#1213 - Add support for Kotlin co-routines.

The ReactiveRepresentationModelAssembler and SimpleRepresentationModelAssembler both accept Flux inputs for entities. This change adds support for Kotlin co-routines to the same inputs.

Related pull request: #1258.

pom.xml

@@ -85,6 +85,8 @@
 		<spring.version>5.2.5.RELEASE</spring.version>
 		<spring-plugin.version>2.0.0.RELEASE</spring-plugin.version>
 		<kotlin.version>1.3.71</kotlin.version>
+		<kotlinx-coroutines.version>1.3.5</kotlinx-coroutines.version>
+		<mockk.version>1.9.3</mockk.version>
 	</properties>
 
 	<profiles>
@@ -704,6 +706,20 @@
 				<type>pom</type>
 				<scope>import</scope>
 			</dependency>
+			<dependency>
+				<groupId>org.jetbrains.kotlin</groupId>
+				<artifactId>kotlin-bom</artifactId>
+				<version>${kotlin.version}</version>
+				<type>pom</type>
+				<scope>import</scope>
+			</dependency>
+			<dependency>
+				<groupId>org.jetbrains.kotlinx</groupId>
+				<artifactId>kotlinx-coroutines-bom</artifactId>
+				<version>${kotlinx-coroutines.version}</version>
+				<type>pom</type>
+				<scope>import</scope>
+			</dependency>
 		</dependencies>
 	</dependencyManagement>
 
@@ -713,13 +729,16 @@
 		<dependency>
 			<groupId>org.jetbrains.kotlin</groupId>
 			<artifactId>kotlin-stdlib</artifactId>
-			<version>${kotlin.version}</version>
 			<optional>true</optional>
 		</dependency>
 		<dependency>
 			<groupId>org.jetbrains.kotlin</groupId>
 			<artifactId>kotlin-reflect</artifactId>
-			<version>${kotlin.version}</version>
+			<optional>true</optional>
+		</dependency>
+		<dependency>
+			<groupId>org.jetbrains.kotlinx</groupId>
+			<artifactId>kotlinx-coroutines-reactor</artifactId>
 			<optional>true</optional>
 		</dependency>
 		<dependency>
@@ -728,6 +747,12 @@
 			<version>${kotlin.version}</version>
 			<scope>test</scope>
 		</dependency>
+		<dependency>
+			<groupId>io.mockk</groupId>
+			<artifactId>mockk</artifactId>
+			<version>${mockk.version}</version>
+			<scope>test</scope>
+		</dependency>
 
 		<dependency>
 			<groupId>org.springframework</groupId>

src/main/kotlin/org/springframework/hateoas/server/reactive/ReactiveRepresentationModelAssemblerBuildDsl.kt

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.hateoas.server.reactive
+
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.reactive.awaitFirst
+import kotlinx.coroutines.reactor.asFlux
+import org.springframework.hateoas.CollectionModel
+import org.springframework.hateoas.RepresentationModel
+import org.springframework.web.server.ServerWebExchange
+
+/**
+ * Add support for Kotlin co-routines.
+ *
+ * @author Juergen Zimmerman
+ * @author Greg Turnquist
+ * @since 1.1
+ */
+suspend fun <T : Any, D : RepresentationModel<D>> ReactiveRepresentationModelAssembler<T, D>.toCollectionModel(
+    entities: Flow<T>,
+    exchange: ServerWebExchange): CollectionModel<D> = toCollectionModel(entities.asFlux(), exchange).awaitFirst()

src/main/kotlin/org/springframework/hateoas/server/reactive/SimpleReactiveRepresentationModelAssemblerBuildDsl.kt

