Adding layout support to the logback ecs encoder (#220)

Signed-off-by: Difrango, Ronald <[email protected]>
Co-authored-by: dgempiuc <[email protected]>
Co-authored-by: eyalkoren <[email protected]>

logback-ecs-encoder/src/main/java/co/elastic/logging/logback/EcsEncoder.java

@@ -29,6 +29,7 @@
 import ch.qos.logback.classic.spi.ILoggingEvent;
 import ch.qos.logback.classic.spi.IThrowableProxy;
 import ch.qos.logback.classic.spi.ThrowableProxy;
+import ch.qos.logback.core.Layout;
 import ch.qos.logback.core.encoder.EncoderBase;
 import co.elastic.logging.AdditionalField;
 import co.elastic.logging.EcsJsonSerializer;
@@ -56,6 +57,7 @@ public class EcsEncoder extends EncoderBase<ILoggingEvent> {
     private boolean includeOrigin;
     private final List<AdditionalField> additionalFields = new ArrayList<AdditionalField>();
     private OutputStream os;
+    protected Layout<ILoggingEvent> messageLayout;
 
     @Override
     public byte[] headerBytes() {
@@ -105,7 +107,7 @@ public byte[] encode(ILoggingEvent event) {
         StringBuilder builder = new StringBuilder(256);
         EcsJsonSerializer.serializeObjectStart(builder, event.getTimeStamp());
         EcsJsonSerializer.serializeLogLevel(builder, event.getLevel().toString());
-        EcsJsonSerializer.serializeFormattedMessage(builder, event.getFormattedMessage());
+        serializeMessage(event, builder);
         EcsJsonSerializer.serializeEcsVersion(builder);
         serializeMarkers(event, builder);
         EcsJsonSerializer.serializeServiceName(builder, serviceName);
@@ -140,12 +142,21 @@ public byte[] encode(ILoggingEvent event) {
         return builder.toString().getBytes(UTF_8);
     }
 
+    private void serializeMessage(ILoggingEvent event, StringBuilder builder) {
+        if (messageLayout == null) {
+            EcsJsonSerializer.serializeFormattedMessage(builder, event.getFormattedMessage());
+        } else {
+            EcsJsonSerializer.serializeFormattedMessage(builder, messageLayout.doLayout(event));
+        }
+    }
+
     /**
      * Subclasses can override this to add custom fields.
      * The last character in the StringBuilder will be comma when this is called.
      * You must add a comma after each custom field.
      */
-    protected void addCustomFields(ILoggingEvent event, StringBuilder builder) {}
+    protected void addCustomFields(ILoggingEvent event, StringBuilder builder) {
+    }
 
     private void serializeMarkers(ILoggingEvent event, StringBuilder builder) {
         Marker marker = event.getMarker();
@@ -210,4 +221,13 @@ public void setEventDataset(String eventDataset) {
     public void setThrowableConverter(ThrowableHandlingConverter throwableConverter) {
         this.throwableConverter = throwableConverter;
     }
+
+    /**
+     * The supplied Layout will be applied specifically to format the <code>message</code> field based on the logging event.
+     *
+     * @param messageLayout
+     */
+    public void setMessageLayout(Layout<ILoggingEvent> messageLayout) {
+        this.messageLayout = messageLayout;
+    }
 }