spring-projectsGH-1549: Auto-Detect Type Mappings

Resolves  spring-projects#1549

spring-kafka/src/main/java/org/springframework/kafka/annotation/TypeMapping.java

@@ -0,0 +1,48 @@
+/*
+ * 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.kafka.annotation;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * TODO: Move to spring-messaging?
+ *
+ * Classes annotated with this can be automatically populated into various type mappers
+ * (e.g. Jackson). Several Spring projects, JMS, Kafka, RabbitMQ allow mapping a type id
+ * to/from a class, for the purpose of decoupling concrete types used by senders and
+ * receivers.
+ *
+ * @author Gary Russell
+ * @since 2.6
+ *
+ */
+@Target(ElementType.TYPE)
+@Retention(RetentionPolicy.RUNTIME)
+@Documented
+public @interface TypeMapping {
+
+	/**
+	 * Either a single or multiple type ids to map to/from the annotated class.
+	 * @return the type ids.
+	 */
+	String[] value();
+
+}

spring-kafka/src/main/java/org/springframework/kafka/support/TypeMappingUtils.java

@@ -0,0 +1,87 @@
+/*
+ * 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.kafka.support;
+
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+
+import org.springframework.beans.factory.config.BeanDefinition;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider;
+import org.springframework.core.annotation.AnnotatedElementUtils;
+import org.springframework.core.annotation.AnnotationAttributes;
+import org.springframework.core.type.filter.AnnotationTypeFilter;
+import org.springframework.kafka.annotation.TypeMapping;
+import org.springframework.util.ClassUtils;
+import org.springframework.util.StringUtils;
+
+/**
+ * TODO: Move to spring-messaging?
+ *
+ * Utilities for type mappings.
+ *
+ * @author Gary Russell
+ * @since 2.6
+ *
+ */
+public final class TypeMappingUtils {
+
+	private TypeMappingUtils() {
+	}
+
+	/**
+	 * Find {@link TypeMapping} annotations on classes in the provided packages and return
+	 * as a map of typeid:class.
+	 * @param context the application context.
+	 * @param packagesToScan the packages to scan.
+	 * @return the mappings.
+	 */
+	public static Map<String, Class<?>> findTypeMappings(ApplicationContext context, String... packagesToScan) {
+
+		Map<String, Class<?>> mappings = new HashMap<>();
+		Set<Class<?>> candidates = new HashSet<>();
+		ClassPathScanningCandidateComponentProvider scanner = new ClassPathScanningCandidateComponentProvider(false);
+		scanner.setEnvironment(context.getEnvironment());
+		scanner.setResourceLoader(context);
+		scanner.addIncludeFilter(new AnnotationTypeFilter(TypeMapping.class));
+		for (String packageToScan : packagesToScan) {
+			if (StringUtils.hasText(packageToScan)) {
+				for (BeanDefinition candidate : scanner.findCandidateComponents(packageToScan)) {
+					try {
+						candidates.add(ClassUtils.forName(candidate.getBeanClassName(), context.getClassLoader()));
+					}
+					catch (ClassNotFoundException | LinkageError e) {
+						throw new IllegalStateException(e);
+					}
+				}
+			}
+		}
+		for (Class<?> candidate : candidates) {
+			AnnotationAttributes annotationAttributes =
+					AnnotatedElementUtils.findMergedAnnotationAttributes(candidate, TypeMapping.class, false, false);
+			for (String  value : annotationAttributes.getStringArray("value")) {
+				if (StringUtils.hasText(value)) {
+					mappings.put(value, candidate);
+				}
+			}
+		}
+		return mappings;
+	}
+
+}

spring-kafka/src/test/java/org/springframework/kafka/support/TypeMappingUtilsTests.java

