Add converter for Object->String conversion

Support `text/plain` outbound content type for generic objects

Fix #774

spring-cloud-stream-integration-tests/src/test/java/org/springframework/cloud/stream/config/TextPlainConversionTest.java

@@ -0,0 +1,111 @@
+/*
+ * 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.cloud.stream.config;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.concurrent.TimeUnit;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.cloud.stream.annotation.EnableBinding;
+import org.springframework.cloud.stream.binder.BinderFactory;
+import org.springframework.cloud.stream.messaging.Processor;
+import org.springframework.cloud.stream.test.binder.TestSupportBinder;
+import org.springframework.context.annotation.PropertySource;
+import org.springframework.integration.annotation.ServiceActivator;
+import org.springframework.integration.support.MessageBuilder;
+import org.springframework.messaging.Message;
+import org.springframework.messaging.MessageChannel;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+
+/**
+ * @author Marius Bogoevici
+ *
+ * @since 1.2
+ */
+@RunWith(SpringJUnit4ClassRunner.class)
+@SpringBootTest(classes = TextPlainConversionTest.FooProcessor.class)
+public class TextPlainConversionTest {
+
+	@Autowired
+	private Processor testProcessor;
+
+	@Autowired
+	private BinderFactory binderFactory;
+
+	@Test
+	public void testTextPlainConversionOnOutput() throws Exception {
+		testProcessor.input().send(MessageBuilder.withPayload("Bar").build());
+		@SuppressWarnings("unchecked")
+		Message<?> received = ((TestSupportBinder) binderFactory.getBinder(null, MessageChannel.class))
+				.messageCollector().forChannel(testProcessor.output()).poll(1, TimeUnit.SECONDS);
+		assertThat(received).isNotNull();
+		assertThat(received.getPayload()).isEqualTo("Foo{name='Bar'}");
+	}
+
+	@Test
+	public void testTextPlainConversionOnInputAndOutput() throws Exception {
+		testProcessor.input().send(MessageBuilder.withPayload(new Foo("Bar")).build());
+		@SuppressWarnings("unchecked")
+		Message<?> received = ((TestSupportBinder) binderFactory.getBinder(null, MessageChannel.class))
+				.messageCollector().forChannel(testProcessor.output()).poll(1, TimeUnit.SECONDS);
+		assertThat(received).isNotNull();
+		assertThat(received.getPayload()).isEqualTo("Foo{name='Foo{name='Bar'}'}");
+	}
+
+
+	@EnableBinding(Processor.class)
+	@EnableAutoConfiguration
+	@PropertySource("classpath:/org/springframework/cloud/stream/config/textplain/text-plain.properties")
+	public static class FooProcessor {
+
+		@ServiceActivator(inputChannel = "input", outputChannel = "output")
+		public Foo consume(String foo) {
+			return new Foo(foo);
+		}
+
+	}
+
+	public static class Foo {
+
+		private String name;
+
+		public Foo(String name) {
+			this.name = name;
+		}
+
+		public String getName() {
+			return name;
+		}
+
+		public void setName(String name) {
+			this.name = name;
+		}
+
+		@Override
+		public String toString() {
+			return "Foo{name='" + name + "'}";
+		}
+
+	}
+
+}

spring-cloud-stream-integration-tests/src/test/resources/org/springframework/cloud/stream/config/textplain/text-plain.properties

@@ -0,0 +1,2 @@
+spring.cloud.stream.bindings.input.content-type=text/plain
+spring.cloud.stream.bindings.output.content-type=text/plain

spring-cloud-stream/src/main/java/org/springframework/cloud/stream/converter/CompositeMessageConverterFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2015-2016 the original author or authors.
+ * Copyright 2015-2017 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.
@@ -29,7 +29,6 @@ import org.springframework.messaging.converter.ByteArrayMessageConverter;
 import org.springframework.messaging.converter.CompositeMessageConverter;
 import org.springframework.messaging.converter.MappingJackson2MessageConverter;
 import org.springframework.messaging.converter.MessageConverter;
-import org.springframework.messaging.converter.StringMessageConverter;
 import org.springframework.util.CollectionUtils;
 import org.springframework.util.MimeType;
 
@@ -79,8 +78,7 @@ public class CompositeMessageConverterFactory {
 
 		this.converters.add(jsonMessageConverter);
 		this.converters.add(new ByteArrayMessageConverter());
-
-		this.converters.add(new StringMessageConverter());
+		this.converters.add(new ObjectStringMessageConverter());
 		this.converters.add(new JavaSerializationMessageConverter());
 		this.converters.add(new JsonUnmarshallingConverter(this.objectMapper));
 	}

spring-cloud-stream/src/main/java/org/springframework/cloud/stream/converter/ObjectStringMessageConverter.java

@@ -0,0 +1,68 @@
+/*
+ * 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.cloud.stream.converter;
+
+import java.nio.charset.Charset;
+
+import org.springframework.messaging.Message;
+import org.springframework.messaging.MessageHeaders;
+import org.springframework.messaging.converter.AbstractMessageConverter;
+import org.springframework.util.MimeType;
+
+/**
+ * A {@link org.springframework.messaging.converter.MessageConverter} to convert a
+ * non-String objects to a String, when expected content type is "text/plain".
+ * 
+ * It only performs conversions to internal format and is a wrapper
+ * around {@link Object#toString()}.
+ * 
+ * @author Marius Bogoevici
+ *
+ * @since 1.2
+ */
+public class ObjectStringMessageConverter extends AbstractMessageConverter {
+
+	public ObjectStringMessageConverter() {
+		super(new MimeType("text", "plain", Charset.forName("UTF-8")));
+	}
+
+	protected boolean supports(Class<?> clazz) {
+		return true;
+	}
+
+	protected Object convertFromInternal(Message<?> message, Class<?> targetClass, Object conversionHint) {
+		if (message.getPayload() != null) {
+			if (message.getPayload() instanceof byte[]) {
+				return new String((byte[]) message.getPayload(), Charset.forName("UTF-8"));
+			}
+			else {
+				return message.getPayload().toString();
+			}
+		}
+		return null;
+	}
+
+	protected Object convertToInternal(Object payload, MessageHeaders headers, Object conversionHint) {
+		if (payload != null) {
+			return payload.toString();
+		}
+		else {
+			return null;
+		}
+	}
+
+}