MutableMessageHeaders serializes itself as regular MessageHeaders

Issue: SPR-15262
(cherry picked from commit 74bdcd8)

Author: jhoeller

spring-messaging/src/main/java/org/springframework/messaging/support/MessageHeaderAccessor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -135,19 +135,15 @@ public class MessageHeaderAccessor {
 	 * A constructor to create new headers.
 	 */
 	public MessageHeaderAccessor() {
-		this.headers = new MutableMessageHeaders();
+		this(null);
 	}
 
 	/**
 	 * A constructor accepting the headers of an existing message to copy.
+	 * @param message a message to copy the headers from, or {@code null} if none
 	 */
 	public MessageHeaderAccessor(Message<?> message) {
-		if (message != null) {
-			this.headers = new MutableMessageHeaders(message.getHeaders());
-		}
-		else {
-			this.headers = new MutableMessageHeaders();
-		}
+		this.headers = new MutableMessageHeaders(message != null ? message.getHeaders() : null);
 	}
 
 
@@ -192,7 +188,6 @@ public void setLeaveMutable(boolean leaveMutable) {
 	 * @since 4.1
 	 */
 	public void setImmutable() {
-		this.headers.setIdAndTimestamp();
 		this.headers.setImmutable();
 	}
 
@@ -582,7 +577,7 @@ public static <T extends MessageHeaderAccessor> T getAccessor(
 
 		if (messageHeaders instanceof MutableMessageHeaders) {
 			MutableMessageHeaders mutableHeaders = (MutableMessageHeaders) messageHeaders;
-			MessageHeaderAccessor headerAccessor = mutableHeaders.getMessageHeaderAccessor();
+			MessageHeaderAccessor headerAccessor = mutableHeaders.getAccessor();
 			if (requiredType.isAssignableFrom(headerAccessor.getClass()))  {
 				return (T) headerAccessor;
 			}
@@ -602,7 +597,7 @@ public static <T extends MessageHeaderAccessor> T getAccessor(
 	public static MessageHeaderAccessor getMutableAccessor(Message<?> message) {
 		if (message.getHeaders() instanceof MutableMessageHeaders) {
 			MutableMessageHeaders mutableHeaders = (MutableMessageHeaders) message.getHeaders();
-			MessageHeaderAccessor accessor = mutableHeaders.getMessageHeaderAccessor();
+			MessageHeaderAccessor accessor = mutableHeaders.getAccessor();
 			if (accessor != null) {
 				return (accessor.isMutable() ? accessor : accessor.createAccessor(message));
 			}
@@ -614,38 +609,23 @@ public static MessageHeaderAccessor getMutableAccessor(Message<?> message) {
 	@SuppressWarnings("serial")
 	private class MutableMessageHeaders extends MessageHeaders {
 
-		private boolean immutable;
-
-		public MutableMessageHeaders() {
-			this(null);
-		}
+		private boolean mutable = true;
 
 		public MutableMessageHeaders(Map<String, Object> headers) {
 			super(headers, MessageHeaders.ID_VALUE_NONE, -1L);
 		}
 
-		public MessageHeaderAccessor getMessageHeaderAccessor() {
-			return MessageHeaderAccessor.this;
-		}
-
 		@Override
 		public Map<String, Object> getRawHeaders() {
-			Assert.state(!this.immutable, "Already immutable");
+			Assert.state(this.mutable, "Already immutable");
 			return super.getRawHeaders();
 		}
 
 		public void setImmutable() {
-			this.immutable = true;
-		}
-
-		public boolean isMutable() {
-			return !this.immutable;
-		}
-
-		public void setIdAndTimestamp() {
-			if (!isMutable()) {
+			if (!this.mutable) {
 				return;
 			}
+
 			if (getId() == null) {
 				IdGenerator idGenerator = (MessageHeaderAccessor.this.idGenerator != null ?
 						MessageHeaderAccessor.this.idGenerator : MessageHeaders.getIdGenerator());
@@ -654,11 +634,27 @@ public void setIdAndTimestamp() {
 					getRawHeaders().put(ID, id);
 				}
 			}
+
 			if (getTimestamp() == null) {
 				if (MessageHeaderAccessor.this.enableTimestamp) {
 					getRawHeaders().put(TIMESTAMP, System.currentTimeMillis());
 				}
 			}
+
+			this.mutable = false;
+		}
+
+		public boolean isMutable() {
+			return this.mutable;
+		}
+
+		public MessageHeaderAccessor getAccessor() {
+			return MessageHeaderAccessor.this;
+		}
+
+		protected Object writeReplace() {
+			// Serialize as regular MessageHeaders (without MessageHeaderAccessor reference)
+			return new MessageHeaders(this);
 		}
 	}
 

