Apache Camel example to get data from HTTP source does not get - apache-camel

Question

To retrieve some open data from a remote web server to process, I'm trying out Apache Camel.
The problem is that it seems that the data is never received. I have tried the jetty, ahc and cxf components but can't get it to work. For example like this:
import org.apache.camel.CamelContext;
import org.apache.camel.builder.RouteBuilder;
import org.apache.camel.impl.DefaultCamelContext;
public class CamelHttpDemo {
public static void main(final String... args) {
final CamelContext context = new DefaultCamelContext();
try {
context.addRoutes(new RouteBuilder() {
#Override
public void configure() throws Exception {
this.from("direct:start")
.to("ahc:http://camel.apache.org/")
.process(exchange -> {
System.out.println(exchange);
});
}
});
context.start();
Thread.sleep(10000);
context.stop();
} catch (final Exception e) {
e.printStackTrace();
}
}
}
No output is written so the line System.out.println(exchange); is never executed and I assume the data is not retrieved.
I'm using the most recent version of Apache Camel, 2.17.1.

Answer 1

You need some message producer in your route to emit Exchange that would trigger the http component. Your route starts with direct:start which cannot emit new Exchanges, it just sits and waits for someone to initiate the process.
The easiest way to make your route work is to replace direct:start with some producer. For instance, replacing it with this timer .from("timer://foo?fixedRate=true&period=10000") will trigger your http-request once every 10 seconds.
If you want to initiate the request manually, you need to create a ProducerTemplate and use it to send a message to direct:start. That would be:
ProducerTemplate template = context.createProducerTemplate();
template.sendMessage("direct:start", "Message body");