java - Eclipse:java.lang.NoClassDefFoundError:javax/activation/DataHandler

我正在尝试用Java发送电子邮件。
这是代码:

String mailSmtpHost = "smtp.example.com";
String mailTo = "[email protected]";
        String mailFrom = "[email protected]";
        String mailSubject = "Email subject";
        String mailText = "Some text";
        Properties properties = new Properties();
        properties.put("mail.smtp.host", mailSmtpHost);
        Session emailSession = Session.getDefaultInstance(properties);
try {
            Message emailMessage = new MimeMessage(emailSession);
            emailMessage.addRecipient(Message.RecipientType.TO, new InternetAddress(mailTo));
            emailMessage.setFrom(new InternetAddress(mailFrom));
            emailMessage.setSubject(mailSubject);
            emailMessage.setText(mailText);
            emailSession.setDebug(true);
            Transport.send(emailMessage);
        }catch(Exception e) {
            System.out.println("Errore email: "+e.toString());
        }

当我编译项目时，在线:

Message emailMessage = new MimeMessage(emailSession);

...出现以下错误:

Exception in thread "main" java.lang.NoClassDefFoundError: javax/activation/DataHandler

注意:我使用的是java -version: 9.0.4

最佳答案

JDK 9默认禁用对许多javax。* API的访问，现已弃用javax激活。

但是，您可以通过在运行时添加模块来解决它

"--add-modules java.activation".