Spring Boot with Kotlin and JUnit5

1. Introduction
2. Hello World
3. Project Structure
4. Data Layer
5. Data Source
6. Service Layer
7. Web Layer
8. GET Single Bank

• Tutorial 01 Introduction
  • Introduction
  • Create Project
• Tutorial 02 Hello World
  • Hello World
  • Create a REST Controller
• Tutorial 3 Project Structure
• Tutorial 4 Data Layer
• Tutorial 5 Data Source
• Tutorial 6 Service Layer
• Tutorial 7 Web Layer
• Tutorial 8 GET Single Bank

Tutorial 01 Introduction

Introduction

Video: https://youtu.be/TJcshrJOnsE?list=PL6gx4Cwl9DGDPsneZWaOFg0H2wsundyGr

• Spring Project

Create Project

• https://start.spring.io/

Spring Initializr:

• Project: Gradle
• Language: Kotlin
• Spring Boot: 2.5.0 (SNAPSHOT)
• Project Metadata
  • Group tv.codealong.tutorials.springboot
  • Artifact thenewboston
  • Name thenewboston
  • Description Spring Boot Tutorial Series for TNB
  • Package name tv.codealong.tutorials.springboot.thenewboston
  • Packaging: Jar
  • Java 11
• Dependences:
  • Spring Web

Tutorial 02 Hello World

Video: https://youtu.be/PqNgTV9enbE?list=PL6gx4Cwl9DGDPsneZWaOFg0H2wsundyGr

Hello World

touch src/main/resources/static/index.html

<h1>Hello Spring Boot</h1>

Run this project in IntelliJ IDEA, and access http://127.0.0.1:8080 in Browers.

Create a REST Controller

touch src/main/kotlin/tv/codealong/tutorials/springboot/thenewboston/HelloWorldController.kt

package tv.codealong.tutorials.springboot.thenewboston

import org.springframework.web.bind.annotation.GetMapping
import org.springframework.web.bind.annotation.RequestMapping
import org.springframework.web.bind.annotation.RestController

@RestController
@RequestMapping("api/hello")
class HelloWorldController {

    @GetMapping
    fun helloWorld(): String {
        return "Hello, this is a REST endpoint!"
    }
}

Access: http://127.0.0.1:8080/api/hello

Tutorial 3 Project Structure

Video: https://youtu.be/j5G4QZy0kZk?list=PL6gx4Cwl9DGDPsneZWaOFg0H2wsundyGr

Three files:

• build.gradle.kts
• settings.gradle.kts
• gradle/wrapper/gradle-wrapper.properties

gradle-wrapper.properties

Gradle Version in: gradle/wrapper/gradle-wrapper.properties

distributionBase=GRADLE_USER_HOME
distributionPath=wrapper/dists
distributionUrl=https\://services.gradle.org/distributions/gradle-6.8.3-bin.zip
zipStoreBase=GRADLE_USER_HOME
zipStorePath=wrapper/dists

• ./gradlew -v
• ./gradlew clean
• ./gradlew build

spring-boot-thenewboston > ./gradlew -v

------------------------------------------------------------
Gradle 6.8.3
------------------------------------------------------------

Build time:   2021-02-22 16:13:28 UTC
Revision:     9e26b4a9ebb910eaa1b8da8ff8575e514bc61c78

Kotlin:       1.4.20
Groovy:       2.5.12
Ant:          Apache Ant(TM) version 1.10.9 compiled on September 27 2020
JVM:          11.0.7 (Oracle Corporation 11.0.7+8-LTS)
OS:           Mac OS X 10.15.7 x86_64

spring-boot-thenewboston > ./gradlew clean

BUILD SUCCESSFUL in 1s
1 actionable task: 1 executed

spring-boot-thenewboston > ./gradlew build

BUILD SUCCESSFUL in 16s
8 actionable tasks: 8 executed

Tutorial 4 Data Layer

Video: https://youtu.be/1D1iL824ssk?list=PL6gx4Cwl9DGDPsneZWaOFg0H2wsundyGr

Api: https://thenewboston.com/bank-api/banks

touch src/main/kotlin/tv/codealong/tutorials/springboot/thenewboston/model/Bank.kt

package tv.codealong.tutorials.springboot.thenewboston.model

data class Bank(
    val accountNumber: String,
    val trust: Double,
    val transactionFee: Int
)

Tutorial 5 Data Source

Video: https://youtu.be/VVrKvpqAmw8?list=PL6gx4Cwl9DGDPsneZWaOFg0H2wsundyGr

touch src/main/kotlin/tv/codealong/tutorials/springboot/thenewboston/datasource/BankDataSource.kt

package tv.codealong.tutorials.springboot.thenewboston.datasource

import tv.codealong.tutorials.springboot.thenewboston.model.Bank

interface BankDataSource {
    fun retrieveBanks(): Collection<Bank>
}

touch src/main/kotlin/tv/codealong/tutorials/springboot/thenewboston/datasource/mock/MockBankDataSource.kt

package tv.codealong.tutorials.springboot.thenewboston.datasource.mock

import org.springframework.stereotype.Repository
import tv.codealong.tutorials.springboot.thenewboston.datasource.BankDataSource
import tv.codealong.tutorials.springboot.thenewboston.model.Bank

