java发送内嵌图片邮件

要在Java中发送内嵌图片邮件，可以使用JavaMail API。以下是一个简单的示例代码：

import javax.activation.DataHandler;
import javax.activation.DataSource;
import javax.activation.FileDataSource;
import javax.mail.BodyPart;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.Multipart;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;
import javax.mail.internet.MimeUtility;

import java.util.Properties;

public class SendInlineImagesEmail {

    public static void main(String[] args) {

        // Recipient's email ID needs to be mentioned.
        String to = "recipient@example.com";

        // Sender's email ID needs to be mentioned
        String from = "sender@example.com";

        // Sender's email password needs to be mentioned
        String password = "password";

        // Assuming you are sending email through relay.jangosmtp.net
        String host = "relay.jangosmtp.net";

        // Get system properties
        Properties properties = System.getProperties();

        // Setup mail server
        properties.setProperty("mail.smtp.host", host);

        // Get the default Session object.
        Session session = Session.getDefaultInstance(properties);

        try {
            // Create a default MimeMessage object.
            MimeMessage message = new MimeMessage(session);

            // Set From: header field of the header.
            message.setFrom(new InternetAddress(from));

            // Set To: header field of the header.
            message.addRecipient(Message.RecipientType.TO, new InternetAddress(to));

            // Set Subject: header field
            message.setSubject("This is the subject");

            // Create the message part
            BodyPart messageBodyPart = new MimeBodyPart();

            // Fill the message
            messageBodyPart.setText("This is message body");

            // Create a multipart message
            Multipart multipart = new MimeMultipart();

            // Set text message part
            multipart.addBodyPart(messageBodyPart);

            // Part two is attachment
            messageBodyPart = new MimeBodyPart();
            String filename = "image.jpg";
            DataSource source = new FileDataSource(filename);
            messageBodyPart.setDataHandler(new DataHandler(source));
            messageBodyPart.setFileName(MimeUtility.encodeText(filename));
            messageBodyPart.setHeader("Content-ID", "<image>");

            // Add part two to multipart
            multipart.addBodyPart(messageBodyPart);

            // Send the complete message parts
            message.setContent(multipart);

            // Send message
            Transport.send(message);
            System.out.println("Sent message successfully....");
        } catch (MessagingException | UnsupportedEncodingException mex) {
            mex.printStackTrace();
        }
    }
}

在这个示例代码中，我们使用了两个 `MimeBodyPart` 对象来设置邮件正文和内嵌图片。我们在第二个 `MimeBodyPart` 中设置了图片的文件名和 Content-ID，Content-ID 的值可以在 HTML 中使用，来引用这个内嵌图片。在 HTML 中，内嵌图片的格式如下：

<img src="cid:image" alt="image"/>

注意，在发送邮件时，需要使用正确的邮箱账号和密码，并且要将 `host` 属性设置为正确的 SMTP 服务器地址。