Sending Email Attachments using Spring Integration

Introduction

Here is a scenario I ran across recently, we had a customer who wanted us to process a series of files and place the contents into a relational database.  One of the requirements was that they wanted was to have a notification sent to their monitoring system (no big deal right).  When asked how they wanted us to send the notification, they said that they wanted it as an email notification with the result info in the attachment.  I was in a little shock assuming they would want it as an SNMP trap or Syslog etc. So as coding began there were no real discussion on email attachments using Spring Integration, so I decided to create one :).

The Message Flow

Figure1: Email Transformer and outbound mail adapter

So here we go, we see that 2 messageToMail transformers were created, one for success messages and the other for failed messages.  These could have been consolidated to one transformer, but I was experimenting.  Anyhow, we assume the processing of the file is complete and a status message has been sent to one of the messageToMail transformers.  The job of the transformer is to extract out the file name, status of the message and time finished then build up the email message.  Once the email message has been built it places it on to the outboundMail Channel in which the outbound mail adapter is listening.

For those who love the context xml here ya go:

<bean id="mailTransformerBean" class="com.concurrent.integration.EmailMessageTransformer">

<property name="mailTo" value="${email.mailTo}" />

<property name="mailFrom" value="${email.mailFrom}" />

<property name="mailSubject" value="${email.mailSubject}" />

<property name="mailHost" value="${email.mailHost}" />

<property name="attachmentName" value="${email.attachmentName}"/>

<property name="customer" value="${email.customer}"/>

<property name="processType" value="${email.processType}"/>

<property name="processName" value="${email.processName}"/>

<property name="processScript" value="${email.processScript}"/>

<property name="site" value="${email.site}"/>

</bean>

<bean id="mailSender" class="org.springframework.mail.javamail.JavaMailSenderImpl">

<property name="host" value="${email.mailHost}" />

<property name="port" value="${email.mailPort}" />

<property name="username" value="${email.mailUserName}" />

<property name="password" value="${email.password}" />

<property name="javaMailProperties">

<props>

<prop key="mail.smtp.auth">true</prop>

<prop key="mail.smtp.starttls.enable">true</prop>

</props>

</property>

</bean>

 <si:channel id="outboundMail" />

 <!-- Here's the Spring Integration flow -->

<si:channel id="mailSuccessNotice"/>

<si:channel id="mailFailNotice"/>

 <si:transformer id="messageToMailXFormSuccess" ref="mailTransformerBean" input-channel="mailSuccessNotice"

 method="transform" output-channel="outboundMail" />

 <si:transformer id="messageToMailXFormFail" ref="mailTransformerBean" input-channel="mailFailNotice"

 method="transform" output-channel="outboundMail" />

The Transformer Code!

So now to the important part, the transformer code that builds the email and inserts the attachement.

1. The code is broken into 5 sections:
2. Get the Message 
3. Build the MIME message
4. Extract message data
5. Build email and attachment
6. Send!!!!

Get the message
The transformer is associated with the mailSuccessNotice -or- mailFailNotice channel.  In either case the transform method is called.  Its first job is to extract the message payload and retrieve the mail text.

public MailMessage transform(Message<?> message) {

   Object payload = message.getPayload();

   String mailText = payload.toString();

Build the MIME message
The second thing the transformer does is to create the mime message object that will house the contents of the email.

JavaMailSenderImpl sender = new JavaMailSenderImpl();

sender.setHost(mailHost);

MimeMessage mimeMsg = sender.createMimeMessage();

MimeMailMessage msg = new MimeMailMessage(mimeMsg);

try {

   msg = new MimeMailMessage(new MimeMessageHelper(mimeMsg, true));

} catch (Exception e) {

   logger.warn("An email creation error occured because: "+          e.getMessage());

}

Extract message data

Now lets get the basic data from the mail text.  I created a method that would retrieve the information from the payload and generate a status message to be placed in the email. The code following is method signature:

String processStatus = parseMessagePayload(mailText,statusData);

This is the body of the method:

CSVParser parser = new CSVParser(new StringReader(payload));

String processStatus = null;

try {

String [] results = parser.getLine();

processStatus = results[0];

startTime = results[1];

endTime = results[2];

if(processStatus.equals("FAIL")){

     statusData.statusElement.description = "Process ended with "+results[3] 

             +"Warnings";

}else{

     statusData.statusElement.description = "Process ended Successfully"; }

} catch (Exception e) {

logger.error("Unable to parse message from processor.  Incomplete Email will be sent.");

}

return processStatus;

Build email and attachment

Now the transformer will build up the data for the mime message.

/* Create the mime message using spring.framework.mail packages */

MimeMessage mimeMsg = sender.createMimeMessage();

MimeMailMessage msg = new MimeMailMessage(mimeMsg);

try {

msg = new MimeMailMessage(new MimeMessageHelper(mimeMsg, true));

} catch (Exception e) {

logger.warn("An email creation error occured because: "+ e.getMessage());

}

msg.setTo(mailTo);

msg.setFrom(mailFrom);

msg.setSubject(mailSubject);

msg.setSentDate(new Date());

StatusData statusData = new StatusData();

/*Once the status message has been generated we create a Notification POJO and initialize it with the data.  

*/

Notification notification = new Notification();

notification.customer = customer;

notification.messageType = processType;

notification.site = site;

notification.processType = processType;

notification.processName = processName;

notification.processScript = processScript;

notification.processStartTime = startTime;

notification.processEndTime = endTime;

notification.processStatus = processStatus;

ProcessData processData = new ProcessData();

if(processStatus.equals("FAIL")){

processData.failData = statusData;

}else{

processData.successData = statusData;

}

notification.processData = processData;

String notificationString = "";

/** the user wants the data in XML format since it is being ingested by their ticket tracking system. */

try {

final JAXBContext jaxbContext = JAXBContext

.newInstance(Notification.class);

        StringWriter writer = new StringWriter();

jaxbContext.createMarshaller().marshal(notification, writer);

notificationString = writer.toString();

} catch (Exception ex) {

logger.error("Unable to create the attachment.  Incomplete Email will be sent.");

}

/** the body of the email contains the mail text plus the serialized content notification.

*/

msg.setText(mailText + " " + notificationString);

/**

The user has requested that we add the message as an attachment to the email.

*/

try {

msg.getMimeMessageHelper().addAttachment(attachmentName,

new ByteArrayResource(notificationString.getBytes()));

} catch (Exception e) {

logger.error("Unable to append attachment to email.  Incomplete Email will be sent.");

}

Send!!!
Now the message has been created.  It is routed to the outbound mail channel where it is then handled by the mailSender object as enumerated below.

<bean id="mailSender" class="org.springframework.mail.javamail.JavaMailSenderImpl">

<property name="host" value="${email.mailHost}" />

<property name="port" value="${email.mailPort}" />

<property name="username" value="${email.mailUserName}" />

<property name="password" value="${email.password}" />

<property name="javaMailProperties">

<props>

<prop key="mail.smtp.auth">true</prop>

<prop key="mail.smtp.starttls.enable">true</prop>

</props>

</property>

</bean>

Hope this helps out a little.   Please leave feedback.
Thanks,
--Glenn