Use SPI in High Level Rest Client to load XContent parsers (#25098)

This commit adds a NamedXContentProvider interface that can 
be implemented by plugins or modules using Java's SPI feature 
in order to provide additional NamedXContent parsers to external
applications like the Java High Level Rest Client.

Author: tlrx

client/rest-high-level/src/main/java/org/elasticsearch/client/RestHighLevelClient.java

@@ -49,8 +49,7 @@
 import org.elasticsearch.common.xcontent.NamedXContentRegistry;
 import org.elasticsearch.common.xcontent.XContentParser;
 import org.elasticsearch.common.xcontent.XContentType;
-import org.elasticsearch.join.aggregations.ChildrenAggregationBuilder;
-import org.elasticsearch.join.aggregations.ParsedChildren;
+import org.elasticsearch.plugins.spi.NamedXContentProvider;
 import org.elasticsearch.rest.BytesRestResponse;
 import org.elasticsearch.rest.RestStatus;
 import org.elasticsearch.search.aggregations.Aggregation;
@@ -92,8 +91,6 @@
 import org.elasticsearch.search.aggregations.bucket.terms.ParsedLongTerms;
 import org.elasticsearch.search.aggregations.bucket.terms.ParsedStringTerms;
 import org.elasticsearch.search.aggregations.bucket.terms.StringTerms;
-import org.elasticsearch.search.aggregations.matrix.stats.MatrixStatsAggregationBuilder;
-import org.elasticsearch.search.aggregations.matrix.stats.ParsedMatrixStats;
 import org.elasticsearch.search.aggregations.metrics.avg.AvgAggregationBuilder;
 import org.elasticsearch.search.aggregations.metrics.avg.ParsedAvg;
 import org.elasticsearch.search.aggregations.metrics.cardinality.CardinalityAggregationBuilder;
@@ -142,11 +139,13 @@
 import org.elasticsearch.search.suggest.term.TermSuggestion;
 
 import java.io.IOException;
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.ServiceLoader;
 import java.util.Set;
 import java.util.function.Function;
 import java.util.stream.Collectors;
@@ -180,8 +179,9 @@ public RestHighLevelClient(RestClient restClient) {
      */
     protected RestHighLevelClient(RestClient restClient, List<NamedXContentRegistry.Entry> namedXContentEntries) {
         this.client = Objects.requireNonNull(restClient);
-        this.registry = new NamedXContentRegistry(Stream.of(getDefaultNamedXContents().stream(), namedXContentEntries.stream())
-                .flatMap(Function.identity()).collect(toList()));
+        this.registry = new NamedXContentRegistry(
+                Stream.of(getDefaultNamedXContents().stream(), getProvidedNamedXContents().stream(), namedXContentEntries.stream())
+                    .flatMap(Function.identity()).collect(toList()));
     }
 
     /**
@@ -566,8 +566,6 @@ static List<NamedXContentRegistry.Entry> getDefaultNamedXContents() {
         map.put(SignificantLongTerms.NAME, (p, c) -> ParsedSignificantLongTerms.fromXContent(p, (String) c));
         map.put(SignificantStringTerms.NAME, (p, c) -> ParsedSignificantStringTerms.fromXContent(p, (String) c));
         map.put(ScriptedMetricAggregationBuilder.NAME, (p, c) -> ParsedScriptedMetric.fromXContent(p, (String) c));
-        map.put(ChildrenAggregationBuilder.NAME, (p, c) -> ParsedChildren.fromXContent(p, (String) c));
-        map.put(MatrixStatsAggregationBuilder.NAME, (p, c) -> ParsedMatrixStats.fromXContent(p, (String) c));
         List<NamedXContentRegistry.Entry> entries = map.entrySet().stream()
                 .map(entry -> new NamedXContentRegistry.Entry(Aggregation.class, new ParseField(entry.getKey()), entry.getValue()))
                 .collect(Collectors.toList());
@@ -579,4 +577,15 @@ static List<NamedXContentRegistry.Entry> getDefaultNamedXContents() {
                 (parser, context) -> CompletionSuggestion.fromXContent(parser, (String)context)));
         return entries;
     }
+
+    /**
+     * Loads and returns the {@link NamedXContentRegistry.Entry} parsers provided by plugins.
+     */
+    static List<NamedXContentRegistry.Entry> getProvidedNamedXContents() {
+        List<NamedXContentRegistry.Entry> entries = new ArrayList<>();
+        for (NamedXContentProvider service : ServiceLoader.load(NamedXContentProvider.class)) {
+            entries.addAll(service.getNamedXContentParsers());
+        }
+        return entries;
+    }
 }

client/rest-high-level/src/test/java/org/elasticsearch/client/RestHighLevelClientTests.java

