如何更正无效协议：使用javax.mail发送邮件为空

我正试图以这种方式发送邮件：

Properties props = new Properties();
props.setProperty("mail.transport.protocol", "smtp");
props.setProperty("mail.host", "out.alice.it");
props.setProperty("mail.user", "mymail@domain.it");
props.setProperty("mail.password", "*****");
Session mailSession = Session.getDefaultInstance(props, null);
Transport transport = mailSession.getTransport();
MimeMessage message = new MimeMessage(mailSession);
message.setFrom(new InternetAddress("Host", "Name"));

在行传输传输…我检索此错误：

javax.mail.NoSuchProviderException: Invalid protocol: null
    at javax.mail.Session.getProvider(Session.java:440)
    at javax.mail.Session.getTransport(Session.java:659)
    at javax.mail.Session.getTransport(Session.java:640)
    at javax.mail.Session.getTransport(Session.java:626)
    at Mail.sendMail(Mail.java:151)

我怎么解决？有人能帮我吗？谢谢！！

标签：java,javax-mail,nosuchproviderexception
来源： https://codeday.me/bug/20190902/1787714.html