java.lang.ClassCastException：

Question

任何人都可以帮助解决 EWS 中的以下问题，我收到一个错误 java.lang.ClassCastException: microsoft.exchange.webservices.data.property.complex.ItemAttachment cannot be cast to microsoft.exchange.webservices.data.property.complex.FileAttachment    private static void readAttachment(ExchangeService service, Folder folder, int n) {    ItemView view = new ItemView(n);    FindItemsResults<Item> findResults;    try {    findResults = service.findItems(folder.getId(), view);    System.out.println("findResults-->"+findResults.getTotalCount());    for (Item item : findResults) {        EmailMessage email;            email = EmailMessage.bind(service, item.getId(), new PropertySet(BasePropertySet.IdOnly, ItemSchema.Attachments));            System.out.println("email.getAttachments().getCount()-->"+email.getAttachments().getCount());            //email.load();            for (Attachment it : email.getAttachments()) {                System.out.println(it.getName());                FileAttachment iAttachment = (FileAttachment) it;                //iAttachment.load( "C:\\FileLocation\\" + iAttachment .getName());            }    }    } catch (ServiceLocalException e) {        // TODO Auto-generated catch block        e.printStackTrace();    } catch (Exception e) {        // TODO Auto-generated catch block        e.printStackTrace();    }}

Answer 1

这两个FileAttachment和ItemAttachment是直接的子Attachment类。它接缝一些附件是实例，ItemAttachment您正试图将它们转换为FileAttachment. 由于FileAttachmentclass 不是ItemAttachment您的子类，因此您无法对其进行强制转换。

举个例子：

public class Animal {  }

public class Dog extends Animal { }

public class Cat extends Animal { }

Animal a = new Dog();

Cat c = (Cat)a; // this line produces ClassCastException as in your case

在这个例子中你不能