Apache Camel 2.23.1: to(file) creates an empty file - apache-camel

Question

[JDK 8 / 11, Camel 2.23.1, Spring Boot 2.1.3]
Hi,
I'm currently learning Camel and I can't get past a strange problem.
I want to download a URL to a file.
The URL works, e.g. http://localhost/date shows "11:59:00".
The target file is created, but it's empty. Why?
#Component
public class DownloadRoute extends RouteBuilder {
#Override
public void configure() throws Exception {
String timer1 = "timer://foo?fixedRate=true&period=10000&delay=5000";
String url = "http://localhost:8888/date";
String file = "file:target/date";
from(timer1).to(url).log("${id}->${body}").to(file); // ID-Laptop-1551464093962-0-2->11:59:00, that's ok
}
}
The logger outputs the correct content, e.g.
2019-03-01 19:15:00.421 INFO 2984 --- [3 - timer://foo] route1
: ID-Laptop-1551464093962-0-2->11:59:00
but the generated file (e.g. target/date/ID-Laptop-1551464093962-0-2) is empty.
Any ideas?
Solution (thanks to Tache):
from(timer1).to(url).to(file); // without logging
OR
from(timer1).to(url).convertBodyTo(String.class).log("${id}->${body}").to(file); // with logging

Answer 1

The output of your http endpoint (http://localhost:8888/date) is probably a stream that is read using a InputStream. Such stream can be read only once.
Possible solutions:
remove your log statement
enable stream caching in your Camel context or route
convert message body to a string (.convertBodyTo(String.class) ) before logging it and sending it to a file