java.io.IOException：使用 Spring Boot 编写 Multipart 时出现异常答案

【问题标题】：java.io.IOException: Exception writing Multipart with SpringBootjava.io.IOException：使用 Spring Boot 编写 Multipart 时出现异常
【发布时间】：2022-01-12 15:54:23
【问题描述】：

我想发送一封带附件的电子邮件：

  public void sendMailWithAttachment(String to, String subject, String body, String fileToAttach) {

        MimeMessagePreparator preparator = mimeMessage -> {

            mimeMessage.setRecipient(Message.RecipientType.TO, new InternetAddress(to));
            mimeMessage.setFrom(new InternetAddress("admin@gmail.com"));
            mimeMessage.setSubject(subject);
            mimeMessage.setText(body);

            FileSystemResource file = new FileSystemResource(new File(fileToAttach));
            System.out.println(file.contentLength());
            MimeMessageHelper helper = new MimeMessageHelper(mimeMessage, true);
            helper.addAttachment("logo.jpg", file);
        };

        try {
            javaMailSender.send(preparator);
        }
        catch (MailException ex) {
            // simply log it and go on...
            System.err.println(ex.getMessage());
        }
    }

但我有这个例外：

Failed messages: javax.mail.MessagingException: IOException while sending message;
  nested exception is:
    java.io.IOException: Exception writing Multipart

【问题讨论】：

标签： java spring-boot file smtp attachment

【解决方案1】：

Spring documentation 中给出的示例与您的代码不匹配：它创建了一个 MimeMessageHelper 对象并使用它来定义正文和附件。

你应该这样做：

public void sendMailWithAttachment(String to, String subject, String body, String fileToAttach) {

        MimeMessagePreparator preparator = mimeMessage -> {

            MimeMessageHelper message = new MimeMessageHelper(mimeMessage, true, "UTF-8");
            message.setRecipient(Message.RecipientType.TO, new InternetAddress(to));
            message.setFrom(new InternetAddress("admin@gmail.com"));
            message.setSubject(subject);
            message.setText(body);

            FileSystemResource file = new FileSystemResource(new File(fileToAttach));
            message.addAttachment("logo.jpg", file);
        };

        try {
            javaMailSender.send(preparator);
        }
        catch (MailException ex) {
            // simply log it and go on...
            System.err.println(ex.getMessage());
        }
    }

【讨论】：

【解决方案2】：

我会以不同的方式创建MimeMessagePreparator 并使用Streams 来读取文件。

public void sendMailWithAttachment(String to, String subject, String body, String fileToAttach) {

        MimeMessagePreparator preparator = mimeMessage -> {

            FileInputStream inputStream = new FileInputStream(new File(fileToAttach));

            MimeMessageHelper message = new MimeMessageHelper(mimeMessage, true, "UTF-8");
            message.setRecipient(Message.RecipientType.TO, new InternetAddress(to));
            message.setFrom(new InternetAddress("admin@gmail.com"));
            message.setSubject(subject);
            message.setText(body);            
            message.addAttachment("logo.jpg", new ByteArrayResource(IOUtils.toByteArray(inputStream)));
  
        };

        try {
            javaMailSender.send(preparator);
        }
        catch (MailException ex) {
            // simply log it and go on...
            System.err.println(ex.getMessage());
        }
    }

【讨论】：

【解决方案3】：

这可能有多种原因。对我来说，这不是设置文本。在你的情况下，如果 body String 为空，你可能会遇到同样的问题。

下面的答案帮助我弄清楚了。 https://stackoverflow.com/a/33015901/9905202

【讨论】：