[DO NOT MERGE YET] GH-3103: Introduce CloudEvents transformers

build.gradle

@@ -51,6 +51,7 @@ ext {
 	assertjVersion = '3.15.0'
 	assertkVersion = '0.22'
 	awaitilityVersion = '4.0.2'
+	cloudEventsVersion = '1.3.0'
 	commonsDbcp2Version = '2.7.0'
 	commonsIoVersion = '2.6'
 	commonsNetVersion = '3.6'
@@ -419,6 +420,7 @@ project('spring-integration-core') {
 		optionalApi "io.github.resilience4j:resilience4j-ratelimiter:$resilience4jVersion"
 		optionalApi "org.apache.avro:avro:$avroVersion"
 		optionalApi 'org.jetbrains.kotlin:kotlin-stdlib-jdk8'
+		optionalApi "io.cloudevents:cloudevents-api:$cloudEventsVersion"
 
 		testImplementation ("org.aspectj:aspectjweaver:$aspectjVersion")
 		testImplementation ('com.fasterxml.jackson.datatype:jackson-datatype-jsr310')

spring-integration-core/src/main/java/org/springframework/integration/support/cloudevents/CloudEventHeaders.java

@@ -0,0 +1,79 @@
+/*
+ * 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.integration.support.cloudevents;
+
+/**
+ * Message headers for basic cloud event attributes.
+ * These headers might be remapped to respective attributes/headers
+ * in the target protocol binder.
+ *
+ * @author Artem Bilan
+ *
+ * @since 5.3
+ */
+public final class CloudEventHeaders {
+
+	private CloudEventHeaders() {
+	}
+
+	/**
+	 * Header prefix as a {@value PREFIX} for cloud event attributes.
+	 */
+	public static final String PREFIX = "ce_";
+
+	/**
+	 * The header name for cloud event {@code id} attribute.
+	 */
+	public static final String ID = PREFIX + "id";
+
+	/**
+	 * The header name for cloud event {@code source} attribute.
+	 */
+	public static final String SOURCE = PREFIX + "source";
+
+	/**
+	 * The header name for cloud event {@code specversion} attribute.
+	 */
+	public static final String SPEC_VERSION = PREFIX + "specversion";
+
+	/**
+	 * The header name for cloud event {@code type} attribute.
+	 */
+	public static final String TYPE = PREFIX + "type";
+
+	/**
+	 * The header name for cloud event {@code datacontenttype} attribute.
+	 */
+	public static final String DATA_CONTENT_TYPE = PREFIX + "datacontenttype";
+
+	/**
+	 * The header name for cloud event {@code dataschema} attribute.
+	 */
+	public static final String DATA_SCHEMA = PREFIX + "dataschema";
+
+	/**
+	 * The header name for cloud event {@code subject} attribute.
+	 */
+	public static final String SUBJECT = PREFIX + "subject";
+
+	/**
+	 * The header name for cloud event {@code time} attribute.
+	 */
+	public static final String TIME = PREFIX + "time";
+
+
+}

spring-integration-core/src/main/java/org/springframework/integration/support/cloudevents/ContentTypeDelegatingDataMarshaller.java

