Spring Integration - Dynamic MailReceiver configuration - spring

Question

I'm pretty new to spring-integration anyway I'm using it in order to receive mails and elaborate them.
I used this spring configuration class:
#Configuration
#EnableIntegration
#PropertySource(value = { "classpath:configuration.properties" }, encoding = "UTF-8", ignoreResourceNotFound = false)
public class MailReceiverConfiguration {
private static final Log logger = LogFactory.getLog(MailReceiverConfiguration.class);
#Autowired
private EmailTransformerService emailTransformerService;
// Configurazione AE
#Bean
public MessageChannel inboundChannelAE() {
return new DirectChannel();
}
#Bean(name= {"aeProps"})
public Properties aeProps() {
Properties javaMailPropertiesAE = new Properties();
javaMailPropertiesAE.put("mail.store.protocol", "imap");
javaMailPropertiesAE.put("mail.debug", Boolean.TRUE);
javaMailPropertiesAE.put("mail.auth.debug", Boolean.TRUE);
javaMailPropertiesAE.put("mail.smtp.socketFactory.fallback", "false");
javaMailPropertiesAE.put("mail.imap.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
return javaMailPropertiesAE;
}
#Bean(name="mailReceiverAE")
public MailReceiver mailReceiverAE(#Autowired MailConfigurationBean mcb, #Autowired #Qualifier("aeProps") Properties javaMailPropertiesAE) throws Exception {
return ConfigurationUtil.getMailReceiver("imap://USERNAME:PASSWORD#MAILSERVER:PORT/INBOX", new BigDecimal(2), javaMailPropertiesAE);
}
#Bean
#InboundChannelAdapter( autoStartup = "true",
channel = "inboundChannelAE",
poller = {#Poller(fixedRate = "${fixed.rate.ae}",
maxMessagesPerPoll = "${max.messages.per.poll.ae}") })
public MailReceivingMessageSource pollForEmailAE(#Autowired MailReceiver mailReceiverAE) {
MailReceivingMessageSource mrms = new MailReceivingMessageSource(mailReceiverAE);
return mrms;
}
#Transformer(inputChannel = "inboundChannelAE", outputChannel = "transformerChannelAE")
public MessageBean transformitAE( MimeMessage mailMessage ) throws Exception {
// amministratore email inbox
MessageBean messageBean = emailTransformerService.transformit(mailMessage);
return messageBean;
}
#Splitter(inputChannel = "transformerChannelAE", outputChannel = "nullChannel")
public List<Message<?>> splitIntoMessagesAE(final MessageBean mb) {
final List<Message<?>> messages = new ArrayList<Message<?>>();
for (EmailFragment emailFragment : mb.getEmailFragments()) {
Message<?> message = MessageBuilder.withPayload(emailFragment.getData())
.setHeader(FileHeaders.FILENAME, emailFragment.getFilename())
.setHeader("directory", emailFragment.getDirectory()).build();
messages.add(message);
}
return messages;
}
}
So far so good.... I start my micro-service and there is this component listening on the specified mail server and mails are downloaded.
Now I have this requirement: mail server configuration (I mean the string "imap://USERNAME:PASSWORD#MAILSERVER:PORT/INBOX") must be taken from a database and it can be configurable. In any time a system administrator can change it and the mail receiver must use the new configuration.
As far as I understood I should create a new instance of MailReceiver when a new configuration is present and use it in the InboundChannelAdapter
Is there any best practice in order to do it? I found this solution: ImapMailReceiver NO STORE attempt on READ-ONLY folder (Failure) [THROTTLED];
In this solution I can inject the ThreadPoolTaskScheduler if I define it in my Configuration class; I can also inject the DirectChannel but every-time I should create a new MailReceiver and a new ImapIdleChannelAdapter without considering this WARN message I get when the
ImapIdleChannelAdapter starts:
java.lang.RuntimeException: No beanfactory at org.springframework.integration.expression.ExpressionUtils.createStandardEvaluationContext(ExpressionUtils.java:79) at org.springframework.integration.mail.AbstractMailReceiver.onInit(AbstractMailReceiver.java:403)
Is there a better way to satisfy my scenario?
Thank you
Angelo

Answer 1

The best way to do this is to use the Java DSL and dynamic flow registration.
Documentation here.
That way, you can unregister the old flow and register a new one, each time the configuration changes.
It will automatically handle injecting dependencies such as the bean factory.