@@ -0,0 +1,61 @@
+/*
+ * 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.kafka.support;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.Map;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.context.support.GenericApplicationContext;
+import org.springframework.kafka.annotation.TypeMapping;
+
+/**
+ * TODO: Move to spring-messaging?
+ *
+ * @author Gary Russell
+ * @since 2.6
+ *
+ */
+public class TypeMappingUtilsTests {
+
+	@Test
+	void testDiscover() {
+		Map<String, Class<?>> mappings =
+				TypeMappingUtils.findTypeMappings(new GenericApplicationContext(), getClass().getPackage().getName());
+		assertThat(mappings).hasSize(6); // this will be 3 if we move this to s-m
+		assertThat(mappings.get("fooA")).isEqualTo(Foo.class);
+		assertThat(mappings.get("fooB")).isEqualTo(Foo.class);
+		assertThat(mappings.get("barA")).isEqualTo(Bar.class);
+	}
+
+	@TypeMapping({ "fooA", "fooB" })
+	public static class Foo {
+
+		public String foo = "foo";
+
+	}
+
+	@TypeMapping("barA")
+	public static class Bar extends Foo {
+
+		public String bar = "bar";
+
+	}
+
+}

spring-kafka/src/test/java/org/springframework/kafka/support/serializer/JsonSerializationTests.java

@@ -30,12 +30,16 @@
 
 import org.apache.kafka.common.errors.SerializationException;
 import org.apache.kafka.common.header.Headers;
+import org.apache.kafka.common.header.internals.RecordHeader;
 import org.apache.kafka.common.header.internals.RecordHeaders;
 import org.apache.kafka.common.serialization.StringDeserializer;
 import org.apache.kafka.common.serialization.StringSerializer;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
+import org.springframework.context.support.GenericApplicationContext;
+import org.springframework.kafka.annotation.TypeMapping;
+import org.springframework.kafka.support.TypeMappingUtils;
 import org.springframework.kafka.support.converter.AbstractJavaTypeMapper;
 import org.springframework.kafka.support.converter.DefaultJackson2JavaTypeMapper;
 import org.springframework.kafka.support.converter.Jackson2JavaTypeMapper.TypePrecedence;
@@ -335,6 +339,26 @@ void testTypeResolverDirect() {
 		deser.close();
 	}
 
+	@Test
+	void testDiscoveredTypeMappings() {
+		DefaultJackson2JavaTypeMapper mapper = new DefaultJackson2JavaTypeMapper();
+		GenericApplicationContext context = new GenericApplicationContext();
+		mapper.setTypePrecedence(TypePrecedence.TYPE_ID);
+		mapper.setIdClassMapping(TypeMappingUtils.findTypeMappings(context, getClass().getPackage().getName()));
+		JsonDeserializer<Object> deser = new JsonDeserializer<>()
+				.trustedPackages("*")
+				.typeMapper(mapper);
+		Headers headers = new RecordHeaders();
+		headers.add(new RecordHeader(AbstractJavaTypeMapper.DEFAULT_CLASSID_FIELD_NAME, "foo1".getBytes()));
+		assertThat(deser.deserialize("", headers, "{\"foo\":\"bar\"}".getBytes())).isInstanceOf(Foo.class);
+		headers.add(new RecordHeader(AbstractJavaTypeMapper.DEFAULT_CLASSID_FIELD_NAME, "foo2".getBytes()));
+		assertThat(deser.deserialize("", headers, "{\"foo\":\"bar\"}".getBytes())).isInstanceOf(Foo.class);
+		headers.add(new RecordHeader(AbstractJavaTypeMapper.DEFAULT_CLASSID_FIELD_NAME, "bar".getBytes()));
+		assertThat(deser.deserialize("", headers, "{\"bar\":\"baz\"}".getBytes()))
+				.isInstanceOf(Bar.class);
+		deser.close();
+	}
+
 	public static JavaType fooBarJavaType(byte[] data, Headers headers) {
 		if (data[0] == '{' && data[1] == 'f') {
 			return TypeFactory.defaultInstance().constructType(Foo.class);
@@ -369,12 +393,14 @@ static class DummyEntityArrayJsonDeserializer extends JsonDeserializer<DummyEnti
 
 	}
 
+	@TypeMapping({ "foo1", "foo2" })
 	public static class Foo {
 
 		public String foo = "foo";
 
 	}
 
+	@TypeMapping("bar")
 	public static class Bar extends Foo {
 
 		public String bar = "bar";