Created a rule for checking file format version numbers.

git-svn-id: https://samskivert.googlecode.com/svn/trunk@456 6335cc39-0255-0410-8fd6-9bcaacd3b74c

projects/samskivert/src/java/com/samskivert/xml/CheckVersionRule.java

@@ -0,0 +1,67 @@
+//
+// $Id: CheckVersionRule.java,v 1.1 2001/11/17 03:55:35 mdb Exp $
+//
+// samskivert library - useful routines for java programs
+// Copyright (C) 2001 Walter Korman
+// 
+// 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.samskivert.xml;
+
+import org.apache.commons.digester.Digester;
+import org.apache.commons.digester.Rule;
+
+import com.samskivert.Log;
+
+/**
+ * Used to compare a file format version number in an XML file with the
+ * one compiled into the parsing code.
+ */
+public class CheckVersionRule extends Rule
+{
+    /**
+     * Constructs a check version rule with the specified know version
+     * number. If a version newer than the specified version is parsed, a
+     * big fat warning will be issued.
+     *
+     * @param version the version number that the compiled code expects to
+     * see.
+     * @param parserIdentifier the name of the parser using this rule
+     * which will be reported in the event of a version mismatch.
+     */
+    public CheckVersionRule (Digester digester, int version,
+                             String parserIdentifier)
+    {
+        super(digester);
+
+        // keep this for later
+        _version = version;
+        _parserIdentifier = parserIdentifier;
+    }
+
+    public void body (String bodyText)
+        throws Exception
+    {
+        int version = Integer.parseInt(bodyText.trim());
+        if (version > _version) {
+            Log.warning(_parserIdentifier + " only knows about version " +
+                        _version + ", but is being asked to parse a file " +
+                        "with version " + version + ". Wackiness may ensue.");
+        }
+    }
+
+    protected int _version;
+    protected String _parserIdentifier;
+}