@@ -56,10 +56,12 @@
 import org.elasticsearch.common.xcontent.XContentParser;
 import org.elasticsearch.common.xcontent.cbor.CborXContent;
 import org.elasticsearch.common.xcontent.smile.SmileXContent;
+import org.elasticsearch.join.aggregations.ChildrenAggregationBuilder;
 import org.elasticsearch.rest.RestStatus;
 import org.elasticsearch.search.SearchHits;
 import org.elasticsearch.search.aggregations.Aggregation;
 import org.elasticsearch.search.aggregations.InternalAggregations;
+import org.elasticsearch.search.aggregations.matrix.stats.MatrixStatsAggregationBuilder;
 import org.elasticsearch.search.suggest.Suggest;
 import org.elasticsearch.test.ESTestCase;
 import org.junit.Before;
@@ -69,6 +71,7 @@
 
 import java.io.IOException;
 import java.net.SocketTimeoutException;
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
@@ -613,9 +616,9 @@ public void testWrapResponseListenerOnResponseExceptionWithIgnoresErrorValidBody
         assertEquals("Elasticsearch exception [type=exception, reason=test error message]", elasticsearchException.getMessage());
     }
 
-    public void testNamedXContents() {
+    public void testDefaultNamedXContents() {
         List<NamedXContentRegistry.Entry> namedXContents = RestHighLevelClient.getDefaultNamedXContents();
-        assertEquals(45, namedXContents.size());
+        assertEquals(43, namedXContents.size());
         Map<Class<?>, Integer> categories = new HashMap<>();
         for (NamedXContentRegistry.Entry namedXContent : namedXContents) {
             Integer counter = categories.putIfAbsent(namedXContent.categoryClass, 1);
@@ -624,10 +627,28 @@ public void testNamedXContents() {
             }
         }
         assertEquals(2, categories.size());
-        assertEquals(Integer.valueOf(42), categories.get(Aggregation.class));
+        assertEquals(Integer.valueOf(40), categories.get(Aggregation.class));
         assertEquals(Integer.valueOf(3), categories.get(Suggest.Suggestion.class));
     }
 
+    public void testProvidedNamedXContents() {
+        List<NamedXContentRegistry.Entry> namedXContents = RestHighLevelClient.getProvidedNamedXContents();
+        assertEquals(2, namedXContents.size());
+        Map<Class<?>, Integer> categories = new HashMap<>();
+        List<String> names = new ArrayList<>();
+        for (NamedXContentRegistry.Entry namedXContent : namedXContents) {
+            names.add(namedXContent.name.getPreferredName());
+            Integer counter = categories.putIfAbsent(namedXContent.categoryClass, 1);
+            if (counter != null) {
+                categories.put(namedXContent.categoryClass, counter + 1);
+            }
+        }
+        assertEquals(1, categories.size());
+        assertEquals(Integer.valueOf(2), categories.get(Aggregation.class));
+        assertTrue(names.contains(ChildrenAggregationBuilder.NAME));
+        assertTrue(names.contains(MatrixStatsAggregationBuilder.NAME));
+    }
+
     private static class TrackingActionListener implements ActionListener<Integer> {
         private final AtomicInteger statusCode = new AtomicInteger(-1);
         private final AtomicReference<Exception> exception = new AtomicReference<>();

core/src/main/java/org/elasticsearch/plugins/spi/NamedXContentProvider.java

@@ -0,0 +1,35 @@
+/*
+ * 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.plugins.spi;
+
+import org.elasticsearch.common.xcontent.NamedXContentRegistry;
+
+import java.util.List;
+
+/**
+ * Provides named XContent parsers.
+ */
+public interface NamedXContentProvider {
+
+    /**
+     * @return a list of {@link NamedXContentRegistry.Entry} that this plugin provides.
+     */
+    List<NamedXContentRegistry.Entry> getNamedXContentParsers();
+}

core/src/main/java/org/elasticsearch/plugins/spi/package-info.java

@@ -0,0 +1,25 @@
+/*
+ * 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.
+ */
+
+/**
+ * This package contains interfaces for services provided by
+ * Elasticsearch plugins to external applications like the
+ * Java High Level Rest Client.
+ */
+package org.elasticsearch.plugins.spi;

