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Add link builder DSL to write idiomatic Kotlin code
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‎pom.xml

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<dependencies>
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<!-- Kotlin extension -->
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<dependency>
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<groupId>org.jetbrains.kotlin</groupId>
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<artifactId>kotlin-stdlib</artifactId>
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<version>1.2.71</version>
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<optional>true</optional>
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</dependency>
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<dependency>
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<groupId>org.jetbrains.kotlin</groupId>
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<artifactId>kotlin-reflect</artifactId>
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<version>1.2.71</version>
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<optional>true</optional>
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</dependency>
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<dependency>
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<groupId>org.jetbrains.kotlin</groupId>
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<artifactId>kotlin-test</artifactId>
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<version>1.2.71</version>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>org.springframework</groupId>
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<artifactId>spring-aop</artifactId>
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<useSystemClassLoader>false</useSystemClassLoader>
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</configuration>
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</plugin>
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<plugin>
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<groupId>org.jetbrains.kotlin</groupId>
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<artifactId>kotlin-maven-plugin</artifactId>
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<version>1.2.71</version>
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<executions>
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<execution>
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<id>compile</id>
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<phase>process-sources</phase>
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<goals>
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<goal>compile</goal>
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</goals>
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</execution>
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</executions>
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</plugin>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-deploy-plugin</artifactId>
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<version>2.8.2</version>
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</plugin>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>

‎src/main/kotlin/org/springframework/hateoas/LinkBuilderDsl.kt

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/*
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* Copyright 2002-2019 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.hateoas
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import org.springframework.hateoas.mvc.ControllerLinkBuilder
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import org.springframework.hateoas.mvc.ControllerLinkBuilder.afford
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import org.springframework.hateoas.mvc.ControllerLinkBuilder.linkTo
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import org.springframework.hateoas.mvc.ControllerLinkBuilder.methodOn
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import kotlin.reflect.KClass
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/**
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* Creates the [Link] with the given [rel].
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*
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* @author Roland Kulcsár
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*/
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infix fun ControllerLinkBuilder.withRel(rel: String): Link = withRel(rel)
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/**
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* Create new [Link] with additional [Affordance]s.
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*
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* @author Roland Kulcsár
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*/
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inline infix fun Link.andAffordances(setup: AffordancesBuilderDsl.() -> Unit): Link {
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val builder = AffordancesBuilderDsl()
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builder.setup()
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return andAffordances(builder.affordances)
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}
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/**
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* Creates a [ControllerLinkBuilder] pointing to [func] method.
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*
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* @author Roland Kulcsár
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*/
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inline fun <reified C> linkTo(func: C.() -> Unit): ControllerLinkBuilder = linkTo(methodOn(C::class.java).apply(func))
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/**
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* Extract a [Link] from the [ControllerLinkBuilder] and look up the related [Affordance]. Should
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* only be one.
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*
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* @author Roland Kulcsár
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*/
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inline fun <reified C> afford(func: C.() -> Unit): Affordance = afford(methodOn(C::class.java).apply(func))
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/**
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* Adds the [links] to the [R] resource.
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*
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* @author Roland Kulcsár
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*/
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fun <C, R : ResourceSupport> R.add(controller: Class<C>, links: LinkBuilderDsl<C, R>.(R) -> Unit): R {
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val builder = LinkBuilderDsl(controller, this)
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builder.links(this)
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return this
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}
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/**
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* Adds the [links] to the [R] resource.
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*
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* @author Roland Kulcsár
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*/
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fun <C : Any, R : ResourceSupport> R.add(controller: KClass<C>, links: LinkBuilderDsl<C, R>.(R) -> Unit): R {
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return add(controller.java, links)
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}
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/**
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* Provides a link builder Kotlin DSL in order to be able to write idiomatic Kotlin code.
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*
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* @author Roland Kulcsár
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*/
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open class LinkBuilderDsl<C, R : ResourceSupport>(val controller: Class<C>, val resource: R) {
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/**
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* Creates a [ControllerLinkBuilder] pointing to [func] method.
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*/
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fun <R> linkTo(func: C.() -> R): ControllerLinkBuilder = linkTo(methodOn(controller).run(func))
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/**
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* Adds link with the given [rel] to [resource].
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*/
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infix fun ControllerLinkBuilder.withRel(rel: String): Link {
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val link = withRel(rel)
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resource.add(link)
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return link
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}
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}
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/**
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* Provides an affordances builder Kotlin DSL in order to be able to write idiomatic Kotlin code.
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*
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* @author Roland Kulcsár
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*/
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open class AffordancesBuilderDsl(val affordances: MutableList<Affordance> = mutableListOf()) {
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inline fun <reified C> afford(func: C.() -> Any) {
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val affordance = afford(methodOn(C::class.java).func())
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affordances.add(affordance)
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}
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}

