Apache Camel: The mail message does not have any recipients set

Question

camel-context.xml

<route id="mail-route-imap" autoStartup="true">
    <!-- Trigger the route using a timer -->
    <from uri="timer://loadEmailParams?period=10000" />

    <!-- Process the bean to fetch IMAP URL and Port -->
    <process ref="emailConfigProcessor" />

    <!-- Log the dynamic properties -->
    <log message="Fetching from IMAP URL: ${exchangeProperty.imapUrl}, Port: ${exchangeProperty.imapPort}" />

    <!-- Fetch emails dynamically using toD for IMAP -->
    <toD uri="imaps://${exchangeProperty.imapUrl}:${exchangeProperty.imapPort}?authenticator=#exchangeAuthenticator&amp;mail.imaps.auth.mechanisms=XOAUTH2&amp;searchTerm=#customSearchTerm" />

    <!-- Log the successful fetching of emails -->
    <log message="Fetched emails from ${exchangeProperty.imapUrl}" />
</route>

Processor:

@Component
public class EmailConfigProcessor implements Processor {

    @Autowired
    private EmailConfigBean emailConfigBean;

    @Override
    public void process(Exchange exchange) throws Exception {
        exchange.setProperty("imapUrl", emailConfigBean.getImapUrl());
        exchange.setProperty("imapPort", emailConfigBean.getImapPort());
    }
}

EmailConfigBean

@Component("emailConfigBean")
public class EmailConfigBean {
    public String getImapUrl() {
        return "myoutlook.com";  // Example IMAP URL
    }

    public String getImapPort() {
        return "993";  // Example IMAP Port
    }
}

Error:

java.lang.IllegalArgumentException: The mail message does not have any recipients set.
    at org.apache.camel.component.mail.MailBinding.populateMailMessage(MailBinding.java:157)

Alternative approach tried with :

<route id="mail-route-imap" autoStartup="true">
    <!-- Set properties for IMAP URL and port from EmailConfigBean -->
    <process ref="emailConfigProcessor" />

    <!-- Log the properties for debugging -->
    <log message="IMAP URL: ${exchangeProperty.imapUrl}, IMAP Port: ${exchangeProperty.imapPort}" />

    <!-- Dynamically resolve the IMAP endpoint -->
    <toD
        uri="imaps://${exchangeProperty.imapUrl}:${exchangeProperty.imapPort}?authenticator=#exchangeAuthenticator&amp;mail.imaps.auth.mechanisms=XOAUTH2&amp;searchTerm=#customSearchTerm" />
</route>

Answer 1

You can not use the <from uri="timer..." when you want to consume a mailbox. As the mail component supports both consumer (from) and producer (to), it behaves completely different. While the consumer will read emails from a mailbox, the producer will send emails. Therefore it complains about the missing recipient, when used in a to endpoint. There are several mechanisms to schedule the consumer (to actually get rid of the "trigger" timer). Nevertheless, this will not help you with your dynamic url, since you would need to trigger the processor first. It depends of your actual setup how you can proceed now. If you, for example have a fixed list of hosts and ports, you could set up a Map or a List, populate them with the connection data and just create multiple routes via a for-loop. As I never used the xml DSL, only Java DSL, I'm not sure, if this can be achieved with xml.

Here is an example for the java dsl:

@Component
public class MyRoute extends RouteBuilder {

    List<String> connections = List.of("myoutlook.com:993");

        @Override
        public void configure() throws Exception {
                for (String connection: connections) {
                    from("imaps://" + connection + "?authenticator=#exchangeAuthenticator&amp;mail.imaps.auth.mechanisms=XOAUTH2&amp;searchTerm=#customSearchTerm&delay=10000")
                    .routeId("mail-route-imap")
                    .log("Fetched emails from " + connection);
                }
        }
}

You could also try to use PropertyPlaceholders. Then your route could look like this:

camel-context.xml

<route id="mail-route-imap" autoStartup="true">
    <!-- Trigger the route using a timer -->
    <from uri="imaps://{{imapUrl}}:{{imapPort}}?authenticator=#exchangeAuthenticator&amp;mail.imaps.auth.mechanisms=XOAUTH2&amp;searchTerm=#customSearchTerm&amp;delay=10000" />
    <!-- Log the successful fetching of emails -->
    <log message="Fetched emails from {{imapUrl}}:{{imapPort}}" />
</route>

application.properties

imapUrl=myoutlook.com
imapPort=993

UPDATE

What you want, you can achieve with the Content Enricher, specifically with the pollEnrich endpoint. I will give the example as Java DSL, but it's also possible with xml dsl. You should be able to easily convert it to xml, but I'm not 100% sure about the syntax...

@Component
public class MyRoute extends RouteBuilder {

    @Override
    public void configure() throws Exception {
        from("timer://loadEmailParams?period=10000")
        .routeId("mail-route-imap")
        .to("sql:SELECT imapUrl, imapPort FROM connection_parameters") // get the connection parameters from the database, returns a list of Maps -> <FieldName, FieldValue>
        .split(body()) // split the records, aka process the following lines for every database record
            .pollEnrich("imaps://${body.imapUrl}:${body.imapPort}?authenticator=#exchangeAuthenticator&amp;mail.imaps.auth.mechanisms=XOAUTH2&amp;searchTerm=#customSearchTerm", new ExampleAggregationStrategy())
            .process(exchange -> {
                // do something with your emails
                // of course, you can use a real Processor here, not a lambda expression
                // the imap connection information are not available here anymore
            })
        .end();
    }
}

public class ExampleAggregationStrategy implements AggregationStrategy {

    public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
        Map<String, Object> databaseRecord = oldExchange.getIn().getBody(Map.class);
        System.out.println("Fetched emails from " + databaseRecord.get("imapUrl").toString() + ":" + databaseRecord.get("imapPort").toString());
        return newExchange;
    }
}

The ExampleAggregationStrategy prints out the current connection parameters and then returns the newExchange (which is just result of the pollEnrich endpoint), which is your emails here.

You can also check the manual https://camel.apache.org/components/4.4.x/eips/pollEnrich-eip.html and there are also examples with xml.