关于Java：如何使用InputStream和Spring发送带有附件的电子邮件？

How to send email with attachment using InputStream and Spring?

情况是这样的：

首先，我们在内存中生成一个文件，我们可以得到一个InputStream对象。
其次，InputStream对象必须作为电子邮件的附件发送。语言是Java，我们使用Spring发送电子邮件。

我发现了很多信息，但是找不到使用InputStream发送电子邮件附件的方法。我尝试这样做：

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InputStreamSource iss= new InputStreamResource(new FileInputStream("c:\\\\a.txt"));
MimeMessageHelper message = new MimeMessageHelper(mimeMessage, true,"UTF-8");
message.addAttachment("attachment", iss);

但我有一个例外：

Passed-in Resource contains an open stream: invalid argument. JavaMail
requires an InputStreamSource that creates a fresh stream for every
call.

相关讨论

您可以根据需要对InputStreamSource进行简单实现，并在其中传递新鲜的InputStream：

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InputStreamSource iss = new InputStreamSource() {
@Override
public InputStream getInputStream() throws IOException {
// provide fresh InputStream
return new FileInputStream("c:\\\\a.txt");
}
}
MimeMessageHelper message = new MimeMessageHelper(mimeMessage, true,"UTF-8");
message.addAttachment("attachment", iss);

工作示例是：

1)附件是InputStreamSource接口

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public void send() throws IOException, MessagingException {
final ByteArrayOutputStream stream = createInMemoryDocument("body");
final InputStreamSource attachment = new ByteArrayResource(stream.toByteArray());
final MimeMessage message = javaMailSender.createMimeMessage();
final MimeMessageHelper helper = new MimeMessageHelper(message, true);
helper.setSubject("subject");
helper.setFrom("[email protected]");
helper.setTo("[email protected]");
helper.setReplyTo("[email protected]");
helper.setText("stub", false);
helper.addAttachment("document.txt", attachment);
javaMailSender.send(message);
}

2)附件是DataSource接口

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public void send() throws IOException, MessagingException {
final ByteArrayOutputStream document = createInMemoryDocument("body");
final InputStream inputStream = new ByteArrayInputStream(document.toByteArray());
final DataSource attachment = new ByteArrayDataSource(inputStream,"application/octet-stream");
final MimeMessage message = javaMailSender.createMimeMessage();
final MimeMessageHelper helper = new MimeMessageHelper(message, true);
helper.setSubject("subject");
helper.setFrom("[email protected]");
helper.setTo("[email protected]");
helper.setReplyTo("[email protected]");
helper.setText("stub", false);
helper.addAttachment("document.txt", attachment);
javaMailSender.send(message);
}

说明：

Passed-in Resource contains an open stream: invalid argument.
JavaMail requires an InputStreamSource that creates a fresh stream for
every call.

如果开发人员使用InputStreamSource的实现在isOpen()方法中返回true，则可能会出现此消息。

方法MimeMessageHelper#addAttacment()中有一个特殊检查：

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public void addAttachment(String attachmentFilename, InputStreamSource inputStreamSource, String contentType) {
//...
if (inputStreamSource instanceof Resource && ((Resource) inputStreamSource).isOpen()) {
throw new IllegalArgumentException(
"Passed-in Resource contains an open stream: invalid argument." +
"JavaMail requires an InputStreamSource that creates a fresh stream for every call.");
}
//...
}

InputStreamResource#isOpen()总是返回true，这使得无法将此实现用作附件：

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public class InputStreamResource extends AbstractResource {
//...
@Override
public boolean isOpen() {
return true;
}
//...
}

// inlineFileObjectCreated-您可以创建一个StringBuilder对象作为示例

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ByteArrayDataSource source = new ByteArrayDataSource("file name","contentType", inlineFileObjectCreated.getBytes() );

JavaMailSender mailSender = (JavaMailSender) ServicesHome.getService("javaMailSender");
MimeMessage mimeMessage = mailSender.createMimeMessage();
MimeMessageHelper mimeMessageHelper = new MimeMessageHelper(mimeMessage, true);
mimeMessageHelper.setTo(toArray);
mimeMessageHelper.setSubject("");
mimeMessageHelper.setText("");
mimeMessageHelper.addAttachment("filename", source);
mailSender.send(mimeMessageHelper.getMimeMessage());

//////////////////////////////////////////////////

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import javax.activation.DataSource;

public class ByteArrayDataSource implements DataSource {
byte[] bytes;
String contentType;
String name;

public ByteArrayDataSource( String name, String contentType, byte[] bytes ) {
this.name = name;
this.bytes = bytes;
this.contentType = contentType;
}

public String getContentType() {
return contentType;
}

public InputStream getInputStream() {
return new ByteArrayInputStream(bytes);
}

public String getName() {
return name;
}

public OutputStream getOutputStream() throws IOException {
throw new FileNotFoundException();
}
}