带附件的Java邮件：javax.mail.Multipart上的ClassCastException [英] Java mail with attachment: ClassCastException on javax.mail.Multipart

问题描述

我使用以下代码从邮件中下载附件，但它在Multipart声明中给出 ClassCastException ：

I use the following code to download the attachment from the mail but it gives the ClassCastException on the Multipart declaration:

线程main中的异常java.lang.ClassCastException：com.sun.mail.imap.IMAPInputStream无法在ReadAttachment.main（ReadAttachment）中强制转换为javax.mail.Multipart
.java：52）

Exception in thread "main" java.lang.ClassCastException: com.sun.mail.imap.IMAPInputStream cannot be cast to javax.mail.Multipart at ReadAttachment.main(ReadAttachment.java:52)

如何处理IMAPInputStream？

How do I handle IMAPInputStream?

Message messages[] = inbox.getMessages();

for (int j = 0; j < messages.length; j++) {

   String mailType = messages[j].getContentType();

   System.out.println("-- Message " + (j + 1) + " --");

   System.out.println("SentDate : " + messages[j].getSentDate());
   System.out.println("From : " + messages[j].getFrom()[0]);
   System.out.println("Subject : " + messages[j].getSubject());             
   System.out.println("Type :" + messages[j].getContentType()); 
   System.out.println("Attachment :" + messages[j].getFileName());  

   Multipart mp = (Multipart) messages[j].getContent();
   ..

   System.out.println();
}

推荐答案

我遇到了同样的问题JavaMail 1.5.1和OSGi。使用msg.getContent（）时，从OSGi包调用时总是返回一个InputStream，而当从一个简单的Java测试程序调用它时它是完美的。

I had the same problem with the JavaMail 1.5.1 and OSGi. Using msg.getContent() always returned an InputStream when called from an OSGi bundle while it works perfectly when called from a simple Java test program.

设置默认的CommandMap didn'为我工作，但我在这里找到了解决方案：

Setting the default CommandMap didn't work for me, but I found a solution here:

https://www.java.net/node/705585

ClassLoader tcl = Thread.currentThread().getContextClassLoader();
try {
    Thread.currentThread().setContextClassLoader(javax.mail.Session.class.getClassLoader());
    // now call JavaMail API
    // ...
} finally {
    Thread.currentThread().setContextClassLoader(tcl);
}

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