Tuesday, June 27, 2017

Spring Webflux - Kotlin DSL

Spring Webflux has introduced a feature for defining functional application endpoints using a very intuitive Kotlin based DSL

This post will be to simply show a contrasting api defined using a Java based fluent api and a Kotlin based DSL


A functional way to define a CRUD based Spring Webflux endpoint in Java would look like this:


RouterFunction<?> apis() {
    return nest(path("/hotels"), nest(accept(MediaType.APPLICATION_JSON),
            route(
                    GET("/"), messageHandler::getMessages)
                    .andRoute(POST("/"), messageHandler::addMessage)
                    .andRoute(GET("/{id}"), messageHandler::getMessage)
                    .andRoute(PUT("/{id}"), messageHandler::updateMessage)
                    .andRoute(DELETE("/{id}"), messageHandler::deleteMessage)
    ));
}

The details of the endpoint is very clear and is defined in a fluent manner with just a few keywords - route, nest and the HTTP verbs.

These endpoints can be expressed using a Kotlin based DSL(and some clever use of Kotlin extension functions) the following way:

@Bean
fun apis() = router {
    (accept(APPLICATION_JSON) and "/messages").nest {
        GET("/", messageHandler::getMessages)
        POST("/", messageHandler::addMessage)
        GET("/{id}", messageHandler::getMessage)
        PUT("/{id}", messageHandler::updateMessage)
        DELETE("/{id}", messageHandler::deleteMessage)
    }
}

I feels that this reads a little better than the Java based DSL. If the API is more complicated, as demonstrated in the excellent samples by S├ębastien Deleuze with multiple levels of nesting, the Kotlin based DSL really starts to shine.


In the next post, I will delve into how this support has been implemented.

This sample is available in my github repo here

Sunday, June 11, 2017

Spring Boot Web Slice test - Sample

Spring Boot introduced test slicing a while back and it has taken me some time to get my head around it and explore some of its nuances.

Background


The main reason to use this feature is to reduce the boilerplate. Consider a controller that looks like this, just for variety written using Kotlin.

@RestController
@RequestMapping("/users")
class UserController(
        private val userRepository: UserRepository,
        private val userResourceAssembler: UserResourceAssembler) {

    @GetMapping
    fun getUsers(pageable: Pageable, 
                 pagedResourcesAssembler: PagedResourcesAssembler<User>): PagedResources<Resource<User>> {
        val users = userRepository.findAll(pageable)
        return pagedResourcesAssembler.toResource(users, this.userResourceAssembler)
    }

    @GetMapping("/{id}")
    fun getUser(id: Long): Resource<User> {
        return Resource(userRepository.findOne(id))
    }
}


A traditional Spring Mock MVC test to test this controller would be along these lines:

@RunWith(SpringRunner::class)
@WebAppConfiguration
@ContextConfiguration
class UserControllerTests {

    lateinit var mockMvc: MockMvc

    @Autowired
    private val wac: WebApplicationContext? = null

    @Before
    fun setup() {
        this.mockMvc = MockMvcBuilders.webAppContextSetup(this.wac).build()
    }

    @Test
    fun testGetUsers() {
        this.mockMvc.perform(get("/users")
                .accept(MediaType.APPLICATION_JSON))
                .andDo(print())
                .andExpect(status().isOk)
    }

    @EnableSpringDataWebSupport
    @EnableWebMvc
    @Configuration
    class SpringConfig {

        @Bean
        fun userController(): UserController {
            return UserController(userRepository(), UserResourceAssembler())
        }

        @Bean
        fun userRepository(): UserRepository {
            val userRepository = Mockito.mock(UserRepository::class.java)
            given(userRepository.findAll(Matchers.any(Pageable::class.java)))
                    .willAnswer({ invocation ->
                        val pageable = invocation.arguments[0] as Pageable
                        PageImpl(
                                listOf(
                                        User(id = 1, fullName = "one", password = "one", email = "one@one.com"),
                                        User(id = 2, fullName = "two", password = "two", email = "two@two.com"))
                                , pageable, 10)
                    })
            return userRepository
        }
    }
}

There is a lot of ceremony involved in setting up such a test - a web application context which understands a web environment is pulled in, a configuration which sets up the Spring MVC environment needs to be created and MockMvc which is handle to the testing framework needs to be set-up before each test.


