DATACMNS-1171 - Limit Kotlin reflection support to regular classes.

We now only inspect regular Kotlin classes with inspection to adapt Kotlin-specific behavior. Multipart-, synthetic and unknown classes are not supported. In such cases we fall back to the JVM reflection mechanism.

Non-regular classes are typically synthetic stubs, lambdas and SAM conversion which do not represent typical domain objects but rather technical bridge code.

Original pull request: #245.

src/test/java/org/springframework/data/util/ReflectionUtilsUnitTests.java

@@ -24,12 +24,16 @@ import org.junit.Before;
 import org.junit.Test;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.core.MethodParameter;
+import org.springframework.data.mapping.model.TypeCreatingSyntheticClassKt;
 import org.springframework.data.repository.sample.User;
 import org.springframework.data.util.ReflectionUtils.DescribedFieldFilter;
 import org.springframework.util.ReflectionUtils.FieldFilter;
 
 /**
+ * Unit tests for {@link ReflectionUtils}.
+ *
  * @author Oliver Gierke
+ * @author Mark Paluch
  */
 public class ReflectionUtilsUnitTests {
 
@@ -143,6 +147,20 @@ public class ReflectionUtilsUnitTests {
 		MethodParameter parameter = new MethodParameter(DummyInterface.class.getDeclaredMethod("primitive", int.class), 0);
 		assertThat(ReflectionUtils.isNullable(parameter)).isFalse();
 	}
+	
+	@Test // DATACMNS-1171
+	public void discoversKotlinClass() {
+
+		assertThat(ReflectionUtils.isKotlinClass(TypeCreatingSyntheticClass.class)).isTrue();
+		assertThat(ReflectionUtils.isSupportedKotlinClass(TypeCreatingSyntheticClass.class)).isTrue();
+	}
+	
+	@Test // DATACMNS-1171
+	public void discoversUnsupportedKotlinClass() {
+
+		assertThat(ReflectionUtils.isKotlinClass(TypeCreatingSyntheticClassKt.class)).isTrue();
+		assertThat(ReflectionUtils.isSupportedKotlinClass(TypeCreatingSyntheticClassKt.class)).isFalse();
+	}
 
 	static class Sample {
 

src/test/kotlin/org/springframework/data/mapping/model/PreferredConstructorDiscovererUnitTests.kt

@@ -74,6 +74,17 @@ class PreferredConstructorDiscovererUnitTests {
 
 		Assertions.assertThat(constructor.parameters.size).isEqualTo(3)
 	}
+	
+	@Test // DATACMNS-1171
+	@Suppress("UNCHECKED_CAST")
+	fun `should not resolve constructor for synthetic Kotlin class`() {
+
+		val c = Class.forName("org.springframework.data.mapping.model.TypeCreatingSyntheticClassKt") as Class<Any>
+		
+		val constructor = PreferredConstructorDiscoverer.discover<Any, SamplePersistentProperty>(c)
+
+		Assertions.assertThat(constructor).isNull()
+	}
 
 	data class Simple(val firstname: String)
 

src/test/kotlin/org/springframework/data/mapping/model/TypeCreatingSyntheticClass.kt

@@ -0,0 +1,25 @@
+/*
+ * Copyright 2017 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
+ *
+ *      http://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.data.mapping.model
+
+/**
+ * @author Mark Paluch
+ */
+class TypeCreatingSyntheticClass {
+}
+
+fun foobar(args: Array<String>) {
+}

src/test/kotlin/org/springframework/data/util/TypeCreatingSyntheticClass.kt

@@ -0,0 +1,25 @@
+/*
+ * Copyright 2017 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
+ *
+ *      http://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.data.util
+
+/**
+ * @author Mark Paluch
+ */
+class TypeCreatingSyntheticClass {
+}
+
+fun foobar(args: Array<String>) {
+}