load producer / consumer config from properties file

[gAmUssA]

ref. https://github.com/confluentinc/examples/blob/5.5.1-post/clients/cloud/kotlin/src/main/kotlin/io/confluent/examples/clients/cloud/util/Utils.kt

[fhussonnois]

Hi @gAmUssA, thank you for the issue. Since I was working on refactoring the configuration classes KafkaConsumerConfigs, KafkaProducerConfigs (which now implement MutableMap), I've added Kotlin extensions to easily load config from properties file.

Some examples showing how to load config file :

   // Example 1 -> KafkaConsumerConfigs can be directly used to create a new KafkaConsumer
    KafkaConsumer<String, String>(KafkaConsumerConfigs()
        .load("/tmp/config.properties")
        .keyDeserializer(StringDeserializer::class.java.name)
        .valueDeserializer(StringDeserializer::class.java.name)
    ).use {
        // do something useful
    }

    // Example 2 -> using convenient function
    // i.e : one of : loadClientConfigs, loadConsumerConfig, loadProducerConfigs
    val configs: KafkaProducerConfigs = loadProducerConfigs("/tmp/config.properties")

    // Example 3 -> also work with KafkaClients DSL
    kafka(loadClientConfigs("/tmp/config.properties")) {
        client {
            clientId("demo-client")
        }
    }