main.io.github.bluegroundltd.outbox.SimpleOutboxHandler.kt Maven / Gradle / Ivy

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Easily implement the transactional outbox pattern in your JVM application

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package io.github.bluegroundltd.outbox

import com.fasterxml.jackson.databind.ObjectMapper
import io.github.bluegroundltd.outbox.item.OutboxPayload
import io.github.bluegroundltd.outbox.item.OutboxType
import java.time.Clock
import java.time.Duration
import java.time.Instant

/**
 * This class purpose is to create an easy way to create an outbox handler.
 *
 * In order to achieve this, the following assumptions are made:
 * 1. Object mapper is used for serializing and deserializing outbox
 *  (Before invoking [handleWithParsedPayload] the object mapper deserializer is invoked)
 * 2. Linear retries are applied 1 minute from now (clock is used)
 *
 * Note: This is a quick solution to avoid duplicate code. It should be extracted to support
 * multiple retries policies and support configurable serialize.
 *
 */
abstract class SimpleOutboxHandler(
  private val supportedType: OutboxType,
  private val objectMapper: ObjectMapper,
  private val clock: Clock,
  private val maxRetries: Int,
  private val payloadType: Class,
) : OutboxHandler {

  companion object {
    private const val ONE_MINUTE_IN_SECONDS = 60L
    private const val TEN_DAYS = 10L
  }

  override fun getSupportedType(): OutboxType {
    return supportedType
  }

  override fun serialize(payload: OutboxPayload): String =
    objectMapper.writeValueAsString(payload)

  override fun getNextExecutionTime(currentRetries: Long): Instant = when (currentRetries) {
    0L -> Instant.now(clock)
    else -> Instant.now(clock).plusSeconds(ONE_MINUTE_IN_SECONDS)
  }

  override fun hasReachedMaxRetries(retries: Long): Boolean =
    retries >= maxRetries

  override fun handle(payload: String) {
    val payloadParsed = objectMapper.readValue(payload, payloadType)
    handleWithParsedPayload(payloadParsed)
  }

  override fun getRetentionDuration(): Duration =
    Duration.ofDays(TEN_DAYS)

  /**
   * This method is invoked after the payload is deserialized.
   * The payload is already of type [T] and can be cast to it.
   * This method should be implemented by the user.
   *
   * @param payload the payload of type [T]
   * @see [SimpleOutboxHandler]
   * @see [OutboxHandler]
   */
  abstract fun handleWithParsedPayload(payload: T)
}