Camel bean binding: set parameter from variable - apache-camel

Question

Given a bean method that takes a String parameter:
public void emptyDirectory(String directory) {
// code to empty give directory if it exists
}
how do i pass this parameter? The method is called here:
String to = configuration.getTo();
from(configuration.getFrom())
.to("bean:splitFileByProductType?method=emptyDirectory(to)")
....
This doesn't work as 'to' evaluates to "to", and not the value of configuration.getTo().
The documentation does not mention a case like this, so i don't know if what i'm trying to do is even possible, for example in the Simple language.
I know the value becomes accessible if i add it to the exchange header or if i hardcode it.

Answer 1

You can pass a value as method argument with ${body}, ${body.NAME}, ${property.NAME} and ${header.NAME}.
Examples http://camel.apache.org/bean-binding.html
So first of all you have to put your variable in Camel exchange.

Answer 2

To pass information from the Camel Exchange to a bean method you must not add or change anything in the route.
If you have this route (from your question). Notice that if the bean has only one method you can omit the method name.
from(whatever)
.to("bean:splitFileByProductType?methodName=emptyDirectory")
Or alternative
from(whatever)
.bean(splitFileByProductType, "emptyDirectory")
You can annotate your bean method to get the needed Exchange information automagically:
public void emptyDirectory(
#Header("directory") String directory,
#Body String body
... [other stuff to be injected] ) {
// your method impl
}
See the Camel docs for more information about this feature.

Answer 3

You could assign the parameter to an exchange header or property and then use simple language to pass it the bean method
String to = configuration.getTo();
from(configuration.getFrom())
.setHeader("foo", constant(to))
.to("bean:splitFileByProductType?method=emptyDirectory(${header.foo})")
...

Answer 4

From documentation:
The only things that can be passed to a bean are Simple tokens, a String value, a numeric value, a boolean or null.
The variable from the example cannot be expressed using Simple. What can be expressed are various properties of the exchange, most notably the exchange headers, and also some random things like literally random numbers, the current date and so on. Check the documentation for more info.
I decided to treat the whole thing as a code smell, and moved the method to a utility class which i call prior to initializing the route.