Question

这是我从java教程中获取的代码 - 但是当我尝试接收从计算机发送的正常消息时，我的问题就出现了，而不是通过GMail发送。如果我通过GMail收到电子邮件，它运行正常并返回邮件，但尝试从传统的桌面邮件客户端检索邮件返回

错误：

java.lang.ClassCastException: java.lang.String cannot be cast to javax.mail.Multipart
at gridnotifierproject_pcbuild.HandleMailInput.retrieveOneMail(HandleMailInput.java:37)
at gridnotifierproject_pcbuild.GridNotifierProject_PCBuild.main(GridNotifierProject_PCBuild.java:22)

代码：

Properties props = new Properties();
    props.setProperty("mail.store.protocol", "imaps");
    try {   
        Session session = Session.getInstance(props, null);
        Store store = session.getStore();
        store.connect("imap.gmail.com", "***********@gmail.com", "******");
        System.out.println("Established Connection to Server!");
        Folder inbox = store.getFolder("Inbox");
        inbox.open(Folder.READ_ONLY);
        Message msg = inbox.getMessage(inbox.getMessageCount());
        System.out.println("Found specified Folder, retrieving the latest message...");
        Address[] in = msg.getFrom();
        for (Address address : in) {
            System.out.println("FROM:" + address.toString());
        }
        Multipart mp = (Multipart) msg.getContent();
        BodyPart bp = mp.getBodyPart(0);
        System.out.println("SENT DATE:" + msg.getSentDate());
        System.out.println("SUBJECT:" + msg.getSubject());
        System.out.println("CONTENT:" + bp.getContent());
    } catch (Exception mex) {
        mex.printStackTrace();
    }

Answer 1

首先了解异常!!!

您的邮件内容返回String并且您正尝试将强制转换为Multipart。

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

Answer 2

并非所有消息都是多部分的。您需要了解MIME消息的结构。从this JavaMail FAQ entry开始。然后查看msgshow.java sample program。

java.lang.ClassCastException：java.lang.String无法强制转换为javax.mail.Multipart

2 个答案: