javax.mailMimeMultipart发送空文本

Question

我正在使用javax.mail-1.6.2.jar，我制作了一个外部使用的类，我想在其中发送邮件。主要问题在代码的这一部分：

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.Properties;

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.AddressException;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;
import org.apache.log4j.Logger;
import org.json.JSONObject;

import main.java.caches.ServerCache;
import main.java.caches.servercache.MailConfig;

public class Mailer {
    
    private static final Logger LOG = Logger.getLogger(Mailer.class.getName());
  
    private static final String DEFAULTCONTENTTYPE = "text/html"; 
    
    private MailConfig mailConfig;
    private String mailSender;
    private String host;
    
    private String topic;
    private String message;
    private String contentType;
    private List<String> recipients = new ArrayList<>();
    private List<String> cc = new ArrayList<>();
    private List<String> bcc = new ArrayList<>();
    private List<File> attachments = new ArrayList<>();
    
    public Mailer() {
        Map<String, JSONObject> otherConfigs = ServerCache.getCache().getSysConf().getOtherConfigs();
        if(!otherConfigs.containsKey("MAIL")) {
            LOG.error("Keine Konfiguration für MAIL verfügbar");
            throw new RuntimeException();
        }
        mailConfig = ServerCache.getCache().getSysConf().getMailConfig();
        
        if(!mailConfig.isValid()) {
            LOG.error("MAIL Konfiguration unvollständig");
            throw new RuntimeException();
        }

        mailSender = mailConfig.getSender();
        host =  mailConfig.getServer();
        setContentType(DEFAULTCONTENTTYPE);
    }
    
    private Session getSessionForMail() {
        Properties properties = System.getProperties();
        properties.setProperty("mail.smtp.host", host);
        properties.put("mail.smtp.port", "25");     

        Session session = Session.getDefaultInstance(properties);
        return session;
    }
    
    public void sendeMail() {
        if(topic == null) {
            throw new RuntimeException("Betreff fehlt");
        }
        if(recipients.size() == 0) {
            throw new RuntimeException("Keine Empfänger");
        }
        
        try {
            Session session = getSessionForMail();
            Message mail = createMessage(session);
            
            Multipart mimeMultipart = makeMultipart();

            mail.setContent(mimeMultipart);
            mail.setContent(message , contentType);
            
            Transport.send(mail);

            LOG.info("Die Mail wurde an folgende Mailadresse(n) versandt: " + Arrays.toString(mail.getAllRecipients()));
        } catch (MessagingException mex) {
            LOG.error("Beim Versenden der Mail ist eine MessagingException aufgetreten: " + mex.getMessage(), mex);
        } 
    }

    private Multipart makeMultipart() throws MessagingException {
        Multipart mimeMultipart = new MimeMultipart();

        for (File a : attachments) {
            try {
                MimeBodyPart attachmentBodyPart = new MimeBodyPart();
                attachmentBodyPart.attachFile(a); 
                attachmentBodyPart.setFileName(a.getName()); 
                mimeMultipart.addBodyPart(attachmentBodyPart);

            } catch (IOException e) {
                LOG.error("Datei: " + a.getName() + "wurde nicht gefunden.");
            } 
        } 
        
        BodyPart textBodyPart = new MimeBodyPart();
        textBodyPart.setContent(message , contentType);
        mimeMultipart.addBodyPart(textBodyPart);

        return mimeMultipart;
    }

    private MimeMessage createMessage(Session session) throws AddressException, MessagingException {
        MimeMessage message = new MimeMessage(session);
        message.setFrom(new InternetAddress(mailSender));

        for (String r : recipients) {
            message.addRecipient(Message.RecipientType.TO, new InternetAddress(r)); 
        }
        
        for (String r : cc) {
            message.addRecipient(Message.RecipientType.CC, new InternetAddress(r)); 
        }
        
        for (String r : bcc) {
            message.addRecipient(Message.RecipientType.BCC, new InternetAddress(r)); 
        }
        message.setSubject(topic);
        
        return message;
    }

    public void setTopic(String topic) { this.topic = topic; }
    public void setMessage(String message) { this.message = message; }
    public void setRecipients(List<String> recipients) { this.recipients = recipients; }
    public void setAttachments(List<File> attachments) { this.attachments = attachments; }
    public void setCC(List<String> cc) { this.cc = cc; }
    public void setBCC(List<String> bcc) { this.bcc = bcc; }
    public void setContentType(String contentType) { this.contentType = contentType; }
}

在这个配置中，我在电子邮件中收到文本，因为我覆盖了mime内容。如果我删除mail.setContent（消息，contentType）；行，我的邮件将保持为空。所以contetnt类型和消息变量完全正常，只有Multipart无法正常工作。我在调试时看到，目前我设置了body part的内容，但内容为空，并且dh（datahandler）设置了一个对象。

编辑

现在你有了整个类。我认为举例子应该不是问题。设置文本或消息对象的内容很好，但如果我将multipart设置为消息对象的内容，文本将保持为空。

Answer 1

尝试替换方法中的以下代码

BodyPart textBodyPart = new MimeBodyPart();
textBodyPart.setContent(message , contentType);

具有

BodyPart textBodyPart = new MimeBodyPart();
((MimeBodyPart)textBodyPart).setText(message, contentType);