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 = "[e-mail]"; String mailFrom = "[e-mail]"; 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

Answer 1

JDK 9默认禁用对许多javax。* API的访问，现在不推荐使用javax激活。

但是，您可以在运行时添加模块来解决它

 "--add-modules java.activation".