javaMail 奇怪的NullPointerException

环境：spring-framework-4.0.6.RELEASE，javamail-1.4.5，xheditor-1.1.14

调用org.springframework.mail.javamail.JavaMailSenderImpl.send(MimeMessage mimeMessage) throws MailException产生的异常：

Exception in thread "main" Java.lang.NullPointerException at javax.mail.internet.MimeUtility.getEncoding(MimeUtility.java:226) at javax.mail.internet.MimeUtility.getEncoding(MimeUtility.java:299) at javax.mail.internet.MimeBodyPart.updateHeaders(MimeBodyPart.java:1375) at javax.mail.internet.MimeBodyPart.updateHeaders(MimeBodyPart.java:1021) at javax.mail.internet.MimeMultipart.updateHeaders(MimeMultipart.java:419) at javax.mail.internet.MimeBodyPart.updateHeaders(MimeBodyPart.java:1354)

原因：url的网络资源获取不到产生的

if(url.matches("\\w+:.+")) {    //网络文件    LogUtil.printLog(url);    DataSource dataSource = new URLDataSource(new URL(url));     try {         //here will be exception, if can't get net resource        dataSource.getInputStream();    } catch (IOException e) {        e.printStackTrace();        return ;    }

例子：

class SendMail {    private int isEmail;    void sendMail(){        if(1==isEmail) {            UserEmail userEmail=userDao.loadUserEmail(SystemContext.getLoginUser().getId());            List<String> userEmails=userDao.listEmailList(userId);            taskExecutor.execute(new SendMailThread(message, userEmails, attachmentDto, newName, uploadPath, userEmail));        }    }    private class SendMailThread implements Runnable {        //need send message        private Message message;        //need send to the emails        List<String> emails;        //attachments with the email        private AttachmentDto attachmentDto;        private String[] newNames;        //the local resource path        private String path;        //the sender email        private UserEmail userEmail;        public SendMailThread(Message message, List<String> emails, AttachmentDto attachmentDto, String[] newNames,                String path, UserEmail userEmail) {            this.message = message;            this.emails = emails;            this.attachmentDto = attachmentDto;            this.newNames = newNames;            this.path = path;            this.userEmail=userEmail;        }        @Override        public void run() {            try {                SendMail();            } catch (UnsupportedEncodingException | MessagingException | MalformedURLException e) {                e.printStackTrace();            }        }        private void SendMail() throws UnsupportedEncodingException, MessagingException, MalformedURLException {            //创建一个JavaMailSenderImpl, 根据用户设置数据            LogUtil.printLog("start to send email!");            JavaMailSenderImpl jmSenderImpl=(JavaMailSenderImpl)mailSender;            jmSenderImpl.setHost(userEmail.getHost());            jmSenderImpl.setProtocol(userEmail.getProtocol());            jmSenderImpl.setUsername(userEmail.getUsername());            jmSenderImpl.setPassword(userEmail.getPassword());            MimeMessage email=jmSenderImpl.createMimeMessage();            MimeMessageHelper helper=new MimeMessageHelper(email, true, "utf-8");            helper.setFrom(userEmail.getUsername());            //获取要发送用户的邮件            for(String emailTo: emails) {                helper.addTo(emailTo);            }            helper.setSubject(MimeUtility.encodeText(message.getTitle()));            if(attachmentDto.isHasAttachment()) {                File[] attachments=attachmentDto.getAttachments();                String[] fileNames=attachmentDto.getAttachmentsFilename();                for(int i=0; i<attachments.length; ++i) {                    File file=new File(path+File.separator+newNames[i]);                    String name=fileNames[i];                    helper.addAttachment(MimeUtility.encodeText(name), file);                }            }            //格式化内容            String content=message.getContent();            LogUtil.printLog(content);            //一、            //必须先设置好内容的值，之后再设置相应的附件，否则最后一个图片不会替换，所以不会显示;            //helper.setText(MimeUtility.encodeText(content), true);            //List<String> imgSrcs=listContentImgUrl(content);            //for(String src: imgSrcs) {            //  String cid=FilenameUtils.getBaseName(src)+System.currentTimeMillis()+"."+FilenameUtils.getExtension(src);            //  //注意先添加content到MessageHelper中， 再添加dataSource，才能查找到            //  content=content.replace(src, "cid:"+cid);            //  URLDataSource dataSource=null;            //  try {            //      dataSource = new URLDataSource(new URL(src));            //  } catch (MalformedURLException e) {            //      e.printStackTrace();            //  }            //  helper.addInline(cid, dataSource);            //}            //二、            //建议先把内容设置好，之后再来一次性的添加附件            List<String> imgSrcs=listContentImgUrl(content);            Map<String, String> cidImgMap=new HashMap<>();            int i=0;            //替换content内容为cid            for(String src: imgSrcs) {                String cid="image_"+(++i);                //注意先添加content到MessageHelper中， 再添加dataSource，才能查找到                if(src.matches("\\w+:.+")) {                    //网络文件                    LogUtil.printLog(src);                    DataSource dataSource = new URLDataSource(new URL(src));                    //get network resource stream，if exception that show it is not available                     try {                        dataSource.getInputStream();                        content=content.replace(src, "cid:"+cid);                        cidImgMap.put(cid, src);                    } catch (IOException e) {                        e.printStackTrace();                        LogUtil.printLog("can't get network resource!!:"+src);                    }                }else {                    content=content.replace(src, "cid:"+cid);                    cidImgMap.put(cid, src);                }            }            helper.setText(content, true);            //添加cid的dataSource            //如果是服务器上的图片，不以http等协议开头的，应该获取文件路径，然后通过FileSystemResource来获取            for(Iterator<String> iterator=cidImgMap.keySet().iterator(); iterator.hasNext(); ) {                String cid=iterator.next();                String url=cidImgMap.get(cid);                LogUtil.printLog(cid+": "+url);                if(url.matches("\\w+:.+")) {                    //网络文件                    LogUtil.printLog(url);                    DataSource dataSource = new URLDataSource(new URL(url));                     try {                        dataSource.getInputStream();                    } catch (IOException e) {                        e.printStackTrace();                        return ;                    }                    helper.addInline(cid, dataSource);                }else {                    //本地文件                    LogUtil.printLog(path+File.separator+".."+File.separator+url);                    File file=new File(path+File.separator+".."+File.separator+url);                    if(!file.exists()) {                        throw new RuntimeException(file.getAbsolutePath()+" isn't exist!");                    }                    LogUtil.printLog(file.length());                    FileSystemResource fsr=new FileSystemResource(path+File.separator+".."+File.separator+url);                    helper.addInline(cid, fsr);                }            }            LogUtil.printLog(content);            jmSenderImpl.send(email);            LogUtil.printLog("email send Successful=============================");        }        //get image source list by regExp        private List<String> listContentImgUrl(String content){            Pattern pattern=Pattern.compile("<img[^>]*\\s{1,}src\\s{0,}=\\s{0,}\\\\?['\"]([^'\"]+)\\\\?['\"]");            Matcher matcher=pattern.matcher(content);            List<String> imgUrlList=new ArrayList<>();            while(matcher.find()) {                imgUrlList.add(matcher.group(1));            }            return imgUrlList;        }    }}