ESM mapper with monads

Original_VS_Monads.kt

@Component
open class PushAccountMapper @Autowired
constructor(private val validator: Validator, private val objectMapper: ObjectMapper) : (String) -> CardProvisioningRequest {

  @Throws(ServiceException::class)
  override fun invoke(payload: String): CardProvisioningRequest {
    try {
      val request = objectMapper.readValue(payload, CardProvisioningRequest::class.java)
      val violations = validator.validate(request)

      if (violations.isNotEmpty()) {
        val stringBuilder = StringBuilder()
        violations.forEach { stringBuilder.append("${it.propertyPath} ${it.message}") }
        throw ServiceException(PushAccountError.REQUEST_VALIDATION_ERROR, "Invalid message content: $stringBuilder")
      }

      return request
    } catch (e: IOException) {
      throw ServiceException(PushAccountError.REQUEST_VALIDATION_ERROR, e.localizedMessage, e)
    }
  }
}



@Component
open class PushAccountMapperMonads @Autowired
constructor(private val validator: Validator, private val objectMapper: ObjectMapper) : (String) -> Either<Throwable, CardProvisioningRequest> {
  override fun invoke(payload: String): Either<Throwable, CardProvisioningRequest> =
      Try
          .of { objectMapper.readValue(payload, CardProvisioningRequest::class.java) }
          .toEither()
          .flatMap { validatePayload(validator, it) }

  private fun validatePayload(validator: Validator, request: CardProvisioningRequest): Either<Throwable, CardProvisioningRequest> {
    val violations = validator.validate(request)

    return if (violations.isNotEmpty()) {
      val stringBuilder = StringBuilder()
      violations.forEach { stringBuilder.append("${it.propertyPath} ${it.message}") }
      Either.left(Exception("Invalid message content: $stringBuilder"))
    } else {
      Either.right(request)
    }
  }
}

PushAccountMapperMonads.kt

package au.com.mebank.integration.dwbfaprovisioning.operation.pushAccount

import au.com.mebank.integration.dwbfaprovisioning.models.CardProvisioningRequest
import com.fasterxml.jackson.databind.ObjectMapper
import io.vavr.control.Either
import io.vavr.control.Try
import org.springframework.beans.factory.annotation.Autowired
import org.springframework.stereotype.Component
import javax.validation.Validator

@Component
open class PushAccountMapperMonads @Autowired
constructor(private val validator: Validator, private val objectMapper: ObjectMapper) : (String) -> Either<Throwable, CardProvisioningRequest> {
  override fun invoke(payload: String): Either<Throwable, CardProvisioningRequest> =
      Try
          .of { objectMapper.readValue(payload, CardProvisioningRequest::class.java) }
          .toEither()
          .flatMap { validatePayload(validator, it) }

  private fun validatePayload(validator: Validator, request: CardProvisioningRequest): Either<Throwable, CardProvisioningRequest> {
    val violations = validator.validate(request)

    return if (violations.isNotEmpty()) {
      val stringBuilder = StringBuilder()
      violations.forEach { stringBuilder.append("${it.propertyPath} ${it.message}") }
      Either.left(Exception("Invalid message content: $stringBuilder"))
    } else {
      Either.right(request)
    }
  }
}

PushAccountMapperMonadsTest.kt

package au.com.mebank.integration.dwbfaprovisioning.operation

import au.com.mebank.integration.dwbfaprovisioning.models.CardProvisioningRequest
import au.com.mebank.integration.dwbfaprovisioning.operation.pushAccount.PushAccountMapperMonads
import org.assertj.core.api.Assertions.assertThat
import org.junit.jupiter.api.BeforeEach
import org.junit.jupiter.api.Nested
import org.junit.jupiter.api.Test
import org.springframework.beans.factory.annotation.Autowired
import org.springframework.boot.test.context.SpringBootTest

@SpringBootTest
class PushAccountMapperMonadsTest {

  @Autowired
  lateinit var pushAccountMapperMonads: PushAccountMapperMonads

  lateinit var payload: String

  @BeforeEach
  fun init() {
    payload = """
        {
          "requestId": "ME00042", "cardHostId": "4444333322221111",
          "walletProvider": "applePay", "platform": "ios"
        }
      """.trimIndent()
  }

  @Test
  fun `returns an instance of CardProvisioningRequest`() {
    assertThat(pushAccountMapperMonads.invoke(payload).get())
        .isEqualTo(CardProvisioningRequest(
            "ME00042", "4444333322221111", "applePay", "ios"
        ))
  }

  @Nested
  inner class WhenThereAreErrors {
    @Nested
    inner class WhenAFieldIsBlank {
      @BeforeEach
      fun init() {
        payload = """
        {
          "requestId": "", "cardHostId": "4444333322221111",
          "walletProvider": "applePay", "platform": "ios"
        }
      """.trimIndent()
      }

      @Test
      fun `returns an error message`() {
        assertThat(pushAccountMapperMonads.invoke(payload).left.localizedMessage)
            .isEqualTo("Invalid message content: requestId must not be blank")
      }
    }

    @Nested
    inner class WhenTheFieldsDoNotBelongToTheEnumerations {
      @BeforeEach
      fun init() {
        payload = """
        {
          "requestId": "ME00042", "cardHostId": "4444333322221111",
          "walletProvider": "applePay", "platform": "nokia"
        }
      """.trimIndent()
      }

      @Test
      fun `returns an error message`() {
        assertThat(pushAccountMapperMonads.invoke(payload).left.localizedMessage)
            .isEqualTo("Invalid message content: platform must match \"android|ios\"")
      }
    }

    @Nested
    inner class WhenThereAreMissingFields {
      @BeforeEach
      fun init() {
        payload = "{\"requestId\": \"ME00042\"}"
      }

      @Test
      fun `returns an error message`() {
        assertThat(pushAccountMapperMonads.invoke(payload).left.localizedMessage)
            .contains("missing (therefore NULL) value for creator parameter cardHostId")
      }
    }
  }
}