@@ -0,0 +1,96 @@
+/*
+ * 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.integration.support.cloudevents;
+
+import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+
+import org.springframework.core.ResolvableType;
+import org.springframework.core.codec.CharSequenceEncoder;
+import org.springframework.core.codec.Encoder;
+import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.core.io.buffer.DataBufferFactory;
+import org.springframework.core.io.buffer.DefaultDataBufferFactory;
+import org.springframework.messaging.MessageHeaders;
+import org.springframework.util.Assert;
+import org.springframework.util.MimeType;
+
+import io.cloudevents.fun.DataMarshaller;
+import io.cloudevents.json.Json;
+
+/**
+ * A {@link DataMarshaller} implementation for delegating
+ * to the provided {@link Encoder}s according a {@link MessageHeaders#CONTENT_TYPE}
+ * header value.
+ *
+ * @author Artem Bilan
+ *
+ * @since 5.3
+ */
+public class ContentTypeDelegatingDataMarshaller implements DataMarshaller<byte[], Object, String> {
+
+	private final DataBufferFactory dataBufferFactory = new DefaultDataBufferFactory();
+
+	private final List<Encoder<?>> encoders = new ArrayList<>();
+
+	public ContentTypeDelegatingDataMarshaller(Encoder<?>... encoders) {
+		this.encoders.add(CharSequenceEncoder.allMimeTypes());
+		setEncoders(encoders);
+	}
+
+	public final void setEncoders(Encoder<?>... encoders) {
+		Assert.notNull(encoders, "'encoders' must not be null");
+		Assert.noNullElements(encoders, "'encoders' must not contain null elements");
+		this.encoders.addAll(Arrays.asList(encoders));
+	}
+
+	@Override
+	@SuppressWarnings({ "unchecked", "rawtypes" })
+	public byte[] marshal(Object data, Map<String, String> headers) throws RuntimeException {
+		String contentType = headers.get(MessageHeaders.CONTENT_TYPE);
+		if (contentType == null) { // Assume JSON by default
+			return Json.binaryMarshal(data, headers);
+		}
+		else {
+			ResolvableType elementType = ResolvableType.forClass(data.getClass());
+			MimeType mimeType = MimeType.valueOf(contentType);
+			Encoder<Object> encoder = encoder(elementType, mimeType);
+			DataBuffer dataBuffer =
+					encoder.encodeValue(data, this.dataBufferFactory, elementType,
+							mimeType, (Map<String, Object>) (Map) headers);
+
+			ByteBuffer buf = dataBuffer.asByteBuffer();
+			byte[] result = new byte[buf.remaining()];
+			buf.get(result);
+			return result;
+		}
+	}
+
+	@SuppressWarnings("unchecked")
+	private Encoder<Object> encoder(ResolvableType elementType, MimeType mimeType) {
+		for (Encoder<?> encoder : this.encoders) {
+			if (encoder.canEncode(elementType, mimeType)) {
+				return (Encoder<Object>) encoder;
+			}
+		}
+		throw new IllegalArgumentException("No encoder for " + elementType);
+	}
+
+}

spring-integration-core/src/main/java/org/springframework/integration/support/cloudevents/HeaderMapper.java

@@ -0,0 +1,80 @@
+/*
+ * 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.integration.support.cloudevents;
+
+import java.util.AbstractMap;
+import java.util.Locale;
+import java.util.Map;
+import java.util.Optional;
+import java.util.stream.Collectors;
+
+import org.springframework.messaging.MessageHeaders;
+import org.springframework.util.Assert;
+
+import io.cloudevents.v1.ContextAttributes;
+
+/**
+ * A Cloud Event header mapper.
+ *
+ * @author Artem Bilan
+ *
+ * @since 5.3
+ */
+public final class HeaderMapper {
+
+	/**
+	 * Following the signature of {@link io.cloudevents.fun.FormatHeaderMapper}
+	 * @param attributes The map of attributes
+	 * @param extensions The map of extensions
+	 * @return The map of headers
+	 */
+	public static Map<String, String> map(Map<String, String> attributes, Map<String, String> extensions) {
+		Assert.notNull(attributes, "'attributes' must not be null");
+		Assert.notNull(extensions, "'extensions' must not be null");
+
+		Map<String, String> result =
+				attributes.entrySet()
+						.stream()
+						.filter(attribute ->
+								attribute.getValue() != null
+										&& !ContextAttributes.datacontenttype.name().equals(attribute.getKey()))
+						.map(header ->
+								new AbstractMap.SimpleEntry<>(
+										CloudEventHeaders.PREFIX + header.getKey().toLowerCase(Locale.US),
+										header.getValue()))
+						.collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
+
+		result.putAll(
+				extensions.entrySet()
+						.stream()
+						.filter(extension -> extension.getValue() != null)
+						.collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue))
+		);
+
+		Optional.ofNullable(attributes
+				.get(ContextAttributes.datacontenttype.name()))
+				.ifPresent((dataContentType) -> {
+					result.put(MessageHeaders.CONTENT_TYPE, dataContentType);
+				});
+
+		return result;
+	}
+
+	private HeaderMapper() {
+	}
+
+}

spring-integration-core/src/main/java/org/springframework/integration/support/cloudevents/Marshallers.java

