588 - [FEATURE] serialize requests to JSON

Signed-off-by: Jai2305 <jainjai2305@gmail.com>

CHANGELOG.md

@@ -12,6 +12,7 @@ This section is for maintaining a changelog for all breaking changes for the cli
 ### Added
 - Document HTTP/2 support ([#330](https://github.com/opensearch-project/opensearch-java/pull/330))
 - Add support for phase_took & search_pipeline request params ([#1036](https://github.com/opensearch-project/opensearch-java/pull/1036))
+- Add a serializer method for classes implementing JsonpSerializable.([#1064](https://github.com/opensearch-project/opensearch-java/pull/1064))
 
 ### Dependencies
 

java-client/src/main/java/org/opensearch/client/json/JsonpSerializable.java

@@ -33,11 +33,34 @@
 package org.opensearch.client.json;
 
 import jakarta.json.stream.JsonGenerator;
+import java.io.IOException;
+import java.io.StringWriter;
+import java.io.UncheckedIOException;
 
 /**
  * An object that is its own JsonP serializer
  */
 public interface JsonpSerializable {
 
     void serialize(JsonGenerator generator, JsonpMapper mapper);
+
+    /**
+     * A default method which returns string representation for the instances of classes
+     * implementing JsonpSerializable interface.<br>
+     * Usage : Eg for SearchRequest.class<pre>{@code SearchRequest implements JsonpSerializable{..}
+     * SearchRequest searchRequest = SearchRequest.of(request -> request...);
+     * String searchRequestString = searchRequest.writeValueAsString();}</pre>  <br>
+     *
+     */
+    default String toJsonString() {
+        try (StringWriter writer = new StringWriter()) {
+            try (JsonGenerator generator = JsonpUtils.DEFAULT_PROVIDER.createGenerator(writer)) {
+                serialize(generator, JsonpUtils.DEFAULT_JSONP_MAPPER);
+            }
+            return writer.toString();
+        } catch (IOException ex) {
+            throw new UncheckedIOException(ex);
+        }
+    }
+
 }

java-client/src/main/java/org/opensearch/client/json/JsonpUtils.java

@@ -32,9 +32,11 @@
 
 package org.opensearch.client.json;
 
+import jakarta.json.JsonException;
 import jakarta.json.JsonObject;
 import jakarta.json.JsonString;
 import jakarta.json.JsonValue;
+import jakarta.json.spi.JsonProvider;
 import jakarta.json.stream.JsonGenerator;
 import jakarta.json.stream.JsonLocation;
 import jakarta.json.stream.JsonParser;
@@ -59,6 +61,39 @@ public class JsonpUtils {
      *         JSON when advancing to next state.
      * @throws java.util.NoSuchElementException if there are no more parsing states.
      */
+
+    static final JsonProvider DEFAULT_PROVIDER = provider();
+
+    static JsonProvider provider() {
+        return JsonProvider.provider();
+    }
+
+    static final JsonpMapper DEFAULT_JSONP_MAPPER = new JsonpMapperBase() {
+        @Override
+        public JsonProvider jsonProvider() {
+            return DEFAULT_PROVIDER;
+        }
+
+        @Override
+        public <T> void serialize(T value, JsonGenerator generator) {
+            if (value instanceof JsonpSerializable) {
+                ((JsonpSerializable) value).serialize(generator, this);
+                return;
+            }
+
+            throw new JsonException(
+                "Cannot find a serializer for type " + value.getClass().getName() + ". Consider using a full-featured JsonpMapper"
+            );
+        }
+
+        @Override
+        protected <T> JsonpDeserializer<T> getDefaultDeserializer(Class<T> clazz) {
+            throw new JsonException(
+                "Cannot find a default deserializer for type " + clazz.getName() + ". Consider using a full-featured JsonpMapper"
+            );
+        }
+    };
+
     public static JsonParser.Event expectNextEvent(JsonParser parser, JsonParser.Event expected) {
         JsonParser.Event event = parser.next();
         expectEvent(parser, expected, event);

java-client/src/test/java/org/opensearch/client/opensearch/json/JsonpSerializableTest.java

@@ -0,0 +1,70 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.client.opensearch.json;
+
+import java.util.Collections;
+import org.junit.Assert;
+import org.junit.Test;
+import org.opensearch.client.opensearch._types.FieldValue;
+import org.opensearch.client.opensearch._types.Result;
+import org.opensearch.client.opensearch.core.IndexResponse;
+import org.opensearch.client.opensearch.core.SearchRequest;
+
+public class JsonpSerializableTest extends Assert {
+
+    // Test IndexResponse which extends WriteResponseBase which implements JsonpSerializable
+    @Test
+    public void testIndexResponse() {
+
+        String expectedStringValue =
+            "{\"_id\":\"id\",\"_index\":\"index\",\"_primary_term\":1,\"result\":\"created\",\"_seq_no\":2,\"_shards\":{\"failed\":1.0,\"successful\":1.0,\"total\":3.0,\"failures\":[{\"index\":\"index\",\"node\":\"node\",\"reason\":{\"type\":\"query_shard_exception\",\"reason\":\"Failed to create query.\"},\"shard\":1,\"status\":\"Failed\"}],\"skipped\":1.0},\"_version\":3}";
+        IndexResponse indexResponse = IndexResponse.of(
+            response -> response.result(Result.Created)
+                .index("index")
+                .id("id")
+                .primaryTerm(1)
+                .seqNo(2)
+                .version(3)
+                .shards(
+                    shardStats -> shardStats.total(3)
+                        .successful(1)
+                        .skipped(1)
+                        .failed(1)
+                        .failures(
+                            shardFailure -> shardFailure.index("index")
+                                .node("node")
+                                .shard(1)
+                                .status("Failed")
+                                .reason(cause -> cause.type("query_shard_exception").reason("Failed to create query."))
+                        )
+                )
+        );
+
+        String indexResponseString = indexResponse.toJsonString();
+        assertEquals(expectedStringValue, indexResponseString);
+    }
+
+    // Test SearchRequest which implements JsonpSerializable
+    @Test
+    public void testSearchResponse() {
+
+        String expectedStringValue =
+            "{\"aggregations\":{},\"query\":{\"match\":{\"name\":{\"query\":\"OpenSearch\"}}},\"terminate_after\":5}";
+        SearchRequest searchRequest = SearchRequest.of(
+            request -> request.index("index1", "index2")
+                .aggregations(Collections.emptyMap())
+                .terminateAfter(5L)
+                .query(q -> q.match(t -> t.field("name").query(FieldValue.of("OpenSearch"))))
+        );
+        String searchRequestString = searchRequest.toJsonString();
+        assertEquals(expectedStringValue, searchRequestString);
+
+    }
+
+}