Make additionalFields configurable for JUL (#118)

Author: felixbarny

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

@@ -25,6 +25,7 @@
 package co.elastic.logging;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 public class AdditionalField {
@@ -40,6 +41,9 @@ public AdditionalField(String key, String value) {
     }
 
     public static List<AdditionalField> parse(String additionalFields) {
+        if (additionalFields == null) {
+            return Collections.emptyList();
+        }
         String[] split = additionalFields.split(",");
         ArrayList<AdditionalField> result = new ArrayList<AdditionalField>(split.length);
         for (String additionalField : split) {

jul-ecs-formatter/src/main/java/co/elastic/logging/jul/EcsFormatter.java

@@ -54,6 +54,7 @@ public EcsFormatter() {
                 .getBoolean(getProperty("co.elastic.logging.jul.EcsFormatter.stackTraceAsArray", "false"));
         eventDataset = getProperty("co.elastic.logging.jul.EcsFormatter.eventDataset", null);
         eventDataset = EcsJsonSerializer.computeEventDataset(eventDataset, serviceName);
+        setAdditionalFields(getProperty("co.elastic.logging.jul.EcsFormatter.additionalFields", null));
     }
 
     @Override