diff --git a/lib/hs/src/Thrift.hs b/lib/hs/src/Thrift.hs
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+--
+-- 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.
+--
+
+module Thrift
+    ( module Thrift.Transport
+    , module Thrift.Protocol
+    , AppExnType(..)
+    , AppExn(..)
+    , readAppExn
+    , writeAppExn
+    , ThriftException(..)
+    ) where
+
+import Control.Monad ( when )
+import Control.Exception
+
+import Data.Typeable ( Typeable )
+
+import Thrift.Transport
+import Thrift.Protocol
+
+
+data ThriftException = ThriftException
+  deriving ( Show, Typeable )
+instance Exception ThriftException
+
+data AppExnType
+    = AE_UNKNOWN
+    | AE_UNKNOWN_METHOD
+    | AE_INVALID_MESSAGE_TYPE
+    | AE_WRONG_METHOD_NAME
+    | AE_BAD_SEQUENCE_ID
+    | AE_MISSING_RESULT
+      deriving ( Eq, Show, Typeable )
+
+instance Enum AppExnType where
+    toEnum 0 = AE_UNKNOWN
+    toEnum 1 = AE_UNKNOWN_METHOD
+    toEnum 2 = AE_INVALID_MESSAGE_TYPE
+    toEnum 3 = AE_WRONG_METHOD_NAME
+    toEnum 4 = AE_BAD_SEQUENCE_ID
+    toEnum 5 = AE_MISSING_RESULT
+
+    fromEnum AE_UNKNOWN = 0
+    fromEnum AE_UNKNOWN_METHOD = 1
+    fromEnum AE_INVALID_MESSAGE_TYPE = 2
+    fromEnum AE_WRONG_METHOD_NAME = 3
+    fromEnum AE_BAD_SEQUENCE_ID = 4
+    fromEnum AE_MISSING_RESULT = 5
+
+data AppExn = AppExn { ae_type :: AppExnType, ae_message :: String }
+  deriving ( Show, Typeable )
+instance Exception AppExn
+
+writeAppExn :: (Protocol p, Transport t) => p t -> AppExn -> IO ()
+writeAppExn pt ae = do
+    writeStructBegin pt "TApplicationException"
+
+    when (ae_message ae /= "") $ do
+        writeFieldBegin pt ("message", T_STRING , 1)
+        writeString pt (ae_message ae)
+        writeFieldEnd pt
+
+    writeFieldBegin pt ("type", T_I32, 2);
+    writeI32 pt (fromEnum (ae_type ae))
+    writeFieldEnd pt
+    writeFieldStop pt
+    writeStructEnd pt
+
+readAppExn :: (Protocol p, Transport t) => p t -> IO AppExn
+readAppExn pt = do
+    readStructBegin pt
+    rec <- readAppExnFields pt (AppExn {ae_type = undefined, ae_message = undefined})
+    readStructEnd pt
+    return rec
+
+readAppExnFields pt rec = do
+    (n, ft, id) <- readFieldBegin pt
+    if ft == T_STOP
+        then return rec
+        else case id of
+                 1 -> if ft == T_STRING then
+                          do s <- readString pt
+                             readAppExnFields pt rec{ae_message = s}
+                          else do skip pt ft
+                                  readAppExnFields pt rec
+                 2 -> if ft == T_I32 then
+                          do i <- readI32 pt
+                             readAppExnFields pt rec{ae_type = (toEnum  i)}
+                          else do skip pt ft
+                                  readAppExnFields pt rec
+                 _ -> do skip pt ft
+                         readFieldEnd pt
+                         readAppExnFields pt rec
+