Java Gmail附件处理，Base64DecoderStream到InputStream

我需要从GMail获取附件并上传到AmazonS3

我正在使用imap连接到GMail并能够访问附件， 使用javax.mail.internet.MimeBodyPart，它提供Base64DecoderStream中的getInputStream（），而不是FileInputStream或ByteArray输入流。 因为我的文件是二进制文件（比如.zip）

我需要InputStream将其上传到S3

那么如何将Base64DecoderStream转换为InputStream？

public void processMails() {

    Properties props = new Properties();
    props.setProperty("mail.store.protocol", "imaps");
    Session session = null;
    Store store = null;
    session = Session.getInstance(props, null);
    Folder inboxFolder;
    try {
        store = session.getStore();

        store.connect("imap.gmail.com", "test@gmail.com", "password");
        inboxFolder = store.getFolder("INBOX");
        inboxFolder.open(Folder.READ_WRITE);
        Message messages[] = inboxFolder.search(new FlagTerm(new Flags(Flags.Flag.SEEN), false));   

        for (Message msg : messages) {

            try {
                Multipart multiPart = (Multipart)msg.getContent();
                for (int i = 0; i < multiPart.getCount(); i++) {
                    MimeBodyPart part = (MimeBodyPart) multiPart.getBodyPart(i);
                    if (Part.ATTACHMENT.equalsIgnoreCase(part.getDisposition())) {

 InputStream stream = null;// need to convert part.getInputStream() to InputStream

                        processAttachment(stream);
                    }
                }
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
}

---

如果您需要整个味精流。

ByteArrayOutputStream bos = new ByteArrayOutputStream();
msg.writeTo(bos);
bos.close();
InputStream in = new ByteArrayInputStream(bos.toByteArray());

如果您只需要内容，请尝试此功能

InputStream base64InputStream = (InputStream) part.getInputStream();
int i = 0;
byte[] byteArray = new byte[base64InputStream.available()];
while ((i = (int) ((InputStream) base64InputStream).available()) > 0) {
    int result = (int) (((InputStream) base64InputStream).read(byteArray));
    if (result == -1)
        break;
}
InputStream inputStream = new ByteArrayInputStream(byteArray);

InputStream base64InputStream = (InputStream) part.getInputStream();
int i = 0;
byte[] byteArray = new byte[base64InputStream.available()];
while ((i = (int) ((InputStream) base64InputStream).available()) > 0) {
    int result = (int) (((InputStream) base64InputStream).read(byteArray));
    if (result == -1)
        break;
}
InputStream inputStream = new ByteArrayInputStream(byteArray);