使用 Java 邮件下载附件

java attachment jakarta-mail

2022-08-31 10:27:27

现在我已经下载了所有消息，并将它们存储到

Message[] temp;

如何获取每封邮件的附件列表

List<File> attachments;

注意：没有第三方库，拜托，只有JavaMail。

答案 1

没有异常处理，但这里是：

List<File> attachments = new ArrayList<File>();
for (Message message : temp) {
    Multipart multipart = (Multipart) message.getContent();

    for (int i = 0; i < multipart.getCount(); i++) {
        BodyPart bodyPart = multipart.getBodyPart(i);
        if(!Part.ATTACHMENT.equalsIgnoreCase(bodyPart.getDisposition()) &&
               StringUtils.isBlank(bodyPart.getFileName())) {
            continue; // dealing with attachments only
        } 
        InputStream is = bodyPart.getInputStream();
        // -- EDIT -- SECURITY ISSUE --
        // do not do this in production code -- a malicious email can easily contain this filename: "../etc/passwd", or any other path: They can overwrite _ANY_ file on the system that this code has write access to!
//      File f = new File("/tmp/" + bodyPart.getFileName());
        FileOutputStream fos = new FileOutputStream(f);
        byte[] buf = new byte[4096];
        int bytesRead;
        while((bytesRead = is.read(buf))!=-1) {
            fos.write(buf, 0, bytesRead);
        }
        fos.close();
        attachments.add(f);
    }
}

答案 2

问题很古老，但也许它会帮助某人。我想扩展David Rabinowitz的答案。

if(!Part.ATTACHMENT.equalsIgnoreCase(bodyPart.getDisposition()))

不应像预期的那样返回所有 atachment，因为您可以在没有定义处置的混合部分的情况下拥有邮件。

   ----boundary_328630_1e15ac03-e817-4763-af99-d4b23cfdb600
Content-Type: application/octet-stream;
    name="00000000009661222736_236225959_20130731-7.txt"
Content-Transfer-Encoding: base64

因此，在这种情况下，您还可以检查文件名。喜欢这个：

if (!Part.ATTACHMENT.equalsIgnoreCase(part.getDisposition()) && StringUtils.isBlank(part.getFileName())) {...}

编辑

有完整的工作代码使用上面描述的条件。由于每个部件可以封装另一个部件并且附件应嵌套在其中，因此递归用于遍历所有部件

public List<InputStream> getAttachments(Message message) throws Exception {
    Object content = message.getContent();
    if (content instanceof String)
        return null;        

    if (content instanceof Multipart) {
        Multipart multipart = (Multipart) content;
        List<InputStream> result = new ArrayList<InputStream>();

        for (int i = 0; i < multipart.getCount(); i++) {
            result.addAll(getAttachments(multipart.getBodyPart(i)));
        }
        return result;

    }
    return null;
}

private List<InputStream> getAttachments(BodyPart part) throws Exception {
    List<InputStream> result = new ArrayList<InputStream>();
    Object content = part.getContent();
    if (content instanceof InputStream || content instanceof String) {
        if (Part.ATTACHMENT.equalsIgnoreCase(part.getDisposition()) || StringUtils.isNotBlank(part.getFileName())) {
            result.add(part.getInputStream());
            return result;
        } else {
            return new ArrayList<InputStream>();
        }
    }

    if (content instanceof Multipart) {
            Multipart multipart = (Multipart) content;
            for (int i = 0; i < multipart.getCount(); i++) {
                BodyPart bodyPart = multipart.getBodyPart(i);
                result.addAll(getAttachments(bodyPart));
            }
    }
    return result;
}