Use StringBuilder for stack trace (#181)

Author: eyalkoren

ecs-logging-core/src/main/java/co/elastic/logging/EcsJsonSerializer.java

@@ -220,10 +220,6 @@ public static void serializeException(StringBuilder builder, Throwable thrown, b
         }
     }
 
-    public static void serializeException(StringBuilder builder, String exceptionClassName, String exceptionMessage, String stackTrace, boolean stackTraceAsArray) {
-        serializeException(builder, exceptionClassName, exceptionMessage, (CharSequence) stackTrace, stackTraceAsArray);
-    }
-
     public static void serializeException(StringBuilder builder, String exceptionClassName, CharSequence exceptionMessage, CharSequence stackTrace, boolean stackTraceAsArray) {
         builder.append("\"error.type\":\"");
         JsonUtils.quoteAsString(exceptionClassName, builder);

log4j2-ecs-layout/src/main/java/co/elastic/logging/log4j2/EcsLayout.java

@@ -341,9 +341,8 @@ private void serializeException(StringBuilder messageBuffer, LogEvent event) {
         Throwable thrown = event.getThrown();
         if (thrown != null) {
             if (exceptionPatternFormatter != null) {
-                StringBuilder builder = EcsJsonSerializer.getMessageStringBuilder();
-                formatPattern(event, exceptionPatternFormatter, builder);
-                String stackTrace = builder.toString();
+                StringBuilder stackTrace = EcsJsonSerializer.getMessageStringBuilder();
+                formatPattern(event, exceptionPatternFormatter, stackTrace);
                 EcsJsonSerializer.serializeException(messageBuffer, thrown.getClass().getName(), thrown.getMessage(), stackTrace, stackTraceAsArray);
             } else {
                 EcsJsonSerializer.serializeException(messageBuffer, thrown, stackTraceAsArray);