Web Slice Test

A web slice test when compared to the previous test is far simpler and focuses on testing the controller and hides a lot of the boilerplate code:

@RunWith(SpringRunner::class)
@WebMvcTest(UserController::class)
class UserControllerSliceTests {

    @Autowired
    lateinit var mockMvc: MockMvc

    @MockBean
    lateinit var userRepository: UserRepository

    @SpyBean
    lateinit var userResourceAssembler: UserResourceAssembler

    @Test
    fun testGetUsers() {

        this.mockMvc.perform(get("/users").param("page", "0").param("size", "1")
                .accept(MediaType.APPLICATION_JSON))
                .andDo(print())
                .andExpect(status().isOk)
    }

    @Before
    fun setUp(): Unit {
        given(userRepository.findAll(Matchers.any(Pageable::class.java)))
                .willAnswer({ invocation ->
                    val pageable = invocation.arguments[0] as Pageable
                    PageImpl(
                            listOf(
                                    User(id = 1, fullName = "one", password = "one", email = "one@one.com"),
                                    User(id = 2, fullName = "two", password = "two", email = "two@two.com"))
                            , pageable, 10)
                })
    }
}

It works by creating a Spring Application context but filtering out anything that is not relevant to the web layer and loading up only the controller which has been passed into the @WebTest annotation. Any dependency that the controller requires can be injected in as a mock.


Coming to some of the nuances, say if I wanted to inject one of the fields myself the way to do it is have the test use a custom Spring Configuration, for a test this is done by using a inner static class annotated with @TestConfiguration the following way:

@RunWith(SpringRunner::class)
@WebMvcTest(UserController::class)
class UserControllerSliceTests {

    @Autowired
    lateinit var mockMvc: MockMvc

    @Autowired
    lateinit var userRepository: UserRepository

    @Autowired
    lateinit var userResourceAssembler: UserResourceAssembler

    @Test
    fun testGetUsers() {

        this.mockMvc.perform(get("/users").param("page", "0").param("size", "1")
                .accept(MediaType.APPLICATION_JSON))
                .andDo(print())
                .andExpect(status().isOk)
    }

    @Before
    fun setUp(): Unit {
        given(userRepository.findAll(Matchers.any(Pageable::class.java)))
                .willAnswer({ invocation ->
                    val pageable = invocation.arguments[0] as Pageable
                    PageImpl(
                            listOf(
                                    User(id = 1, fullName = "one", password = "one", email = "one@one.com"),
                                    User(id = 2, fullName = "two", password = "two", email = "two@two.com"))
                            , pageable, 10)
                })
    }

    @TestConfiguration
    class SpringConfig {

        @Bean
        fun userResourceAssembler(): UserResourceAssembler {
            return UserResourceAssembler()
        }

        @Bean
        fun userRepository(): UserRepository {
            return mock(UserRepository::class.java)
        }
    }

}


The beans from the "TestConfiguration" adds on to the configuration which the Slice tests depend on and don't completely replace it.

On the other hand, if I wanted to override the loading of the main "@SpringBootApplication" annotated class then I can pass in a Spring Configuration class explicitly, but the catch is that I have to now take care of all of loading up the relevant Spring Boot features myself (enabling auto-configuration, appropriate scanning etc), so a way around it to explicitly annotate the configuration as a Spring Boot Application the following way:

@RunWith(SpringRunner::class)
@WebMvcTest(UserController::class)
class UserControllerExplicitConfigTests {

    @Autowired
    lateinit var mockMvc: MockMvc

    @Autowired
    lateinit var userRepository: UserRepository

    @Test
    fun testGetUsers() {

        this.mockMvc.perform(get("/users").param("page", "0").param("size", "1")
                .accept(MediaType.APPLICATION_JSON))
                .andDo(print())
                .andExpect(status().isOk)
    }

    @Before
    fun setUp(): Unit {
        given(userRepository.findAll(Matchers.any(Pageable::class.java)))
                .willAnswer({ invocation ->
                    val pageable = invocation.arguments[0] as Pageable
                    PageImpl(
                            listOf(
                                    User(id = 1, fullName = "one", password = "one", email = "one@one.com"),
                                    User(id = 2, fullName = "two", password = "two", email = "two@two.com"))
                            , pageable, 10)
                })
    }

    @SpringBootApplication(scanBasePackageClasses = arrayOf(UserController::class))
    @EnableSpringDataWebSupport
    class SpringConfig {

        @Bean
        fun userResourceAssembler(): UserResourceAssembler {
            return UserResourceAssembler()
        }

        @Bean
        fun userRepository(): UserRepository {
            return mock(UserRepository::class.java)
        }
    }

}


The catch though is that now other tests may end up finding this inner configuration which is far from ideal!, so my learning has been to depend on bare minimum slice testing, and if needed extend it using @TestConfiguration.


I have a little more detailed code sample available at my github repo which has working examples to play with.