Add a mixin for the MetricsRegistry serialization

components/common/src/main/java/com/hotels/styx/api/metrics/codahale/CodaHaleMetricRegistry.java

@@ -23,7 +23,6 @@
 import com.codahale.metrics.MetricFilter;
 import com.codahale.metrics.MetricRegistryListener;
 import com.codahale.metrics.Timer;
-import com.fasterxml.jackson.annotation.JsonValue;
 import com.hotels.styx.api.MetricRegistry;
 import com.hotels.styx.api.metrics.ScopedMetricRegistry;
 
@@ -55,7 +54,6 @@ public CodaHaleMetricRegistry() {
         this(new com.codahale.metrics.MetricRegistry());
     }
 
-    @JsonValue
     public com.codahale.metrics.MetricRegistry getMetricRegistry() {
         return metricRegistry;
     }

components/proxy/src/main/java/com/hotels/styx/admin/handlers/MetricsHandler.java

@@ -20,12 +20,15 @@
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.ObjectWriter;
+import com.fasterxml.jackson.databind.module.SimpleModule;
 import com.hotels.styx.api.FullHttpResponse;
 import com.hotels.styx.api.HttpInterceptor;
 import com.hotels.styx.api.HttpRequest;
 import com.hotels.styx.api.HttpResponse;
 import com.hotels.styx.api.MetricRegistry;
 import com.hotels.styx.api.StyxObservable;
+import com.hotels.styx.api.metrics.codahale.CodaHaleMetricRegistry;
+import com.hotels.styx.infrastructure.configuration.json.mixins.CodaHaleMetricRegistryMixin;
 
 import java.time.Duration;
 import java.util.Map;
@@ -53,7 +56,8 @@ public class MetricsHandler extends JsonHandler<MetricRegistry> {
     private static final String PRETTY_PRINT_PARAM = "pretty";
 
     private final ObjectMapper metricSerialiser = new ObjectMapper()
-            .registerModule(new MetricsModule(SECONDS, MILLISECONDS, DO_NOT_SHOW_SAMPLES));
+            .registerModule(new MetricsModule(SECONDS, MILLISECONDS, DO_NOT_SHOW_SAMPLES))
+            .addMixIn(CodaHaleMetricRegistry.class, CodaHaleMetricRegistryMixin.class);
 
     private final MetricRegistry metricRegistry;
 
@@ -64,11 +68,17 @@ public class MetricsHandler extends JsonHandler<MetricRegistry> {
      * @param cacheExpiration duration for which generated page content should be cached
      */
     public MetricsHandler(MetricRegistry metricRegistry, Optional<Duration> cacheExpiration) {
-        super(requireNonNull(metricRegistry), cacheExpiration, new MetricsModule(SECONDS, MILLISECONDS, DO_NOT_SHOW_SAMPLES));
+        super(requireNonNull(metricRegistry), cacheExpiration,
+            new MetricsModule(SECONDS, MILLISECONDS, DO_NOT_SHOW_SAMPLES),
+            new FullMetricsModule());
 
         this.metricRegistry = metricRegistry;
     }
-
+    private static class FullMetricsModule extends SimpleModule{
+        FullMetricsModule(){
+            setMixInAnnotation(CodaHaleMetricRegistry.class, CodaHaleMetricRegistryMixin.class);
+        }
+    }
     @Override
     public StyxObservable<HttpResponse> handle(HttpRequest request, HttpInterceptor.Context context) {
         MetricRequest metricRequest = new MetricRequest(request);

components/proxy/src/main/java/com/hotels/styx/infrastructure/configuration/json/mixins/CodaHaleMetricRegistryMixin.java

@@ -0,0 +1,28 @@
+/*
+  Copyright (C) 2013-2018 Expedia Inc.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+ */
+package com.hotels.styx.infrastructure.configuration.json.mixins;
+
+import com.fasterxml.jackson.annotation.JsonValue;
+
+/**
+ * Jackson annotations for {@link com.hotels.styx.api.metrics.codahale.CodaHaleMetricRegistry}.
+ */
+public abstract class CodaHaleMetricRegistryMixin {
+
+    @JsonValue
+    public abstract com.codahale.metrics.MetricRegistry getMetricRegistry();
+
+}