使用MultiPartEmail发送带附件的电子邮件

Question

我正在尝试使用此方法发送附带hello.json文件的电子邮件。但是当我构建并运行代码时，电子邮件会被发送，但是附件从未通过电子邮件发送。我缺少的MultPartEmail API有什么特别之处吗？我的代码基于其他示例。

public void sendNotification(String from, String pass, String host, int port, String[] to,
  String subject, String body) throws EmailException {
    log.trace("Beginning sendNotification function");

    EmailAttachment attachment = new EmailAttachment();
    attachment.setPath("C:/temp/hello.json");
    attachment.setDisposition(EmailAttachment.ATTACHMENT);
    attachment.setName("user");
    attachment.setDescription("external json file");

    File f = new File("C:/temp/hello.json");

    MultiPartEmail gmail = new MultiPartEmail();
    gmail.setSmtpPort(port);
    gmail.setHostName(host);
    gmail.setAuthentication(from, pass);
    gmail.setSSLOnConnect(true);
    gmail.setFrom(from);
    gmail.setSubject(subject);
    gmail.setContent(body, "text/html; charset=utf-8");
    gmail.addTo(to);
    if (f.exists() && !f.isDirectory()) {
    gmail.attach(attachment);
    } else {
    log.error(String.format("%s does not exist.", attachment));
    }
    gmail.send();
}