Updated JavaDoc.

spring-eai-core/src/main/java/org/springframework/eai/message/DocumentMessage.java

@@ -17,6 +17,9 @@
 package org.springframework.eai.message;
 
 /**
+ * A simple Message implementation that encapsulates
+ * a single Object as its payload.
+ *
  * @author Mark Fisher
  */
 public class DocumentMessage implements Message {

spring-eai-core/src/main/java/org/springframework/eai/message/Message.java

@@ -17,6 +17,8 @@
 package org.springframework.eai.message;
 
 /**
+ * The central interface that any Message type must implement.
+ * 
  * @author Mark Fisher
  */
 public interface Message {

spring-eai-core/src/main/java/org/springframework/eai/message/MessageHeader.java

@@ -21,6 +21,13 @@ import java.util.Properties;
 import java.util.concurrent.ConcurrentHashMap;
 
 /**
+ * A holder for Message metadata. This includes information
+ * that is used by the messaging system (such as <i>id</i>
+ * and <i>correlationId</i>) as well as information that
+ * is relevant for specific messaging endpoints. For the
+ * latter, String values may be stored as <i>properties</i>
+ * and Object values may be stored as <i>attributes</i>.
+ * 
  * @author Mark Fisher
  */
 public class MessageHeader {