Message channels one or many? - email

Question

I need to handle emails from about 30 addresses. I implement this in a way where all emails going to one DirectChannel and after to Receiver. In Receiver I can understand from what address is message comes, to do this I create CustomMessageSource that wraps javax.mail.Message to my own type that contains javax.mail.Message and some Enum. Looks like this is not a good decision, cause I can use #Transformer, but how can I use it if I have only 1 channel?
That was the first question.
Second question:
Should I use ONE channel and ONE receiver for all that addresses? Or better to have channel and receiver for each mail address? I don't understand Spring so deeply to feel the difference.
p.s. this question is continuation of Spring multiple imapAdapter

Answer 1

In each child context, you can add a header enricher to set a custom header to the URL from the adapter; with the output channel being the shared channel to the shared service.
In the service, use void foo(Message emailMessage, #Header("myHeader") String url)
I would generally recommend using a single service unless the service needs to do radically different things based on the source.
EDIT:
I modified my answer to your previous question to enhance the original message with the url in a header; each instance has its own header enricher and they all route the enriched message to the common emailChannel.
#Configuration
#EnableIntegration
public class GeneralImapAdapter {
#Value("${imap.url}")
String imapUrl;
#Bean
public static PropertySourcesPlaceholderConfigurer pspc() {
return new PropertySourcesPlaceholderConfigurer();
}
#Bean
#InboundChannelAdapter(value = "enrichHeadersChannel", poller = #Poller(fixedDelay = "10000") )
public MessageSource<javax.mail.Message> mailMessageSource(MailReceiver imapMailReceiver) {
return new MailReceivingMessageSource(imapMailReceiver);
}
#Bean
public MessageChannel enrichHeadersChannel() {
return new DirectChannel();
}
#Bean
#Transformer(inputChannel="enrichHeadersChannel", outputChannel="emailChannel")
public HeaderEnricher enrichHeaders() {
Map<String, ? extends HeaderValueMessageProcessor<?>> headersToAdd =
Collections.singletonMap("emailUrl", new StaticHeaderValueMessageProcessor<>(this.imapUrl));
HeaderEnricher enricher = new HeaderEnricher(headersToAdd);
return enricher;
}
#Bean
public MailReceiver imapMailReceiver() {
MailReceiver receiver = mock(MailReceiver.class);
Message message = mock(Message.class);
when(message.toString()).thenReturn("Message from " + this.imapUrl);
Message[] messages = new Message[] {message};
try {
when(receiver.receive()).thenReturn(messages);
}
catch (MessagingException e) {
e.printStackTrace();
}
return receiver;
}
}
...and I modified the receiving service so it gets access to the header...
#MessageEndpoint
public class EmailReceiverService {
#ServiceActivator(inputChannel="emailChannel")
public void handleMessage(Message message, #Header("emailUrl") String url) {
System.out.println(message + " header:" + url);
}
}
...hope that helps.
EDIT 2:
And this one's a bit more sophisticated; it pulls the from from the payload and puts it in a header; not needed for your use case since you have the full message, but it illustrates the technique...
#Bean
#Transformer(inputChannel="enrichHeadersChannel", outputChannel="emailChannel")
public HeaderEnricher enrichHeaders() {
Map<String, HeaderValueMessageProcessor<?>> headersToAdd = new HashMap<>();
headersToAdd.put("emailUrl", new StaticHeaderValueMessageProcessor<String>(this.imapUrl));
Expression expression = new SpelExpressionParser().parseExpression("payload.from[0].toString()");
headersToAdd.put("from", new ExpressionEvaluatingHeaderValueMessageProcessor<>(expression, String.class));
HeaderEnricher enricher = new HeaderEnricher(headersToAdd);
return enricher;
}
and
#ServiceActivator(inputChannel="emailChannel")
public void handleMessage(Message message, #Header("emailUrl") String url,
#Header("from") String from) {
System.out.println(message + " header:" + url + " from:" + from);
}