new ArrayList<SelectItem>(); List<SelectItem> testDropDownTwo = new ArrayList<SelectItem>(); public String getDropDownValue() { return dropDownValue; } public void setDropDownValue(String dropDownValue) { this.dropDownValue = dropDownValue; } public List<SelectItem> getTestDropDown() { testDropDown.add(new SelectItem("One")); testDropDown.add(new SelectItem("Two")); testDropDown.add(new SelectItem("Three")); testDropDown.add(new SelectItem("Four")); return testDropDown; }

XHtml代码:

<h:selectOneMenu value="#{loginBean.dropDownValue}"> <f:selectItem value="#{loginBean.testDropDown}" /> </h:selectOneMenu>

例外:

例外

javax.servlet.ServletException: java.util.ArrayList cannot be cast to javax.faces.model.SelectItem javax.faces.webapp.FacesServlet.service(FacesServlet.java:321) root cause java.lang.ClassCastException: java.util.ArrayList cannot be cast to javax.faces.model.SelectItem com.sun.faces.renderkit.SelectItemsIterator.initializeItems(SelectItemsIterator.java:185) com.sun.faces.renderkit.SelectItemsIterator.hasNext(SelectItemsIterator.java:131) com.sun.faces.renderkit.html_basic.MenuRenderer.renderOptions(MenuRenderer.java:758) com.sun.faces.renderkit.html_basic.MenuRenderer.renderSelect(MenuRenderer.java:840) com.sun.faces.renderkit.html_basic.MenuRenderer.encodeEnd(MenuRenderer.java:294) javax.facesponent.UIComponentBase.encodeEnd(UIComponentBase.java:879) javax.facesponent.UIComponent.encodeAll(UIComponent.java:1650)

某些类广播异常正在发生.但是我正在将SelectItem的ArrayList发送到列表中

Some classcast exception is happening. but i am sending the ArrayList of SelectItem to the list

如果我将selectItem标记中的Value属性更改为itemValue，则不会引发异常，但不会获得任何值，我会获得对象名称，如在单个列表中的下拉列表中一样

if i change the Value attribute in selectItem tag to itemValue it is not trowing a exception but i am not getting any value i am getting the object names as in the drop down in a single list

推荐答案

您必须使用f:selectItems:

<h:selectOneMenu value="#{loginBean.dropDownValue}"> <f:selectItems value="#{loginBean.testDropDown}"/> </h:selectOneMenu>

f:selectItem用于在菜单中添加单个SelectItem，要添加SelectItems的整个List，则必须使用此标记.

f:selectItem is used to add a single SelectItem to the menu, to add a whole List of SelectItems you have to use this tag.