A standard Java logging filter that consolidates repeat messages up to a

specified count and reports "Previous message repeated N times." when a
non-duplicate message is finally logged.


git-svn-id: https://samskivert.googlecode.com/svn/trunk@1753 6335cc39-0255-0410-8fd6-9bcaacd3b74c

projects/samskivert/src/java/com/samskivert/util/RepeatRecordFilter.java

@@ -0,0 +1,77 @@
+//
+// samskivert library - useful routines for java programs
+// Copyright (C) 2001-2004 Michael Bayne
+// 
+// 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.util;
+
+import java.util.logging.Filter;
+import java.util.logging.Handler;
+import java.util.logging.LogManager;
+import java.util.logging.LogRecord;
+import java.util.logging.Logger;
+
+/**
+ * Filters repeated log messages, emitting "Previous message repeated N times."
+ * when a non-repeated message is eventually logged. Log record equality is
+ * determined by comparing the record's logging level, message text and stack
+ * trace (if provided).
+ */
+public class RepeatRecordFilter
+    implements Filter
+{
+    /**
+     * Configures the default logging handlers to use an instance of this
+     * filter.
+     */
+    public static void configureDefaultHandler (int maxRepeat)
+    {
+        Logger logger = LogManager.getLogManager().getLogger("");
+        Handler[] handlers = logger.getHandlers();
+        RepeatRecordFilter filter = new RepeatRecordFilter(maxRepeat);
+        for (int ii = 0; ii < handlers.length; ii++) {
+            handlers[ii].setFilter(filter);
+        }
+    }
+
+    public RepeatRecordFilter (int maxRepeat)
+    {
+        _maxCount = maxRepeat;
+    }
+
+    public boolean isLoggable (LogRecord record)
+    {
+        if (_previous != null && _count < _maxCount &&
+            record.getLevel() == _previous.getLevel() &&
+            ObjectUtil.equals(record.getMessage(), _previous.getMessage()) &&
+            ObjectUtil.equals(record.getThrown(), _previous.getThrown())) {
+            _count++;
+            return false;
+        }
+        if (_count > 0) {
+            // we have to do things in this order because we're going to recurse
+            String msg = "Previous message repeated " + _count + " times.";
+            _count = 0;
+            LogManager.getLogManager().getLogger(record.getLoggerName()).log(
+                _previous.getLevel(), msg);
+        }
+        _previous = record;
+        return true;
+    }
+
+    protected int _maxCount, _count;
+    protected LogRecord _previous;
+}