Use SPI to provide named XContent parsers for ranking evaluation

modules/rank-eval/build.gradle

@@ -20,5 +20,6 @@
 esplugin {
   description 'The Rank Eval module adds APIs to evaluate ranking quality.'
   classname 'org.elasticsearch.index.rankeval.RankEvalPlugin'
+  hasClientJar = true
 }
 

modules/rank-eval/src/main/java/org/elasticsearch/index/rankeval/RankEvalNamedXContentProvider.java

@@ -0,0 +1,42 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you 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 org.elasticsearch.index.rankeval;
+
+import org.elasticsearch.common.ParseField;
+import org.elasticsearch.common.xcontent.NamedXContentRegistry;
+import org.elasticsearch.plugins.spi.NamedXContentProvider;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class RankEvalNamedXContentProvider implements NamedXContentProvider {
+
+    @Override
+    public List<NamedXContentRegistry.Entry> getNamedXContentParsers() {
+        List<NamedXContentRegistry.Entry> namedXContent = new ArrayList<>();
+        namedXContent.add(
+                new NamedXContentRegistry.Entry(EvaluationMetric.class, new ParseField(PrecisionAtK.NAME), PrecisionAtK::fromXContent));
+        namedXContent.add(new NamedXContentRegistry.Entry(EvaluationMetric.class, new ParseField(MeanReciprocalRank.NAME),
+                MeanReciprocalRank::fromXContent));
+        namedXContent.add(new NamedXContentRegistry.Entry(EvaluationMetric.class, new ParseField(DiscountedCumulativeGain.NAME),
+                DiscountedCumulativeGain::fromXContent));
+        return namedXContent;
+    }
+}

modules/rank-eval/src/main/java/org/elasticsearch/index/rankeval/RankEvalPlugin.java

@@ -23,13 +23,12 @@ import org.elasticsearch.action.ActionRequest;
 import org.elasticsearch.action.ActionResponse;
 import org.elasticsearch.cluster.metadata.IndexNameExpressionResolver;
 import org.elasticsearch.cluster.node.DiscoveryNodes;
-import org.elasticsearch.common.ParseField;
 import org.elasticsearch.common.io.stream.NamedWriteableRegistry;
 import org.elasticsearch.common.settings.ClusterSettings;
 import org.elasticsearch.common.settings.IndexScopedSettings;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.settings.SettingsFilter;
-import org.elasticsearch.common.xcontent.NamedXContentRegistry;
+import org.elasticsearch.common.xcontent.NamedXContentRegistry.Entry;
 import org.elasticsearch.plugins.ActionPlugin;
 import org.elasticsearch.plugins.Plugin;
 import org.elasticsearch.rest.RestController;
@@ -68,14 +67,7 @@ public class RankEvalPlugin extends Plugin implements ActionPlugin {
     }
 
     @Override
-    public List<NamedXContentRegistry.Entry> getNamedXContent() {
+    public List<Entry> getNamedXContent() {
-        List<NamedXContentRegistry.Entry> namedXContent = new ArrayList<>();
+        return new RankEvalNamedXContentProvider().getNamedXContentParsers();
-        namedXContent.add(
-                new NamedXContentRegistry.Entry(EvaluationMetric.class, new ParseField(PrecisionAtK.NAME), PrecisionAtK::fromXContent));
-        namedXContent.add(new NamedXContentRegistry.Entry(EvaluationMetric.class, new ParseField(MeanReciprocalRank.NAME),
-                MeanReciprocalRank::fromXContent));
-        namedXContent.add(new NamedXContentRegistry.Entry(EvaluationMetric.class, new ParseField(DiscountedCumulativeGain.NAME),
-                DiscountedCumulativeGain::fromXContent));
-        return namedXContent;
     }
 }

modules/rank-eval/src/main/resources/META-INF/services/org.elasticsearch.plugins.spi.NamedXContentProvider

@@ -0,0 +1 @@
+org.elasticsearch.index.rankeval.RankEvalNamedXContentProvider