ongoing work on LOGBACK-1415

logback-classic/src/main/java/ch/qos/logback/classic/pattern/PrefixCompositeConverter.java

@@ -0,0 +1,39 @@
+package ch.qos.logback.classic.pattern;
+
+import static ch.qos.logback.core.util.OptionHelper.extractDefaultReplacement;
+
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.core.pattern.CompositeConverter;
+import ch.qos.logback.core.pattern.Converter;
+
+public class PrefixCompositeConverter extends CompositeConverter<ILoggingEvent> {
+
+    public String convert(ILoggingEvent event) {
+        StringBuilder buf = new StringBuilder();
+        Converter<ILoggingEvent> childConverter = this.getChildConverter();
+
+        for (Converter<ILoggingEvent> c = childConverter; c != null; c = c.getNext()) {
+            if (c instanceof MDCConverter) {
+                MDCConverter mdcConverter = (MDCConverter) c;
+
+                String firstOption = mdcConverter.getFirstOption();
+                String[] keyInfo = extractDefaultReplacement(firstOption);
+                String key = keyInfo[0];
+                if (key != null) {
+                    buf.append(key).append("=");
+                }
+            } else {
+
+            }
+            c.write(buf, event);
+        }
+        String intermediary = buf.toString();
+
+        return null;
+    }
+
+    protected String transform(ILoggingEvent event, String in) {
+        throw new UnsupportedOperationException();
+    }
+
+}