我正在尝试使用AutoPopulatingList创建一个动态填充的列表。我也有一个表单对象，如下面的代码所示：
public class CDNoteForm{
private AbstractCDNote cdnote;
private List<? extends AbstractInvoiceItem> invoiceItemList ;
public CDNoteForm() {
super();
}
public CDNoteForm(String type){
super();
if(type.equals("cdnote")){
this.invoiceItemList = new AutoPopulatingList<CDNoteItem>(CDNoteItem.class);
}
else if(type.equals("vendorcdnote")) {
this.invoiceItemList = new AutoPopulatingList<VendorCDNoteItem>(VendorCDNoteItem.class);
}
}
public AbstractCDNote getCdnote() {
return cdnote;
}
public void setCdnote(AbstractCDNote cdnote) {
this.cdnote = cdnote;
}
public List<? extends AbstractInvoiceItem> getInvoiceItemList() {
return invoiceItemList;
}
public void setInvoiceItemList(List<? extends AbstractInvoiceItem> invoiceItemList) {
this.invoiceItemList = invoiceItemList;
}
}
表单对象在我的控制器的方法中声明，如下所示。
@RequestMapping(value ="/cdnote/create" , method = RequestMethod.GET)
public String getCreateCDNotePage(Model model){
CDNoteForm cdnoteForm = new CDNoteForm("cdnote");
model.addAttribute("CDNoteForm" , cdnoteForm);
return "AddCDNote";
}
像这样在jsp中引用“ invoiceItemList”
<form:input type="text" id="Quantity0" path="invoiceItemList[0].quantity" class="form-control"></form:input>
“ CDNoteItem”和“ VendorCDNoteItem”这两个类扩展了抽象类“ AbstractInvoiceItem”。现在，编译时没有任何错误，但是当我尝试运行它并访问该页面时，在控制台上出现以下错误。
SEVERE: Servlet.service() for servlet [SpringGST] in context with path [/SpringGST] threw exception [org.springframework.beans.InvalidPropertyException: Invalid property 'invoiceItemList[0]' of bean class [com.gst.FormObjects.CDNoteForm]: Illegal attempt to get property 'invoiceItemList' threw exception; nested exception is org.springframework.beans.NullValueInNestedPathException: Invalid property 'invoiceItemList' of bean class [com.gst.FormObjects.CDNoteForm]: Could not instantiate property type [com.gst.models.AbstractInvoiceItem] to auto-grow nested property path: org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.gst.models.AbstractInvoiceItem]: Is it an abstract class?; nested exception is java.lang.InstantiationException] with root cause
org.springframework.beans.NullValueInNestedPathException: Invalid property 'invoiceItemList' of bean class [com.gst.FormObjects.CDNoteForm]: Could not instantiate property type [com.gst.models.AbstractInvoiceItem] to auto-grow nested property path: org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.gst.models.AbstractInvoiceItem]: Is it an abstract class?; nested exception is java.lang.InstantiationException
我不明白为什么在初始化“ invoiceItemlist”并引用其子类的自动填充列表时尝试实例化抽象类“ AbstractInvoiceItem”
最佳答案
您可以使用invoiceItemList.get（0）代替invoiceItemList [0]并尝试