！

您的消息内容返回String，您正在尝试键入转换为Multipart。

Your message content returning String and you are trying to type cast to Multipart.

Object content = msg.getContent();  
if (content instanceof String)  
{  
    String body = (String)content;  
    ...  
}  
else if (content instanceof Multipart)  
{  
    Multipart mp = (Multipart)content;  
    ...  
}