add explicit exception for unsupported encodings

git-svn-id: https://svn.code.sf.net/p/jackcess/code/jackcess/trunk@617 f203690c-595d-4dc9-a70b-905162fa7fd2

src/java/com/healthmarketscience/jackcess/DefaultCodecProvider.java

@@ -99,21 +99,21 @@ public class DefaultCodecProvider implements CodecProvider
 
   /**
    * CodecHandler implementation which always throws
-   * UnsupportedOperationException, useful for databases with unsupported
+   * UnsupportedCodecException, useful for databases with unsupported
    * encodings.
    */
   public static class UnsupportedHandler implements CodecHandler
   {
     public void decodePage(ByteBuffer page, int pageNumber) throws IOException
     {
-      throw new UnsupportedOperationException("Decoding not supported");
+      throw new UnsupportedCodecException("Decoding not supported.  Please choose a CodecProvider which supports reading the current database encoding.");
     }
 
     public ByteBuffer encodePage(ByteBuffer page, int pageNumber, 
                                  int pageOffset) 
       throws IOException
     {
-      throw new UnsupportedOperationException("Encoding not supported");
+      throw new UnsupportedCodecException("Encoding not supported.  Please choose a CodecProvider which supports writing the current database encoding.");
     }
   }
 

src/java/com/healthmarketscience/jackcess/UnsupportedCodecException.java

@@ -0,0 +1,48 @@
+/*
+Copyright (c) 2012 James Ahlborn
+
+This library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Lesser General Public
+License as published by the Free Software Foundation; either
+version 2.1 of the License, or (at your option) any later version.
+
+This library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public
+License along with this library; if not, write to the Free Software
+Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
+USA
+*/
+
+package com.healthmarketscience.jackcess;
+
+/**
+ * Exception thrown by a CodecHandler to indicate that the current encoding is
+ * not supported.  This generally indicates that a different CodecProvider
+ * needs to be chosen.
+ *
+ * @author James Ahlborn
+ */
+public class UnsupportedCodecException 
+  extends UnsupportedOperationException 
+{
+  private static final long serialVersionUID = 20120313L;  
+
+  public UnsupportedCodecException(String msg) 
+  {
+    super(msg);
+  }
+
+  public UnsupportedCodecException(String msg, Throwable t) 
+  {
+    super(msg, t);
+  }
+
+  public UnsupportedCodecException(Throwable t) 
+  {
+    super(t);
+  }
+}