Add JsonToPdxConverter interface implementation converting JSON to PDX backed by Apache Geode's o.a.g.pdx.JSONFormatter class and Jackson's ObjectMapper.

Resolves gh-67.

spring-geode/src/main/java/org/springframework/geode/data/json/converter/support/JacksonJsonToPdxConverter.java

@@ -0,0 +1,149 @@
+/*
+ * Copyright 2020 the original author or authors.
+ *
+ * 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
+ *
+ *     https://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.springframework.geode.data.json.converter.support;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.node.ArrayNode;
+import com.fasterxml.jackson.databind.node.JsonNodeType;
+import com.fasterxml.jackson.databind.node.ObjectNode;
+
+import org.apache.geode.pdx.PdxInstance;
+
+import org.springframework.dao.DataRetrievalFailureException;
+import org.springframework.data.gemfire.util.CollectionUtils;
+import org.springframework.geode.data.json.converter.JsonToPdxArrayConverter;
+import org.springframework.geode.data.json.converter.JsonToPdxConverter;
+import org.springframework.lang.NonNull;
+import org.springframework.lang.Nullable;
+
+/**
+ * The {@link JacksonJsonToPdxConverter} class is an implementation of the {@link JsonToPdxArrayConverter} that is
+ * capable of converting an array of {@literal JSON} objects into an array of {@link PdxInstance PdxInstances}.
+ *
+ * @author John Blum
+ * @see com.fasterxml.jackson.databind.JsonNode
+ * @see com.fasterxml.jackson.databind.ObjectMapper
+ * @see com.fasterxml.jackson.databind.node.ArrayNode
+ * @see com.fasterxml.jackson.databind.node.ObjectNode
+ * @see org.apache.geode.pdx.PdxInstance
+ * @see org.springframework.geode.data.json.converter.JsonToPdxArrayConverter
+ * @see org.springframework.geode.data.json.converter.JsonToPdxConverter
+ * @since 1.3.0
+ */
+public class JacksonJsonToPdxConverter implements JsonToPdxArrayConverter {
+
+	private JsonToPdxConverter converter = newJsonToPdxConverter();
+
+	private ObjectMapper objectMapper = newObjectMapper();
+
+	private @NonNull <T> Iterable<T> asIterable(@NonNull Iterator<T> iterator) {
+		return () -> iterator;
+	}
+
+	// TODO configure via an SPI
+	private JsonToPdxConverter newJsonToPdxConverter() {
+		return new JSONFormatterJsonToPdxConverter();
+	}
+
+	// TODO configure via an SPI
+	private ObjectMapper newObjectMapper() {
+		return new ObjectMapper();
+	}
+
+	/**
+	 * Returns a reference to the configured {@link JsonToPdxConverter} used to convert from a single object,
+	 * {@literal JSON} {@link String} to PDX (i.e. as a {@link PdxInstance}.
+	 *
+	 * @return a reference to the configured {@link JsonToPdxConverter}; never {@literal null}.
+	 * @see org.springframework.geode.data.json.converter.JsonToPdxConverter
+	 */
+	protected @NonNull JsonToPdxConverter getJsonToPdxConverter() {
+		return this.converter;
+	}
+
+	/**
+	 * Returns a reference to the configured Jackson {@link ObjectMapper}.
+	 *
+	 * @return a reference to the configured Jackson {@link ObjectMapper}; never {@literal null}.
+	 * @see com.fasterxml.jackson.databind.ObjectMapper
+	 */
+	protected @NonNull ObjectMapper getObjectMapper() {
+		return this.objectMapper;
+	}
+
+	/**
+	 * Converts the given {@link String JSON} containing multiple objects into an array of {@link PdxInstance} objects.
+	 *
+	 * @param json {@link String JSON} data to convert.
+	 * @return an array of {@link PdxInstance} objects from the given {@link String JSON}.
+	 * @throws IllegalStateException if the {@link String JSON} does not start with
+	 * either a JSON array or a JSON object.
+	 * @see org.apache.geode.pdx.PdxInstance
+	 */
+	@Nullable @Override
+	public PdxInstance[] convert(String json) {
+
+		try {
+			JsonNode jsonNode = getObjectMapper().readTree(json);
+
+			List<PdxInstance> pdxList = new ArrayList<>();
+
+			if (isArray(jsonNode)) {
+
+				ArrayNode arrayNode = (ArrayNode) jsonNode;
+
+				JsonToPdxConverter converter = getJsonToPdxConverter();
+
+				for (JsonNode object : asIterable(CollectionUtils.nullSafeIterator(arrayNode.elements()))) {
+					pdxList.add(converter.convert(object.toString()));
+				}
+			}
+			else if (isObject(jsonNode)) {
+
+				ObjectNode objectNode = (ObjectNode) jsonNode;
+
+				pdxList.add(getJsonToPdxConverter().convert(objectNode.toString()));
+			}
+			else {
+
+				String message = String.format("Unable to process JSON node of type [%s];"
+					+ " expected either an [%s] or an [%s]", jsonNode.getNodeType(),
+						JsonNodeType.OBJECT, JsonNodeType.ARRAY);
+
+				throw new IllegalStateException(message);
+			}
+
+			return pdxList.toArray(new PdxInstance[0]);
+		}
+		catch (JsonProcessingException cause) {
+			throw new DataRetrievalFailureException("Failed to read JSON content", cause);
+		}
+	}
+
+	private boolean isArray(@Nullable JsonNode node) {
+		return node != null && (node.isArray() || JsonNodeType.ARRAY.equals(node.getNodeType()));
+	}
+
+	private boolean isObject(@Nullable JsonNode node) {
+		return node != null && (node.isObject() || JsonNodeType.OBJECT.equals(node.getNodeType()));
+	}
+}