Improve AlreadyClosedException error message

 * Fix a couple of issues with prefixes
 * Propagate cause to ACE and use it in the message when it is not null
 * Don't append reason when it is not null
 * Rename "reason" to "protocol method" since in 3.3 it only can be
   a protocol method (and using both reason and cause is confusing)

Author: michaelklishin

src/com/rabbitmq/client/AlreadyClosedException.java

@@ -25,12 +25,21 @@ public class AlreadyClosedException extends ShutdownSignalException {
     /** Default for suppressing warnings without version check. */
     private static final long serialVersionUID = 1L;
 
-    public AlreadyClosedException(ShutdownSignalException sse)
-    {
+    public AlreadyClosedException(ShutdownSignalException sse) {
+        this(sse, null);
+    }
+
+    public AlreadyClosedException(ShutdownSignalException sse, Throwable cause) {
         super(sse.isHardError(),
               sse.isInitiatedByApplication(),
               sse.getReason(),
               sse.getReference(),
-              (sse.isHardError() ? "connection" : "channel" + " is already closed due to previous "));
+              composeMessagePrefix(sse),
+              ((cause == null) ? sse.getCause() : cause));
+    }
+
+    private static String composeMessagePrefix(ShutdownSignalException sse) {
+        String connectionOrChannel = sse.isHardError() ? "connection " : "channel ";
+        return connectionOrChannel + "is already closed due to ";
     }
 }

src/com/rabbitmq/client/ShutdownSignalException.java

@@ -57,7 +57,7 @@ public ShutdownSignalException(boolean hardError,
                                    boolean initiatedByApplication,
                                    Method reason, Object ref)
     {
-        this(hardError, initiatedByApplication, reason, ref, "");
+        this(hardError, initiatedByApplication, reason, ref, "", null);
     }
 
     /**
@@ -70,19 +70,33 @@ public ShutdownSignalException(boolean hardError,
      */
     public ShutdownSignalException(boolean hardError,
                                    boolean initiatedByApplication,
-                                   Method reason, Object ref, String messagePrefix)
+                                   Method reason, Object ref, String messagePrefix, Throwable cause)
     {
-        super(messagePrefix + (initiatedByApplication
-                       ? ("clean " + (hardError ? "connection" : "channel") + " shutdown")
-                       : ((hardError ? "connection" : "channel") + " error"))
-                      + "; reason: " + reason);
+        super(composeMessage(hardError, initiatedByApplication, reason, messagePrefix, cause));
         this._hardError = hardError;
         this._initiatedByApplication = initiatedByApplication;
         this._reason = reason;
         // Depending on hardError what we got is either Connection or Channel reference
         this._ref = ref;
     }
 
+    private static String composeMessage(boolean hardError, boolean initiatedByApplication,
+                                         Method reason, String messagePrefix, Throwable cause) {
+        final String connectionOrChannel = hardError ? "connection" : "channel";
+        final String appInitiated = "clean " + connectionOrChannel + " shutdown";
+        final String nonAppInitiated = connectionOrChannel + " error";
+        final String explanation = initiatedByApplication ? appInitiated : nonAppInitiated;
+
+        StringBuilder result = new StringBuilder(messagePrefix).append(explanation);
+        if(reason != null) {
+            result.append("; protocol method: ").append(reason);
+        }
+        if(cause != null) {
+            result.append("; cause: ").append(cause);
+        }
+        return result.toString();
+    }
+
     /** @return true if this signals a connection error, or false if a channel error */
     public boolean isHardError() { return _hardError; }
 

src/com/rabbitmq/client/impl/AMQConnection.java

@@ -717,7 +717,7 @@ private ShutdownSignalException startShutdown(Method reason,
         sse.initCause(cause);
         if (!setShutdownCauseIfOpen(sse)) {
             if (initiatedByApplication)
-                throw new AlreadyClosedException(getCloseReason());
+                throw new AlreadyClosedException(getCloseReason(), cause);
         }
 
         // stop any heartbeating

test/src/com/rabbitmq/client/test/functional/ExceptionMessages.java

@@ -31,6 +31,7 @@ public void testAlreadyClosedExceptionMessageWithCleanClose() throws IOException
             channel.close();
             channel.queueDeclare(uuid, false, false, false, null);
         } catch (AlreadyClosedException ace) {
+            System.out.println(ace.getMessage());
             assertTrue(ace.getMessage().startsWith("channel is already closed due to clean channel shutdown"));
         }
     }