Скачать или смотреть Spring Integration Java DSL with Kafka: A Step-by-Step Guide to Publish Messages

Discover how to correctly configure Spring Integration Java DSL with Kafka to seamlessly publish messages to your Kafka topic from a database.
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This video is based on the question https://stackoverflow.com/q/78119343/ asked by the user 'Sha' ( https://stackoverflow.com/u/23543923/ ) and on the answer https://stackoverflow.com/a/78122808/ provided by the user 'Artem Bilan' ( https://stackoverflow.com/u/2756547/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Introduction

If you are working with Spring Integration and Kafka, you might encounter challenges while transitioning data from your database (DB) to a Kafka topic. One common issue is successfully publishing messages to a Kafka topic. In this guide, we'll explore a practical example of a Java DSL configuration using Spring Integration and Kafka, and we will address a common pitfall you might face when implementing this solution.

Problem Statement

You're attempting to read rows from your database and send them as messages to a Kafka topic. While your code compiles and successfully fetches records from the DB, you notice that the messages aren't appearing in the designated Kafka topic. Let's dive into the solution and understand how to fix this issue.

Solution Overview

To ensure that messages are correctly published to your Kafka topic, you need to implement the handle() method correctly when configuring your outbound channel adapter with Kafka.

Configuration Correction

The main issue in your original code lies in the use of the handle() method. In your existing configuration, you were creating a new MessageHandler within a lambda expression, which is not the correct approach. Instead, you should provide a MessageHandler that remains consistent throughout the application run. Here's how to do that:

Original Code Setup

Here's a snippet of the problematic code that needs correction:

[[See Video to Reveal this Text or Code Snippet]]

Correcting the Configuration

Instead of creating a new MessageHandler, configure the outbound adapter like this:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of Changes

Consistent MessageHandler Creation: By restructuring your handle() definition, the MessageHandler is created once during the configuration phase, allowing Spring to call its handleMessage() method correctly for each message at runtime.

Lambda Functions: In this corrected configuration, lambdas are used to dynamically provide the topic, message key, and partition ID during message handling, thus maintaining flexibility within the stable architecture of your application.

Conclusion

In summary, when integrating Spring with Kafka using Java DSL, ensure that you properly configure your outbound channel adapters. Pay attention to how you set up your handlers; creating handlers dynamically within the handle() method can lead to issues like messages failing to publish. By following the outlined corrections, you should be able to see your messages being published to the Kafka topic successfully.

If you encounter further issues, don't hesitate to reach out for more guidance or consult the extensive Spring documentation. Happy coding!