[Doc] Include ReaderListener example in Reader interface

[paulkmoore]

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• I searched in the issues and found nothing similar.

What issue do you find in Pulsar docs?

I think it would be useful to introduce the ReaderListener in the Reader interface introduction.

Whilst there is obviously a balance here, I think most (especially new) users would want to understand that there is a better way of processing messages than the documented while(true) loop.

What is your suggestion?

I would add something like the following:

Messages can be processed by registering an implementation of a ReaderInterface as follows:

Reader<byte[]> reader = pulsarClient.newReader()
    .topic(topic)
    .startMessageId(MessageId.latest)
    .readerListener((ReaderListener<byte[]>) (reader, msg) -> {
      // Process the message  
    })
    .create();

Any reference?

No response

Are you willing to submit a PR?

• I'm willing to submit a PR!

[tisonkun]

Hi @paulkmoore! Thanks for reporting this issue.

Since you check "I'm willing to submit a PR!", I suggest you open a pull request against the site repo: http://github.com/apache/pulsar-site

You can find the path of the page you want to edit by click the "Edit this page" button at the bottom of the page :)

For this specific issue, they are:

• https://github.com/apache/pulsar-site/blob/main/docs/concepts-clients.md for the unreleased NEXT version.
• https://github.com/apache/pulsar-site/blob/main/versioned_docs/version-2.11.x/concepts-clients.md for the latest released 2.11 version.

[momo-jun]

@paulkmoore FYI - we reorganized the client library docs in the unreleased NEXT version. This page may be a more appropriate place for you to document how to use this feature/implementation (for advanced user tasks), while Reader interface introduction focuses on the concepts.

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