如何使用outputstream在java中添加附件到电子邮件

我已经看到了javax.mail库的代码，你可以在其中添加附件到电子邮件：

MimeBodyPart attachmentPart = new MimeBodyPart(); FileDataSource fds = new FileDataSource("C:/text.txt"); attachmentPart.setDataHandler(new DataHandler(fds)); attachmentPart.setFileName("text.txt"); multipart.addBodyPart(attachmentPart); 

但这需要该文件驻留在此磁盘上的某个位置。 我想直接从电子邮件库中获取一个输出流，并直接从我写入该输出流的另一个地方将文件内容流入其中。 这可能吗？

Answer 1

尝试使用ByteArrayDataSource，就像这样

 ByteArrayOutputStream baos = //Read the output stream DataSource aAttachment = new ByteArrayDataSource(baos.toByteArray(),"application/octet-stream"); MimeBodyPart attachmentPart = new MimeBodyPart(); attachmentPart.setDataHandler(new DataHandler(aAttachment)); 

Answer 2

是的，这是可能的。 使用ByteArrayDataSource的答案并不能为大型附件提供令人满意的解决方案，因为它要求整个内容一次驻留在内存中。 更好的解决方案是使用由PipedInputStream提供的DataHandler，而PipedInputStream又由PipedOutputStream写入。 当然，这需要第二个线程。 下面的代码演示了这一点：

 import com.sun.mail.smtp.*; import java.io.InputStream; import java.io.IOException; import java.io.PrintWriter; import java.io.OutputStream; import java.io.OutputStreamWriter; import java.io.PipedInputStream; import java.io.PipedOutputStream; import java.util.Date; import java.util.Properties; import javax.activation.DataHandler; import javax.activation.DataSource; import javax.mail.*; import javax.mail.internet.*; public class javamail { // Piped Data Source private static class PipedDataSource implements DataSource { InputStream in; String type; public PipedDataSource (InputStream in, String type) { this.in = in; this.type = type; } public String getContentType() { return type; } public InputStream getInputStream() { return in; } public String getName() { return "DataSource"; } public OutputStream getOutputStream() throws IOException { throw new IOException("No OutputStream"); } } // Main Method public static void main(String [] args) throws Exception { final int BUFFER_SIZE = 32768; Properties properties = new Properties(); properties.put("mail.smtp.starttls.enable", System.getProperty("mail.smtp.starttls.enable","true")); properties.put("mail.smtp.ssl.trust", System.getProperty("mail.smtp.ssl.trust","*")); properties.put("mail.smtp.host", System.getProperty("mail.smtp.host","localhost")); properties.put("mail.smtp.port", System.getProperty("mail.smtp.port","587")); Session session = Session.getInstance(properties); String host = properties.getProperty("mail.smtp.host"); int port = Integer.parseInt(properties.getProperty("mail.smtp.port")); System.err.println("connect: smtp://"+host+":"+port); System.err.flush(); MimeMessage msg = new MimeMessage(session); PipedInputStream in = new PipedInputStream(BUFFER_SIZE); PipedOutputStream out = new PipedOutputStream(in); // Set general headers msg.setFrom(System.getProperty("mail.from","Unknown ")); msg.setRecipients(Message.RecipientType.TO, System.getProperty("mail.to", "[e-mail]")); msg.setSentDate(new Date()); msg.setSubject("JavaMail Test"); msg.setHeader("X-Mailer", "JavaMail"); // Set main text - Part 1 - content provided here MimeBodyPart part1 = new MimeBodyPart(); StringBuilder sb = new StringBuilder(); sb.append("This is the cover letter that describes the accompanying \n"); sb.append("attachment, which is a base64 encoded text document of \n"); sb.append("little more value than a demonstration.\n\n"); part1.setText(sb.toString()); // Writes a computed Content-Type Header part1.setHeader("Content-Type","text/plain; charset=us-ascii; format=flowed; delsp=yes"); // Rewrite Header // Set attachment - Part 2 - content provdied from another thread via a pipe MimeBodyPart part2 = new MimeBodyPart(); part2.setDataHandler(new DataHandler(new PipedDataSource (in, "text/html"))); // Writes a Content-Type Header part2.setHeader("Content-Type","text/plain; charset=\"utf-8\"; name=\"Lorem Ipsum.txt\""); // Rewrite Header part2.setHeader("Content-Disposition", "attachment; filename=\"Lorem Ipsum.txt\""); part2.setHeader("Content-Transfer-Encoding","base64"); // Join parts MimeMultipart multipart = new MimeMultipart(); multipart.addBodyPart(part1); multipart.addBodyPart(part2); msg.setContent(multipart); // Start thread to deliver content for Part 2 attachment via DataHandler Thread t = new Thread() { public void run() { try { PrintWriter w = new PrintWriter(new OutputStreamWriter(out,"UTF-8")); w.print("Lorem ipsum dolor sit amet, ligula suspendisse nulla pretium"); w.print(", rhoncus tempor fermentum, enim integer ad vestibulum volut"); w.print("pat. Nisl rhoncus turpis est, vel elit, congue wisi enim nun"); w.print("c ultricies sit, magna tincidunt. Maecenas aliquam maecenas "); w.print("ligula nostra, accumsan taciti. Sociis mauris in integer, a "); w.print("dolor netus non dui aliquet, sagittis felis sodales, dolor s"); w.print("ociis mauris, vel eu libero cras. Faucibus at. Arcu habitass"); w.print("e elementum est, ipsum purus pede porttitor class, ut adipis"); w.print("cing, aliquet sed auctor, imperdiet arcu per diam dapibus li"); w.print("bero duis. Enim eros in vel, volutpat nec pellentesque leo, "); w.print("temporibus scelerisque nec."); w.println(""); w.println(""); w.flush(); // Ensure data completely flushed to buffer w.close(); // closes the writer and PipedOutputStream } catch(Exception e) { e.printStackTrace(); }; try { out.close(); } catch(Exception e) { e.printStackTrace(); } } }; t.start(); // Send the message on its way SMTPTransport xp = (SMTPTransport) session.getTransport(); xp.connect(); xp.sendMessage(msg,msg.getAllRecipients()); System.err.println(xp.getLastServerResponse()); t.join(); return; } } 

您可以使用命令行中定义的以下属性（根据需要进行编辑）运行此代码：

 -Dmail.from="[e-mail]" -Dmail.to="[e-mail]" -Dmail.smtp.host=smtp.example.com -Dmail.smtp.port=587 or 25 

示例代码使用us-ascii编码发送带有文本/普通封面信函的电子邮件，并使用带有base64传输编码的utf-8编码发送文本/普通附件。 如果MX支持，它还使用STARTTLS（加密传输）。