@@ -0,0 +1,96 @@
+/*
+ * 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.integration.support.cloudevents;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import org.springframework.messaging.MessageHeaders;
+
+import io.cloudevents.extensions.ExtensionFormat;
+import io.cloudevents.format.BinaryMarshaller;
+import io.cloudevents.format.StructuredMarshaller;
+import io.cloudevents.format.Wire;
+import io.cloudevents.format.builder.EventStep;
+import io.cloudevents.fun.DataMarshaller;
+import io.cloudevents.json.Json;
+import io.cloudevents.v1.Accessor;
+import io.cloudevents.v1.AttributesImpl;
+
+/**
+ * A Cloud Events  general purpose marshallers factory.
+ *
+ * @author Artem Bilan
+ *
+ * @since 5.3
+ */
+public final class Marshallers {
+
+	private static final Map<String, String> NO_HEADERS = new HashMap<>();
+
+	/**
+	 * Builds a Binary Content Mode marshaller to marshal cloud events as JSON for
+	 * any Transport Binding.
+	 * @param <T> The data type
+	 * @return a builder to provide the {@link io.cloudevents.CloudEvent} and marshal as JSON
+	 * @see BinaryMarshaller
+	 */
+	public static <T> EventStep<AttributesImpl, T, byte[], String> binary() {
+		return binary(Json::binaryMarshal);
+	}
+
+	/**
+	 * Builds a Binary Content Mode marshaller to marshal cloud events as a {@code byte[]} for
+	 * any Transport Binding.
+	 * The data marshalling is based on the provided {@link DataMarshaller}.
+	 * @param marshaller the {@link DataMarshaller} for cloud event payload.
+	 * @param <T> The data type
+	 * @return a builder to provide the {@link io.cloudevents.CloudEvent} and marshal as JSON
+	 * @see BinaryMarshaller
+	 */
+	public static <T> EventStep<AttributesImpl, T, byte[], String> binary(
+			DataMarshaller<byte[], T, String> marshaller) {
+
+		return BinaryMarshaller.<AttributesImpl, T, byte[], String>builder()
+				.map(AttributesImpl::marshal)
+				.map(Accessor::extensionsOf)
+				.map(ExtensionFormat::marshal)
+				.map(HeaderMapper::map)
+				.map(marshaller)
+				.builder(Wire::new);
+	}
+
+	/**
+	 * Builds a Structured Content Mode marshaller to marshal cloud event as JSON for
+	 * any Transport Binding.
+	 * @param <T> The data type
+	 * @return a builder to provide the {@link io.cloudevents.CloudEvent} and marshal as JSON
+	 * @see StructuredMarshaller
+	 */
+	public static <T> EventStep<AttributesImpl, T, byte[], String> structured() {
+		return StructuredMarshaller.<AttributesImpl, T, byte[], String>
+				builder()
+				.mime(MessageHeaders.CONTENT_TYPE, "application/cloudevents+json")
+				.map((event) -> Json.binaryMarshal(event, NO_HEADERS))
+				.skip();
+	}
+
+	private Marshallers() {
+
+	}
+
+}

spring-integration-core/src/main/java/org/springframework/integration/support/cloudevents/package-info.java

@@ -0,0 +1,4 @@
+/**
+ * Provides classes to support for Cloud Events.
+ */
+package org.springframework.integration.support.cloudevents;