NullPointerException - 用Java发送电子邮件（使用Spring库）

Question

我无法在我的网络应用程序中发送电子邮件，这有点不对劲 MimeMessage message = javaMailSender.createMimeMessage();行，这是一段代码：

MailSender：

private JavaMailSender javaMailSender;  

public void send(String from, String to, String subject, String body)  throws MessagingException {

    MimeMessage message = javaMailSender.createMimeMessage();
    MimeMessageHelper helper;

    helper = new MimeMessageHelper(message, true); 

    helper.setFrom(from);
    helper.setSubject(subject);
    helper.setTo(to);
    helper.setText(body, true); 


    javaMailSender.send(message);   
}

错误：

 SEVERE: Servlet.service() for servlet [spring-dispatcher] in context with path [/OnlineShop] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause
java.lang.NullPointerException
at com.damian.model.MailSender.send(MailSender.java:19)