@Repository
class MockBankDataSource : BankDataSource {

    val banks = listOf(
        Bank("aaa", 2.0, 1),
        Bank("bbb", 3.0, 2),
        Bank("ccc", 4.0, 3)
    )

    override fun retrieveBanks(): Collection<Bank> = banks
}

touch src/test/kotlin/tv/codealong/tutorials/springboot/thenewboston/datasource/mock/MockBankDataSourceTest.kt

package tv.codealong.tutorials.springboot.thenewboston.datasource.mock

import org.assertj.core.api.Assertions.assertThat
import org.junit.jupiter.api.Test

internal class MockBankDataSourceTest {
    private val mockDataSource: MockBankDataSource = MockBankDataSource()

    @Test
    fun `should provide a collection of banks`() {
        // when
        val banks = mockDataSource.retrieveBanks()

        // then
        assertThat(banks).isNotEmpty
        assertThat(banks.size).isGreaterThanOrEqualTo(3)
    }

    @Test
    fun `should provide some mock data`() {
        // when
        val banks = mockDataSource.retrieveBanks()

        // then
        assertThat(banks).allSatisfy { it.accountNumber.isNotBlank() }
        assertThat(banks).allMatch { it.accountNumber.isNotBlank() }
        assertThat(banks).anyMatch { it.trust != 0.0 }
        assertThat(banks).anyMatch { it.transactionFee != 0 }
    }
}

Tutorial 6 Service Layer

Video: https://youtu.be/Icnb3zvya-w?list=PL6gx4Cwl9DGDPsneZWaOFg0H2wsundyGr

• build.gradle.kts

Add testImplementation("io.mockk:mockk:1.10.4"):

dependencies {
    # ...
    testImplementation("io.mockk:mockk:1.10.4")
}

• src/main/kotlin/tv/codealong/tutorials/springboot/thenewboston/service/BankService.kt

package tv.codealong.tutorials.springboot.thenewboston.service

import io.mockk.mockk
import io.mockk.verify
import org.junit.jupiter.api.Test
import tv.codealong.tutorials.springboot.thenewboston.datasource.BankDataSource

internal class BankServiceTest {
    private val dataSource: BankDataSource = mockk(relaxed = true)
    private val bankService: BankService = BankService(dataSource)

    @Test
    fun `should call its data source to retrieve banks`() {
        // given
        // every { dataSource.retrieveBanks() } returns emptyList()

        // when
        val banks = bankService.getBanks()

        // then
        verify(exactly = 1) { dataSource.retrieveBanks() }
    }
}

• src/test/kotlin/tv/codealong/tutorials/springboot/thenewboston/service/BankServiceTest.kt

package tv.codealong.tutorials.springboot.thenewboston.datasource.mock

import org.assertj.core.api.Assertions.assertThat
import org.junit.jupiter.api.Test

internal class MockBankDataSourceTest {
    private val mockDataSource: MockBankDataSource = MockBankDataSource()

    @Test
    fun `should provide a collection of banks`() {
        // when
        val banks = mockDataSource.retrieveBanks()

        // then
        assertThat(banks).isNotEmpty
        assertThat(banks.size).isGreaterThanOrEqualTo(3)
    }

    @Test
    fun `should provide some mock data`() {
        // when
        val banks = mockDataSource.retrieveBanks()

        // then
        assertThat(banks).allSatisfy { it.accountNumber.isNotBlank() }
        assertThat(banks).allMatch { it.accountNumber.isNotBlank() }
        assertThat(banks).anyMatch { it.trust != 0.0 }
        assertThat(banks).anyMatch { it.transactionFee != 0 }
    }
}

Tutorial 7 Web Layer

Video: https://youtu.be/2e72RHO8ORk?list=PL6gx4Cwl9DGDPsneZWaOFg0H2wsundyGr

• src/main/kotlin/tv/codealong/tutorials/springboot/thenewboston/controller/BankController.kt

  package tv.codealong.tutorials.springboot.thenewboston.controller
  
  import org.springframework.web.bind.annotation.GetMapping
  import org.springframework.web.bind.annotation.RequestMapping
  import org.springframework.web.bind.annotation.RestController
  import tv.codealong.tutorials.springboot.thenewboston.model.Bank
  import tv.codealong.tutorials.springboot.thenewboston.service.BankService
  
  @RestController
  @RequestMapping("/api/banks")
  class BankController(private val service: BankService) {
      @GetMapping
      fun getBanks(): Collection<Bank> = service.getBanks()
  }

• src/test/kotlin/tv/codealong/tutorials/springboot/thenewboston/controller/BankControllerTest.kt

  package tv.codealong.tutorials.springboot.thenewboston.controller
  
  import org.junit.jupiter.api.Test
  import org.springframework.beans.factory.annotation.Autowired
  import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc
  import org.springframework.boot.test.context.SpringBootTest
  import org.springframework.http.MediaType
  import org.springframework.test.web.servlet.MockMvc
  import org.springframework.test.web.servlet.get
  
  @SpringBootTest
  @AutoConfigureMockMvc
  internal class BankControllerTest {
  
      @Autowired
      lateinit var mockMvc: MockMvc
  
      @Test
      fun `should return all banks`() {
          mockMvc.get("/api/banks")
              .andDo { print() }
              .andExpect {
                  status { isOk() }
                  content { contentType(MediaType.APPLICATION_JSON) }
                  jsonPath("$[0].accountNumber") { value("aaa") }
              }
      }
  }

Access to http://127.0.0.1:8080/api/banks

[
{
"accountNumber": "aaa",
"trust": 2,
"transactionFee": 1
},
{
"accountNumber": "bbb",
"trust": 3,
"transactionFee": 2
},
{
"accountNumber": "ccc",
"trust": 4,
"transactionFee": 3
}
]

Tutorial 8 GET Single Bank

Video: https://youtu.be/jiv37i503v4?list=PL6gx4Cwl9DGDPsneZWaOFg0H2wsundyGr