core/src/test/java/org/elasticsearch/plugins/spi/NamedXContentProviderTests.java

@@ -0,0 +1,81 @@
+/*
+ * 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.plugins.spi;
+
+import org.elasticsearch.common.ParseField;
+import org.elasticsearch.common.io.Streams;
+import org.elasticsearch.common.xcontent.NamedXContentRegistry;
+import org.elasticsearch.search.aggregations.Aggregation;
+import org.elasticsearch.search.aggregations.pipeline.ParsedSimpleValue;
+import org.elasticsearch.search.suggest.Suggest;
+import org.elasticsearch.search.suggest.term.TermSuggestion;
+import org.elasticsearch.test.ESTestCase;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.ServiceLoader;
+import java.util.function.Predicate;
+
+public class NamedXContentProviderTests extends ESTestCase {
+
+    public void testSpiFileExists() throws IOException {
+        String serviceFile = "/META-INF/services/" + NamedXContentProvider.class.getName();
+        List<String> implementations = new ArrayList<>();
+        try (InputStream input = NamedXContentProviderTests.class.getResourceAsStream(serviceFile)) {
+            Streams.readAllLines(input, implementations::add);
+        }
+
+        assertEquals(1, implementations.size());
+        assertEquals(TestNamedXContentProvider.class.getName(), implementations.get(0));
+    }
+
+    public void testNamedXContents() {
+        final List<NamedXContentRegistry.Entry> namedXContents = new ArrayList<>();
+        for (NamedXContentProvider service : ServiceLoader.load(NamedXContentProvider.class)) {
+            namedXContents.addAll(service.getNamedXContentParsers());
+        }
+
+        assertEquals(2, namedXContents.size());
+
+        List<Predicate<NamedXContentRegistry.Entry>> predicates = new ArrayList<>(2);
+        predicates.add(e -> Aggregation.class.equals(e.categoryClass) && "test_aggregation".equals(e.name.getPreferredName()));
+        predicates.add(e -> Suggest.Suggestion.class.equals(e.categoryClass) && "test_suggestion".equals(e.name.getPreferredName()));
+        predicates.forEach(predicate -> assertEquals(1, namedXContents.stream().filter(predicate).count()));
+    }
+
+    public static class TestNamedXContentProvider implements NamedXContentProvider {
+
+        public TestNamedXContentProvider() {
+        }
+
+        @Override
+        public List<NamedXContentRegistry.Entry> getNamedXContentParsers() {
+            return Arrays.asList(
+                    new NamedXContentRegistry.Entry(Aggregation.class, new ParseField("test_aggregation"),
+                            (parser, context) -> ParsedSimpleValue.fromXContent(parser, (String) context)),
+                    new NamedXContentRegistry.Entry(Suggest.Suggestion.class, new ParseField("test_suggestion"),
+                            (parser, context) -> TermSuggestion.fromXContent(parser, (String) context))
+            );
+        }
+    }
+}

core/src/test/resources/META-INF/services/org.elasticsearch.plugins.spi.NamedXContentProvider

@@ -0,0 +1 @@
+org.elasticsearch.plugins.spi.NamedXContentProviderTests$TestNamedXContentProvider

modules/aggs-matrix-stats/src/main/java/org/elasticsearch/search/aggregations/matrix/spi/MatrixStatsNamedXContentProvider.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.search.aggregations.matrix.spi;
+
+import org.elasticsearch.common.ParseField;
+import org.elasticsearch.common.xcontent.ContextParser;
+import org.elasticsearch.common.xcontent.NamedXContentRegistry;
+import org.elasticsearch.plugins.spi.NamedXContentProvider;
+import org.elasticsearch.search.aggregations.Aggregation;
+import org.elasticsearch.search.aggregations.matrix.stats.MatrixStatsAggregationBuilder;
+import org.elasticsearch.search.aggregations.matrix.stats.ParsedMatrixStats;
+
+import java.util.List;
+
+import static java.util.Collections.singletonList;
+
+public class MatrixStatsNamedXContentProvider implements NamedXContentProvider {
+
+    @Override
+    public List<NamedXContentRegistry.Entry> getNamedXContentParsers() {
+        ParseField parseField = new ParseField(MatrixStatsAggregationBuilder.NAME);
+        ContextParser<Object, Aggregation> contextParser = (p, name) -> ParsedMatrixStats.fromXContent(p, (String) name);
+        return singletonList(new NamedXContentRegistry.Entry(Aggregation.class, parseField, contextParser));
+    }
+}

modules/aggs-matrix-stats/src/main/resources/META-INF/services/org.elasticsearch.plugins.spi.NamedXContentProvider

@@ -0,0 +1 @@
+org.elasticsearch.search.aggregations.matrix.spi.MatrixStatsNamedXContentProvider

modules/parent-join/src/main/java/org/elasticsearch/join/spi/ParentJoinNamedXContentProvider.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.join.spi;
+
+import org.elasticsearch.common.ParseField;
+import org.elasticsearch.common.xcontent.ContextParser;
+import org.elasticsearch.common.xcontent.NamedXContentRegistry;
+import org.elasticsearch.join.aggregations.ChildrenAggregationBuilder;
+import org.elasticsearch.join.aggregations.ParsedChildren;
+import org.elasticsearch.plugins.spi.NamedXContentProvider;
+import org.elasticsearch.search.aggregations.Aggregation;
+
+import java.util.List;
+
+import static java.util.Collections.singletonList;
+
+public class ParentJoinNamedXContentProvider implements NamedXContentProvider {
+
+    @Override
+    public List<NamedXContentRegistry.Entry> getNamedXContentParsers() {
+        ParseField parseField = new ParseField(ChildrenAggregationBuilder.NAME);
+        ContextParser<Object, Aggregation> contextParser = (p, name) -> ParsedChildren.fromXContent(p, (String) name);
+        return singletonList(new NamedXContentRegistry.Entry(Aggregation.class, parseField, contextParser));
+    }
+}

modules/parent-join/src/main/resources/META-INF/services/org.elasticsearch.plugins.spi.NamedXContentProvider

@@ -0,0 +1 @@
+org.elasticsearch.join.spi.ParentJoinNamedXContentProvider