INT-4451: ObjectToJsonTrans: add ResultType.BYTES

JIRA: https://jira.spring.io/browse/INT-4451

Author: artembilan

spring-integration-core/src/main/java/org/springframework/integration/json/ObjectToJsonTransformer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -16,7 +16,10 @@
 
 package org.springframework.integration.json;
 
-import org.springframework.integration.support.AbstractIntegrationMessageBuilder;
+import java.io.ByteArrayOutputStream;
+import java.io.OutputStreamWriter;
+import java.util.Map;
+
 import org.springframework.integration.support.json.JsonObjectMapper;
 import org.springframework.integration.support.json.JsonObjectMapperProvider;
 import org.springframework.integration.transformer.AbstractTransformer;
@@ -52,12 +55,13 @@
  * @author Oleg Zhurakousky
  * @author Gary Russell
  * @author Artem Bilan
+ *
  * @since 2.0
  */
 public class ObjectToJsonTransformer extends AbstractTransformer {
 
 	public enum ResultType {
-		STRING, NODE
+		STRING, NODE, BYTES
 	}
 
 	public static final String JSON_CONTENT_TYPE = "application/json";
@@ -108,12 +112,9 @@ public String getComponentType() {
 
 	@Override
 	protected Object doTransform(Message<?> message) throws Exception {
-		Object payload = ResultType.STRING.equals(this.resultType)
-				? this.jsonObjectMapper.toJson(message.getPayload())
-				: this.jsonObjectMapper.toJsonNode(message.getPayload());
-		AbstractIntegrationMessageBuilder<Object> messageBuilder = this.getMessageBuilderFactory().withPayload(payload);
+		Object payload = buildJsonPayload(message.getPayload());
 
-		LinkedCaseInsensitiveMap<Object> headers = new LinkedCaseInsensitiveMap<Object>();
+		Map<String, Object> headers = new LinkedCaseInsensitiveMap<>();
 		headers.putAll(message.getHeaders());
 
 		if (headers.containsKey(MessageHeaders.CONTENT_TYPE)) {
@@ -130,8 +131,30 @@ else if (StringUtils.hasLength(this.contentType)) {
 
 		this.jsonObjectMapper.populateJavaTypes(headers, message.getPayload());
 
-		messageBuilder.copyHeaders(headers);
-		return messageBuilder.build();
+		return getMessageBuilderFactory()
+				.withPayload(payload)
+				.copyHeaders(headers)
+				.build();
+	}
+
+	private Object buildJsonPayload(Object payload) throws Exception {
+		switch (this.resultType) {
+
+			case STRING:
+				return this.jsonObjectMapper.toJson(payload);
+
+			case NODE:
+				return this.jsonObjectMapper.toJsonNode(payload);
+
+			case BYTES:
+				try (ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
+					this.jsonObjectMapper.toJson(payload, new OutputStreamWriter(baos));
+					return baos.toByteArray();
+				}
+
+			default:
+				throw new IllegalArgumentException("Unsupported ResultType provided: " + this.resultType);
+		}
 	}
 
 }

spring-integration-core/src/main/resources/org/springframework/integration/config/spring-integration-5.1.xsd

@@ -2591,6 +2591,7 @@
 		<xsd:restriction base="xsd:token">
 			<xsd:enumeration value="STRING" />
 			<xsd:enumeration value="NODE" />
+			<xsd:enumeration value="BYTES" />
 		</xsd:restriction>
 	</xsd:simpleType>
 

spring-integration-core/src/test/java/org/springframework/integration/json/ObjectToJsonTransformerTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -52,6 +52,7 @@
  * @author Oleg Zhurakousky
  * @author Gary Russell
  * @author Artem Bilan
+ *
  * @since 2.0
  */
 public class ObjectToJsonTransformerTests {
@@ -118,6 +119,14 @@ public void simpleIntegerPayload() throws Exception {
 		assertEquals("123", result);
 	}
 
+	@Test
+	public void simpleIntegerAsBytesPayload() {
+		ObjectToJsonTransformer transformer = new ObjectToJsonTransformer(ObjectToJsonTransformer.ResultType.BYTES);
+		Object result = transformer.transform(new GenericMessage<>(123)).getPayload();
+		assertThat(result, instanceOf(byte[].class));
+		assertEquals("123", new String((byte[]) result));
+	}
+
 	@Test
 	public void objectPayload() throws Exception {
 		ObjectToJsonTransformer transformer = new ObjectToJsonTransformer();

src/reference/asciidoc/transformer.adoc

@@ -382,6 +382,8 @@ The node JSON representation provides efficiency for using the `JsonPropertyAcce
 See <<spel-property-accessors>>.
 When using Boon, the `NODE` representation is a `Map<String, Object>`
 
+Beginning with _version 5.1_, the `resultType` can be configured as `BYTES` to produce a message with the `byte[]` payload for convenience in downstream handlers which operate with this data type.
+
 [[transformer-annotation]]
 ===== Configuring a Transformer with Annotations
 

src/reference/asciidoc/whats-new.adoc

@@ -38,3 +38,9 @@ Previously:
 
 Global channel interceptors are now applied to channels registered dynamically - such as via the `IntegrationFlowContext` when using the Java DSL, or beans that are initialized using `beanFactory.initializeBean()`.
 Previously, interceptors were not applied when beans were created after the application context was refreshed.
+
+==== ObjectToJsonTransformer
+
+A new `ResultType.BYTES` mode is introduced for the `ObjectToJsonTransformer`.
+
+See <<json-transformers>> for more information.