1 files changed, 49 insertions, 0 deletions
diff --git a/qpid/java/client/src/main/java/org/apache/qpid/client/failover/FailoverException.java b/qpid/java/client/src/main/java/org/apache/qpid/client/failover/FailoverException.java
new file mode 100644
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+++ b/qpid/java/client/src/main/java/org/apache/qpid/client/failover/FailoverException.java
@@ -0,0 +1,49 @@
+/*
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.apache.qpid.client.failover;
+
+/**
+ * FailoverException is used to indicate that a synchronous request has failed to receive the reply that it is waiting
+ * for because the fail-over process has been started whilst it was waiting for its reply. Synchronous methods generally
+ * raise this exception to indicate that they must be re-tried once the fail-over process has completed.
+ *
+ * <p/><table id="crc"><caption>CRC Card</caption>
+ * <tr><th> Responsibilities <th> Collaborations
+ * <tr><td> Used to indicate failure of a synchronous request due to fail-over.
+ * </table>
+ *
+ * @todo This exception is created and passed as an argument to a method, rather than thrown. The exception is being
+ *       used to represent an event, passed out to other threads. Use of exceptions as arguments rather than as
+ *       exceptions is extremly confusing. Ideally use a condition or set a flag and check it instead.
+ *       This exceptions-as-events pattern seems to be in a similar style to Mina code, which is not pretty, but
+ *       potentially acceptable for that reason. We have the option of extending the mina model to add more events
+ *       to it, that is, anything that is interested in handling failover as an event occurs below the main
+ *       amq event handler, which knows the specific interface of the qpid handlers, which can pass this down as
+ *       an explicit event, without it being an exception. Add failover method to BlockingMethodFrameListener,
+ *       have it set a flag or interrupt the waiting thread, which then creates and raises this exception.
+ */
+public class FailoverException extends Exception
+{
+    public FailoverException(String message)
+    {
+        super(message);
+    }
+}