How to send the contents of a file as a response back in apache camel?

Question

I have a rest api using apache camel. When I hit a post request on a route, it should get a file from S3 and send the contents of the file as a response back. I am sending json data(filename, bucketName, accesskey, secretkey, region) in order to extract the file from s3. I am able to extract the file but I don't know how to send the contents of the file back as a response. As of now, I am able to download it to my local directory.

public static class HelloRoute extends RouteBuilder {
       
        @Override
        public void configure() {
            rest("/")
                .post("file-from-s3")
                    .route()
                    .setHeader(AWS2S3Constants.KEY, constant("filename"))
                    .to("aws2-s3://bucketnameaccessKey=INSERT&secretKey=INSERT&region=INSERT&operation=getObject")
                    .to("file:/tmp/")
                    .endRest();
        }

Now instead of the .to("file:/tmp/") I want to send the contents of the file as a response back. How can I do this in apache camel?

Answer 1

Camel writes the response of the component back to the response. So, if you remove the last routing to("file:/tmp/") the response will be back with the file content.

However, I don't know about the file AWS response what it will be but if it is not the one you need, you can after writing down that to the file and create a processor that reads the file and return the content. something like:

public static class HelloRoute extends RouteBuilder {
       
        @Override
        public void configure() {

        final FileReader fileReader = new FileReader();

            rest("/")
                .post("file-from-s3")
                    .route()
                    .setHeader(AWS2S3Constants.KEY, constant("filename"))
                    .to("aws2-s3://bucketnameaccessKey=INSERT&secretKey=INSERT&region=INSERT&operation=getObject")
                    .to("file:/tmp/")
                    .process(fileReader)
                    .endRest();
        }


        public class FileReader implements Processor {


            @Override
            public void process(final Exchange exchange) {
                    //read the file from "/tmp/" and write to the body
                    //exchange.getIn().setBody(....);
            }
        }
}