E-mail MIME message parser

Question

As part of a larger Java application I'm working on, I have to retrieve emails and parse the data for the emails' content (subject, date, text, attachments, sender). In the method below, I pass a Message as a parameter, which is the Javamail abstract representation of an email. The details of the Message are recovered and then returned as a MailList. A MailList is just a holder for the five objects that describe each email.

public MailList getContent(Message message) throws MessagingException, IOException
{
 String body = "";
 String from = "";
 ArrayList<MimeBodyPart> attachments = new ArrayList<MimeBodyPart>(); 
 String contentType = message.getContentType();
 Address[] addresses = message.getFrom();
 if(addresses.length == 1)
 from = addresses[0].toString();
 else
 {
 for(int num = 0; num < addresses.length - 1; num++)
 from += addresses[num].toString() + ", ";
 from += addresses[addresses.length].toString();
 }
 if(contentType.contains("TEXT/PLAIN"))
 { 
 Object content = message.getContent();
 if(content != null)
 body += content.toString();
 }
 else if(contentType.contains("TEXT/HTML"))
 {
 Object content = message.getContent();
 if(content != null)
 body += Jsoup.parse((String)content).text();
 }
 else if(contentType.contains("multipart"))
 { 
 Multipart mp = (Multipart)message.getContent();
 int numParts = mp.getCount();
 for(int count = 0; count < numParts; count++)
 {
 MimeBodyPart part = (MimeBodyPart)mp.getBodyPart(count);
 String content = part.getContent().toString();
 if(MimeBodyPart.ATTACHMENT.equalsIgnoreCase(part.getDisposition()))
 attachments.add(part);
 else if(part.getContentType().contains("TEXT/HTML"))
 body += Jsoup.parse(content).text();
 else
 body += content;
 }
 }
 return new MailList(from, message.getSubject(), body,
 message.getSentDate().toString(), attachments);
}

This code works exactly as intended, but is very slow. Each method run can range from 0.5s to 1.5s depending on the content of the email. This means that parsing 10 emails might take up to 15s. Up to around 100 emails might be expected to be parsed at any given time, and 2 to 3 min is too long for such a process. Not sure if this could be improved to be more efficient but any advice is greatly appreciated.

Answer 1

if(addresses.length == 1)
 from = addresses[0].toString();
else
{
 for(int num = 0; num < addresses.length - 1; num++)
 from += addresses[num].toString() + ", ";
 from += addresses[addresses.length].toString();
} 

Concatenations of strings in a loop should be done using a StringBuilder like so

StringBuilder builder = new StringBuilder(1024);
for(int i = 0; i < addresses.length ; i++)
{
 builder.append(addresses[i].toString())
 .append(", ");
}
int builderLength = builder.length();
if(builderLength > 2)
{
 // removing the last appended ", "
 builder.setLength(builderLength - 2);
}
String from = builder.toString();

---

if(contentType.contains("TEXT/PLAIN"))
{ 
 Object content = message.getContent();
 if(content != null)
 body += content.toString();
}
else if(contentType.contains("TEXT/HTML"))
{
 Object content = message.getContent();
 if(content != null)
 body += Jsoup.parse((String)content).text();
} 

here it would be sufficient to just assign the content.toString() or Jsoup.parse((String)content).text() to the body variable. There is no need to use +=.

---

else if(contentType.contains("multipart"))
{ 
 Multipart mp = (Multipart)message.getContent();
 int numParts = mp.getCount();
 for(int count = 0; count < numParts; count++)
 {
 MimeBodyPart part = (MimeBodyPart)mp.getBodyPart(count);
 String content = part.getContent().toString();
 if(MimeBodyPart.ATTACHMENT.equalsIgnoreCase(part.getDisposition()))
 attachments.add(part);
 else if(part.getContentType().contains("TEXT/HTML"))
 body += Jsoup.parse(content).text();
 else
 body += content;
 }
} 

As mentioned above if you are using a loop for concatenations of strings this should be done using a StringBuilder.

You will only need the String content if the execution steps into the else if or else part and because one should declare variables as near to its usage, you could use continue; after the attachment is added like so

else if(contentType.contains("multipart"))
{ 
 StringBuilder bodyBuilder = new StringBuilder(1024);
 Multipart mp = (Multipart)message.getContent();
 int numParts = mp.getCount();
 for(int count = 0; count < numParts; count++)
 {
 MimeBodyPart part = (MimeBodyPart)mp.getBodyPart(count);
 if(MimeBodyPart.ATTACHMENT.equalsIgnoreCase(part.getDisposition()))
 {
 attachments.add(part);
 continue;
 }
 String content = part.getContent().toString();
 if(part.getContentType().contains("TEXT/HTML"))
 {
 bodyBuilder.append(Jsoup.parse(content).text());
 } else {
 bodyBuilder.append(content);
 }
 }
 body = bodyBuilder.toString();
} 

• connorp: Good suggestion with StringBuilder. All this shaved off about 200ms per email. Still slow but better than before. Thanks!

Answer 2

 if(addresses.length == 1)
 from = addresses[0].toString();
 else
 {

Don't omit the brackets around your if statements, funky things can happen later on if you mess those up. It's best to get in the habit of wrapping everything carefully.

if (adresses.length == 1) {
 from = adresses[0].toString();
} else {

---

I would suggest replacing the following for loop with an array joiner.

 for(int num = 0; num < addresses.length - 1; num++)
 from += addresses[num].toString() + ", ";
 from += addresses[addresses.length].toString();

You could try StringUtils.join or Collectors.joining (Java 8)

---

In both .contains("TEXT/HTML") and .contains("TEXT/PLAIN") the executions are very similar, so, you could consider combining them, and splitting the possible pathways at body +=

---

Instead of:

int numParts = mp.getCount();
for(int count = 0; count < numParts; count++)

You could declare numParts inside the for loop, like so:

for(int count = 0, numParts = mp.getCount(); count < numParts; count++)

• bunyaCloven: @connorp not that you can do it in java, but looking at goto fail bug of apple will help why it is a good practice not to omit parentheses

Answer 3

I would suggest you use email-mime-parser,

Following sample code gives you all the relevant info you need:

ContentHandler contentHandler = new CustomContentHandler();
MimeConfig mime4jParserConfig = new MimeConfig();
BodyDescriptorBuilder bodyDescriptorBuilder = new DefaultBodyDescriptorBuilder();
MimeStreamParser mime4jParser = new MimeStreamParser(mime4jParserConfig,DecodeMonitor.SILENT,bodyDescriptorBuilder);
mime4jParser.setContentDecoding(true);
mime4jParser.setContentHandler(contentHandler);
InputStream mailIn = 'Provide email mime stream here';
mime4jParser.parse(mailIn);
Email email = ((CustomContentHandler) contentHandler).getEmail();
List<Attachment> attachments = email.getAttachments();
Attachment calendar = email.getCalendarBody();
Attachment htmlBody = email.getHTMLEmailBody();
Attachment plainText = email.getPlainTextEmailBody();
String to = email.getToEmailHeaderValue();
String cc = email.getCCEmailHeaderValue();
String from = email.getFromEmailHeaderValue();