‎src/test/kotlin/org/springframework/hateoas/LinkBuilderDslUnitTest.kt

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/*
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* Copyright 2002-2019 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.hateoas
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import org.assertj.core.api.Assertions.assertThat
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import org.junit.Test
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import org.springframework.http.HttpMethod
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import org.springframework.http.ResponseEntity
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import org.springframework.web.bind.annotation.DeleteMapping
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import org.springframework.web.bind.annotation.GetMapping
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import org.springframework.web.bind.annotation.PathVariable
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import org.springframework.web.bind.annotation.PutMapping
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import org.springframework.web.bind.annotation.RequestBody
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import org.springframework.web.bind.annotation.RequestMapping
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/**
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* Unit tests for [LinkBuilderDsl].
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*
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* @author Roland Kulcsár
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*/
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class LinkBuilderDslUnitTest : TestUtils() {
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private val REL_PRODUCTS = "products"
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@Test
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fun `creates link to controller method`() {
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val self = linkTo<CustomerController> { findById("15") } withRel Link.REL_SELF
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assertPointsToMockServer(self)
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assertThat(self.rel).isEqualTo(Link.REL_SELF)
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assertThat(self.href).endsWith("/customers/15")
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}
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@Test
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fun `creates affordance to controller method`() {
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val delete = afford<CustomerController> { delete("15") }
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assertThat(delete.httpMethod).isEqualTo(HttpMethod.DELETE)
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assertThat(delete.name).isEqualTo("delete")
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}
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@Test
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fun `creates link to controller method with affordances`() {
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val id = "15"
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val self = linkTo<CustomerController> { findById(id) } withRel Link.REL_SELF
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val selfWithAffordances = self andAffordances {
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afford<CustomerController> { update(id, CustomerDto("John Doe")) }
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afford<CustomerController> { delete(id) }
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}
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assertThat(selfWithAffordances.affordances).hasSize(3)
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assertThat(selfWithAffordances.hashCode()).isNotEqualTo(self.hashCode())
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assertThat(selfWithAffordances).isNotEqualTo(self)
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}
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@Test
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fun `adds links to wrapped domain object`() {
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val customer = Resource(Customer("15", "John Doe"))
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customer.add(CustomerController::class) {
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linkTo { findById(it.content.id) } withRel Link.REL_SELF
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linkTo { findProductsById(it.content.id) } withRel REL_PRODUCTS
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}
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customer.links.forEach { assertPointsToMockServer(it) }
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assertThat(customer.hasLink(Link.REL_SELF)).isTrue()
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assertThat(customer.hasLink(REL_PRODUCTS)).isTrue()
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}
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@Test
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fun `adds links to resource`() {
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val customer = CustomerResource("15", "John Doe")
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customer.add(CustomerController::class) {
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linkTo { findById(it.id) } withRel Link.REL_SELF
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linkTo { findProductsById(it.id) } withRel REL_PRODUCTS
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}
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customer.links.forEach { assertPointsToMockServer(it) }
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assertThat(customer.hasLink(Link.REL_SELF)).isTrue()
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assertThat(customer.hasLink(REL_PRODUCTS)).isTrue()
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}
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data class Customer(val id: String, val name: String)
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data class CustomerDto(val name: String)
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open class CustomerResource(val id: String, val name: String) : ResourceSupport()
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open class ProductResource(val id: String) : ResourceSupport()
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@RequestMapping("/customers")
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interface CustomerController {
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@GetMapping("/{id}")
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fun findById(@PathVariable id: String): ResponseEntity<CustomerResource>
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@GetMapping("/{id}/products")
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fun findProductsById(@PathVariable id: String): PagedResources<ProductResource>
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@PutMapping("/{id}")
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fun update(@PathVariable id: String, @RequestBody customer: CustomerDto): ResponseEntity<CustomerResource>
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@DeleteMapping("/{id}")
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fun delete(@PathVariable id: String): ResponseEntity<Unit>
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}
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}

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