service injection with parameter

[brolinuk]

I am trying to call AWS S3 bucket from our AEM. I have created an S3Manager class/service to to wrap it. which will be injected/referenced from wherever needed. This is working fine, but requires to create AmazonS3Client instance each time when I need to upload or download a file.

I am trying to initialise the amazonS3Client in the constructor instead, so I don't need to create so many instance.

private AmazonS3Client amazonS3Client;

public S3Manager(){

  String externalId = sitemapService.getAssumeRoleId();
   String roleArn = sitemapService.getRoleArn();

   amazonS3Client = getAmazonS3Client(externalId, roleArn);
}

SitemapService is another service I created to read the OSGI config (from xml or the console). The way I am doing seems not working, I am getting following exception, when initialisation try to run  sitemapService.getAssumeRoleId();

Error during instantiation of the implementation object (java.lang.NullPointerException)

I assume at the point of running, sitemapservice has not been injected yet. Is there a way, I can assure that sitemapservice injection is completed before initialise S3Manager? Or there is better way to achieve what I am looking for. Thanks

[Jörg_Hoh · Accepted solution]

When you use the standard injection (just @Reference) it has the ReferencePolicy static. That means, that this reference must be satisfied in order to acticate the component.

But I am quite sure, that your issue is different. When you implement that in the constructor, the OSGI runtime has not yet injected the references. You need to implement a service activator, see Apache Felix - Apache Felix Service Component Runtime (SCR)  for a way how to do it (note: today you are encouraged to use OSGI annotations and no longer SCR, but the activate stuff remains the same ...)

Jörg

[brolinuk]

Thanks Jörg. How would I able to make sure that the injection happens before the initialisation? I have already tried to set attribute immediate to true for the Component, but that doesn't make any difference.  Is there something I can configure the order or so ? Thanks

[Jörg_Hoh]

Make sure you understand the OSGI component livecycle. Initialization should not happen in the constructor, but rather in the activate() method (or the method annotated with @Activate).

Besides the OSGI specification (which is sometimes hard to read) I found org.osgi.service.component | osgi.enroute.site  to explain it nicely.

Jörg