spring-messaging/src/test/java/org/springframework/messaging/support/MessageHeaderAccessorTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -17,10 +17,8 @@
 package org.springframework.messaging.support;
 
 import java.nio.charset.Charset;
-import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashMap;
-import java.util.HashSet;
 import java.util.Map;
 import java.util.UUID;
 
@@ -30,8 +28,8 @@
 
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageHeaders;
-import org.springframework.util.IdGenerator;
 import org.springframework.util.MimeTypeUtils;
+import org.springframework.util.SerializationTestUtils;
 
 import static org.hamcrest.CoreMatchers.*;
 import static org.junit.Assert.*;
@@ -168,7 +166,7 @@ public void copyHeadersFromNullMap() {
 		headers.copyHeadersIfAbsent(null);
 
 		assertEquals(1, headers.getMessageHeaders().size());
-		assertEquals(new HashSet<>(Arrays.asList("id")), headers.getMessageHeaders().keySet());
+		assertEquals(Collections.singleton("id"), headers.getMessageHeaders().keySet());
 	}
 
 	@Test
@@ -282,12 +280,7 @@ public void timestampDefaultBehavior() {
 	public void idGeneratorCustom() {
 		final UUID id = new UUID(0L, 23L);
 		MessageHeaderAccessor accessor = new MessageHeaderAccessor();
-		accessor.setIdGenerator(new IdGenerator() {
-			@Override
-			public UUID generateId() {
-				return id;
-			}
-		});
+		accessor.setIdGenerator(() -> id);
 		assertSame(id, accessor.getMessageHeaders().getId());
 	}
 
@@ -301,12 +294,7 @@ public void idGeneratorDefaultBehavior() {
 	@Test
 	public void idTimestampWithMutableHeaders() {
 		MessageHeaderAccessor accessor = new MessageHeaderAccessor();
-		accessor.setIdGenerator(new IdGenerator() {
-			@Override
-			public UUID generateId() {
-				return MessageHeaders.ID_VALUE_NONE;
-			}
-		});
+		accessor.setIdGenerator(() -> MessageHeaders.ID_VALUE_NONE);
 		accessor.setEnableTimestamp(false);
 		accessor.setLeaveMutable(true);
 		MessageHeaders headers = accessor.getMessageHeaders();
@@ -315,12 +303,7 @@ public UUID generateId() {
 		assertNull(headers.getTimestamp());
 
 		final UUID id = new UUID(0L, 23L);
-		accessor.setIdGenerator(new IdGenerator() {
-			@Override
-			public UUID generateId() {
-				return id;
-			}
-		});
+		accessor.setIdGenerator(() -> id);
 		accessor.setEnableTimestamp(true);
 		accessor.setImmutable();
 
@@ -398,10 +381,25 @@ public String toString() {
 		assertEquals("headers={contentType=text/plain} payload=" + sb + " > 80", actual);
 	}
 
+	@Test
+	public void serializeMutableHeaders() throws Exception {
+		Map<String, Object> headers = new HashMap<>();
+		headers.put("foo", "bar");
+		Message<String> message = new GenericMessage<>("test", headers);
+		MessageHeaderAccessor mutableAccessor = MessageHeaderAccessor.getMutableAccessor(message);
+		mutableAccessor.setContentType(MimeTypeUtils.TEXT_PLAIN);
+
+		message = new GenericMessage<>(message.getPayload(), mutableAccessor.getMessageHeaders());
+		Message<?> output = (Message<?>) SerializationTestUtils.serializeAndDeserialize(message);
+		assertEquals("test", output.getPayload());
+		assertEquals("bar", output.getHeaders().get("foo"));
+		assertNotNull(output.getHeaders().get(MessageHeaders.CONTENT_TYPE));
+	}
+
 
 	public static class TestMessageHeaderAccessor extends MessageHeaderAccessor {
 
-		private TestMessageHeaderAccessor() {
+		public TestMessageHeaderAccessor() {
 		}
 
 		private TestMessageHeaderAccessor(Message<?> message) {