使用JavaMail发送邮件-no object DCH for MIME type multipart/mixed报错解决

MailcapCommandMap mc = (MailcapCommandMap) CommandMap.getDefaultCommandMap();
mc.addMailcap("text/html;; x-java-content-handler=com.sun.mail.handlers.text_html");
mc.addMailcap("text/xml;; x-java-content-handler=com.sun.mail.handlers.text_xml");
mc.addMailcap("text/plain;; x-java-content-handler=com.sun.mail.handlers.text_plain");
mc.addMailcap("multipart/*;; x-java-content-handler=com.sun.mail.handlers.multipart_mixed; x-java-fallback-entry=true");
mc.addMailcap("message/rfc822;; x-java-content-handler=com.sun.mail.handlers.message_rfc822");
CommandMap.setDefaultCommandMap(mc);                        
Thread.currentThread().setContextClassLoader( getClass().getClassLoader() );        

package TestMailSend;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Properties;
import javax.activation.DataHandler;
import javax.activation.FileDataSource;
import javax.mail.Message;
import javax.mail.MessagingException;
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;

public class SendMail {

    public static void main(String[] args) throws Exception{
        //创建Properties文件
        Properties prop=new Properties();
        prop.setProperty("mail.host", "mail.boe.com.cn");//主机
        prop.setProperty("mail.transport.protocol", "smtp");
        prop.setProperty("mail.smtp.auth", "true");
        //使用JavaMail发送邮件的5个step
        //step1 创建session
        //Session session=Session.getInstance(prop);
        Session session1=Session.getDefaultInstance(prop);
        //开启session的debug模式，可以看到程序发送email的运行状态
        session1.setDebug(true);
        //step2 通过session得到transport对象
        //Transport trans=session.getTransport();
        Transport trans=session1.getTransport();        
        //step3 使用邮件的用户名和密码连上邮箱服务器，发送邮件时，需要验证发件人的邮箱名和密码正确后才可以发送
        trans.connect("mail.boe.com.cn", "发件人邮箱", "发件人邮箱密码");
        //step4 创建邮件
        //Message message=createSimpleMail(session);//发送纯文本
        Message messageAttach=createAttachMail(session1);
        //step5 发送邮件
        
        //trans.sendMessage(message, message.getAllRecipients());
        trans.sendMessage(messageAttach, messageAttach.getAllRecipients());
        trans.close();
    }
    /**
     * 创建一个封只包含文本的邮件
     * @param session
     * @return
     * @throws MessagingException 
     * @throws AddressException 
     */
    public static MimeMessage createSimpleMail(Session session) throws AddressException, MessagingException{
        //创建邮箱对象
        MimeMessage message=new MimeMessage(session);
        //指明邮件的发件人
        message.setFrom(new InternetAddress("发件人邮箱"));
        //指明邮件的收件人
        message.setRecipient(Message.RecipientType.TO, new InternetAddress("收件人邮箱"));
        //邮件的标题
        message.setSubject("只包含文本的简单邮件");
        //邮件的文本内容
        message.setContent("这是一封测试邮件！","text/html;charset=utf-8");
        //返回创建好的邮件对象
        return message;
    }
    /**
     * 创建一封包含附件的邮件
     * @param session
     * @return
     * @throws MessagingException 
     * @throws AddressException 
     * @throws IOException 
     * @throws FileNotFoundException 
     */
    public static MimeMessage createAttachMail(Session session) throws AddressException, MessagingException, FileNotFoundException, IOException{
        //创建邮件
        MimeMessage message=new MimeMessage(session);
        //指明邮件发件人
        message.setFrom(new InternetAddress("发件人邮箱"));
        //指明邮件收件人
        message.setRecipient(Message.RecipientType.TO, new InternetAddress("收件人邮箱"));
        //邮件标题
        message.setSubject("这是一封包含附件的邮件");    
        
        //创建邮件正文，为了避免邮件正文中文乱码，使用utf-8
        MimeBodyPart text=new MimeBodyPart();
        text.setContent("使用JavaMail创建的包含附件的邮件","application/x-xls;charset=utf-8");
        
        //创建附件邮件
        MimeBodyPart attachment=new MimeBodyPart();
        DataHandler dh=new DataHandler(new FileDataSource("C:\\测试Excel.xls"));
        attachment.setDataHandler(dh);
        attachment.setFileName(dh.getName());
        
        //创建容器描述数据关系
        MimeMultipart mmp=new MimeMultipart();
        mmp.addBodyPart(text);
        mmp.addBodyPart(attachment);
        mmp.setSubType("mixed");
        
        message.setContent(mmp);
        message.saveChanges();
        //存盘
        message.writeTo(new FileOutputStream("C:\\attachmentEmail.eml"));
        //返回生成的邮件
        return message;
    }

}