title: Pick specific header messages using activemq,camel selectors from queue
body: <p>How to consume specific header messages from queue. I am using camel activemq.</p>
  
  <p>routebuilder:</p>
  
  <pre><code>.....
      from("activemq:Q1").
        .setHeader("myHeader",xpath(...))
            .to("activemq:Q2")
  .....
  </code></pre>
  
  <p>and I trying to consume those messages which has the specific header in another class something like.</p>
  
  <pre><code>....
  ConsumerTemplate consumerTemplate = camelContext.createConsumerTemplate();
  Exchange exchange = consumerTemplate.receive("activemq:Q2",10000);
  
  String body = exchange.getIn().getBody(String.class);
  String customvalue = exchange.getIn().getHeader("myHeader", String.class);
  .....
  </code></pre>
  
  <p>How can I get only those messages which has myHeader=123.?</p>