org.springframework.mail.MailSendException：失败的消息：java.lang.NullPointerException

Question

我在尝试使用 Spring Boot 电子邮件功能时遇到以下异常：

Caused by: org.springframework.mail.MailSendException: Failed messages: java.lang.NullPointerException

这是我的邮件配置类：

@Configuration
public class MailConfiguration {

    private final MailProperties mailProperties;

    @Autowired
    public MailConfiguration (MailProperties mailProperties) {
        this.mailProperties = mailProperties;
    }

    @Bean
    public JavaMailSender javaMailSender() {
        JavaMailSenderImpl mailSender = new JavaMailSenderImpl();
        Properties properties = new Properties();
        properties.put("mail.smtp.auth", mailProperties.getSmtp().isAuth());
        properties.put("mail.smtp.starttls.enable", mailProperties.getSmtp().isStarttlsEnable());
        mailSender.setJavaMailProperties(properties);
        mailSender.setHost(mailProperties.getHost());
        mailSender.setPort(mailProperties.getPort());
        mailSender.setProtocol(mailProperties.getProtocol());
        mailSender.setUsername(mailProperties.getUsername());
        mailSender.setPassword(mailProperties.getPassword());
        return mailSender;
    }
}

这是邮件属性类：

@Configuration
@ConfigurationProperties(prefix = "mail", locations = "classpath:mail.properties")
public class MailProperties {

    public static class Smtp {
        private boolean auth;
        private boolean starttlsEnable;

        public boolean isAuth () {
            return auth;
        }

        public void setAuth (boolean auth) {
            this.auth = auth;
        }

        public boolean isStarttlsEnable () {
            return starttlsEnable;
        }

        public void setStarttlsEnable (boolean starttlsEnable) {
            this.starttlsEnable = starttlsEnable;
        }
    }

    @NotBlank
    private String host;
    private int port;
    private String from;
    private String username;
    private String password;
    private String protocol;

    @NotNull
    private Smtp smtp;

    public String getHost () {
        return host;
    }

    public void setHost (String host) {
        this.host = host;
    }

    public int getPort () {
        return port;
    }

    public void setPort (int port) {
        this.port = port;
    }

    public String getFrom () {
        return from;
    }

    public void setFrom (String from) {
        this.from = from;
    }

    public String getUsername () {
        return username;
    }

    public void setUsername (String username) {
        this.username = username;
    }

    public String getPassword () {
        return password;
    }

    public void setPassword (String password) {
        this.password = password;
    }

    public Smtp getSmtp () {
        return smtp;
    }

    public void setSmtp (Smtp smtp) {
        this.smtp = smtp;
    }

    public String getProtocol () {
        return protocol;
    }

    public void setProtocol (String protocol) {
        this.protocol = protocol;
    }
}

这是邮件服务类：

public class MailServiceImpl implements MailService {

    private final JavaMailSender javaMailSender;

    private static final Logger log = LoggerFactory.getLogger(MailServiceImpl.class);

    @Autowired
    public MailServiceImpl (JavaMailSender javaMailSender) {
        this.javaMailSender = javaMailSender;
    }


    @Override
    public void send (String receiver, String sender, String message, String filenameAndLocation) {
        SimpleMailMessage msg = new SimpleMailMessage();
        msg.setText(receiver);
        msg.setFrom(sender);
        msg.setText(message);
        msg.setSubject("testing subject");
        javaMailSender.send(msg);
    }
}

我只是尝试调用这样的方法：mailService.send("someone@com.com", "someone@com.com", "test", "test");

Answer 1

我的邮件服务类不正确，这是正确的：

@Service
public class MailServiceImpl implements MailService {

    private final JavaMailSender javaMailSender;

    private static final Logger log = LoggerFactory.getLogger(MailServiceImpl.class);

    @Autowired
    public MailServiceImpl (JavaMailSender javaMailSender) {
        this.javaMailSender = javaMailSender;
    }


    @Override
    public void send (String receiver, String sender, String message, String filenameAndLocation) {
        MimeMessagePreparator preparator = new MimeMessagePreparator() {
            @Override
            public void prepare (MimeMessage mimeMessage) throws Exception {
                MimeMessageHelper messageHelper = new MimeMessageHelper(mimeMessage);
                messageHelper.setTo(receiver);
                messageHelper.setFrom(sender);
                messageHelper.setSubject("test subject");
                messageHelper.setText(message);
            }
        };
        this.javaMailSender.send(preparator);
    }
}