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.hateoas.server.reactive
+
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.reactive.awaitFirst
+import kotlinx.coroutines.reactor.asFlux
+import org.springframework.hateoas.CollectionModel
+import org.springframework.hateoas.EntityModel
+import org.springframework.web.server.ServerWebExchange
+
+/**
+ * Add support for Kotlin co-routines.
+ *
+ * @author Juergen Zimmerman
+ * @author Greg Turnquist
+ * @since 1.1
+ */
+suspend fun <T : Any> SimpleReactiveRepresentationModelAssembler<T>.toCollectionModel(
+    entities: Flow<T>,
+    exchange: ServerWebExchange): CollectionModel<EntityModel<T>> = toCollectionModel(entities.asFlux(), exchange).awaitFirst()

src/test/kotlin/org/springframework/hateoas/server/reactive/ReactiveRepresentationModelAssemblerBuilderDslUnitTest.kt

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2019-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.hateoas.server.reactive
+
+import io.mockk.mockk
+import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.runBlocking
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+import org.springframework.hateoas.EntityModel
+import org.springframework.hateoas.Link
+import org.springframework.hateoas.LinkRelation
+import org.springframework.hateoas.TestUtils
+import org.springframework.web.server.ServerWebExchange
+import reactor.core.publisher.Mono
+
+/**
+ * @author Greg Turnquist
+ * @since 1.1
+ */
+class ReactiveRepresentationModelAssemblerBuilderDslUnitTest : TestUtils() {
+
+    private val EMPLOYEES_RELATION = LinkRelation.of("employees")
+
+    private val employees = flow {
+        emit(Employee("Frodo"))
+        emit(Employee("Bilbo"))
+    }
+
+    @Test // #1213
+    fun `Kotlin Flows should render as CollectionModels`() {
+
+        val testResourceAssembler = TestResourceAssembler()
+        val exchange = mockk<ServerWebExchange>()
+
+        runBlocking {
+            val collectionModel = testResourceAssembler.toCollectionModel(employees, exchange)
+
+            assertThat(collectionModel.content.flatMap { entityModel -> entityModel.links })
+                .containsExactlyInAnyOrder(Link.of("/employees", EMPLOYEES_RELATION), Link.of("/employees", EMPLOYEES_RELATION))
+        }
+    }
+
+    class TestResourceAssembler : ReactiveRepresentationModelAssembler<Employee, EntityModel<Employee>> {
+        override fun toModel(entity: Employee, exchange: ServerWebExchange): Mono<EntityModel<Employee>> {
+            return Mono.just(EntityModel.of(entity, Link.of("/employees", LinkRelation.of("employees"))))
+        }
+    }
+
+    data class Employee(val name: String)
+
+}

src/test/kotlin/org/springframework/hateoas/server/reactive/SimpleReactiveRepresentationModelAssemblerBuilderDslUnitTest.kt

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2019-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.hateoas.server.reactive
+
+import io.mockk.mockk
+import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.runBlocking
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+import org.springframework.hateoas.*
+import org.springframework.web.server.ServerWebExchange
+
+/**
+ * @author Greg Turnquist
+ * @since 1.1
+ */
+class SimpleReactiveRexpresentationModelAssemblerBuilderDslUnitTest : TestUtils() {
+
+    private val employees = flow {
+        emit(Employee("Frodo"))
+        emit(Employee("Bilbo"))
+    }
+
+    @Test // #1213
+    fun `Kotlin Flows should render as CollectionModels`() {
+
+        val testResourceAssembler = SimpleTestResourceAssembler()
+        val exchange = mockk<ServerWebExchange>()
+
+        runBlocking {
+            val collectionModel = testResourceAssembler.toCollectionModel(employees, exchange)
+
+            assertThat(collectionModel.links).containsExactly(Link.of("/employees"))
+        }
+    }
+
+    class SimpleTestResourceAssembler : SimpleReactiveRepresentationModelAssembler<Employee> {
+        override fun addLinks(resources: CollectionModel<EntityModel<Employee>>, exchange: ServerWebExchange): CollectionModel<EntityModel<Employee>> {
+            resources.add(Link.of("/employees"))
+            return resources
+        }
+    }
+
+    data class Employee(val name: String)
+
+}