Resolved issue #105: Added GelfLogRecord class which allows passing

src/main/java/org/graylog2/logging/GelfHandler.java

@@ -15,6 +15,7 @@
 import java.util.HashMap;
 import java.util.IllegalFormatConversionException;
 import java.util.Map;
+import java.util.Map.Entry;
 import java.util.logging.*;
 
 public class GelfHandler
@@ -215,6 +216,13 @@ private GelfMessage makeMessage(final LogRecord record) {
                         String.valueOf(levelToSyslogLevel(record.getLevel())));
         gelfMessage.addField("SourceClassName", record.getSourceClassName());
         gelfMessage.addField("SourceMethodName", record.getSourceMethodName());
+
+        if (record instanceof GelfLogRecord) {
+        	GelfLogRecord gelfLogRecord = (GelfLogRecord)record;
+        	for (Entry<String, Object> field : gelfLogRecord.getFields().entrySet()) {
+        		gelfMessage.addField(field.getKey(), field.getValue());
+        	}
+        }        
 
         if (null != getOriginHost()) {
             gelfMessage.setHost(getOriginHost());

src/main/java/org/graylog2/logging/GelfLogRecord.java

@@ -0,0 +1,34 @@
+package org.graylog2.logging;
+
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.logging.Level;
+import java.util.logging.LogRecord;
+
+public class GelfLogRecord extends LogRecord {
+	private static final long serialVersionUID = 43242341L;
+	private Map<String, Object> fields;
+
+	public GelfLogRecord(Level level, String msg) {
+		super(level, msg);
+	}
+
+	public void setField(String key, Object value) {
+		if (fields == null) {
+			fields = new LinkedHashMap<String, Object>();
+		}
+		fields.put(key, value);
+	}
+
+	public Object getField(String key) {
+		return fields != null ? fields.get(key) : null;
+	}
+
+	public Map<String, Object> getFields() {
+		if (fields == null) {
+			return Collections.emptyMap();
+		}
+		return Collections.unmodifiableMap(fields);
+	}
+}