Include JacksonJsonToObjectConverter, Spring Converter implementation to convert/map JSON to a POJO using Jackson's ObjectMapper.

Author: jxblum

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

@@ -0,0 +1,144 @@
+/*
+ * 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 com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.DeserializationFeature;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.MapperFeature;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.node.JsonNodeType;
+import com.fasterxml.jackson.databind.node.POJONode;
+
+import org.springframework.core.convert.converter.Converter;
+import org.springframework.dao.DataRetrievalFailureException;
+import org.springframework.data.mapping.MappingException;
+import org.springframework.geode.data.json.converter.JsonToObjectConverter;
+import org.springframework.geode.pdx.PdxInstanceWrapper;
+import org.springframework.lang.NonNull;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+import org.springframework.util.ClassUtils;
+import org.springframework.util.StringUtils;
+
+/**
+ * {@link JsonToObjectConverter} implementation using Jackson to convert {@link String JSON}
+ * to an {@link Object} (POJO).
+ *
+ * @author John Blum
+ * @see com.fasterxml.jackson.databind.JsonNode
+ * @see com.fasterxml.jackson.databind.ObjectMapper
+ * @see com.fasterxml.jackson.databind.node.POJONode
+ * @see org.springframework.core.convert.converter.Converter
+ * @see org.springframework.geode.data.json.converter.JsonToObjectConverter
+ * @since 1.3.0
+ */
+public class JacksonJsonToObjectConverter implements JsonToObjectConverter {
+
+	protected static final String AT_TYPE_FIELD_NAME = PdxInstanceWrapper.AT_TYPE_FIELD_NAME;
+
+	private ObjectMapper objectMapper = newObjectMapper();
+
+	/**
+	 * Constructs a new Jackson {@link ObjectMapper} to convert {@link String JSON} into an {@link Object} (POJO).
+	 *
+	 * @return a new Jackson {@link ObjectMapper}; never {@literal null}.
+	 * @see com.fasterxml.jackson.databind.ObjectMapper
+	 */
+	// TODO configure via an SPI
+	private @NonNull ObjectMapper newObjectMapper() {
+
+		return new ObjectMapper()
+			.configure(DeserializationFeature.FAIL_ON_IGNORED_PROPERTIES, false)
+			.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
+			.configure(MapperFeature.ACCEPT_CASE_INSENSITIVE_ENUMS, true)
+			.findAndRegisterModules();
+	}
+
+	/**
+	 * Returns a reference to the configured Jackson {@link ObjectMapper} used by this {@link Converter}
+	 * to convert {@link String JSON} into an {@link Object} (POJO).
+	 *
+	 * @return a reference to the configured Jackson {@link ObjectMapper}.
+	 */
+	protected @NonNull ObjectMapper getObjectMapper() {
+		return this.objectMapper;
+	}
+
+	/**
+	 * Converts from {@link String JSON} to an {@link Object} (POJO) using Jackson's {@link ObjectMapper}.
+	 *
+	 * @param json {@link String} containing {@literal JSON} to convert.
+	 * @return an {@link Object} (POJO) converted from the given {@link String JSON}.
+	 * @see #getObjectMapper()
+	 */
+	@Override
+	public @Nullable Object convert(@Nullable String json) {
+
+		if (StringUtils.hasText(json)) {
+
+			String objectTypeName = null;
+
+			try {
+
+				ObjectMapper objectMapper = getObjectMapper();
+
+				JsonNode jsonNode = objectMapper.readTree(json);
+
+				if (isPojo(jsonNode)) {
+					return ((POJONode) jsonNode).getPojo();
+				}
+				else {
+
+					Assert.state(jsonNode.isObject(), () -> String.format("The JSON [%s] must be an object", json));
+
+					Assert.state(jsonNode.has(AT_TYPE_FIELD_NAME),
+						() -> String.format("The JSON object [%1$s] must have an '%2$s' metadata field",
+							json, AT_TYPE_FIELD_NAME));
+
+					objectTypeName = jsonNode.get(AT_TYPE_FIELD_NAME).asText();
+
+					Class<?> objectType =
+						ClassUtils.forName(objectTypeName, Thread.currentThread().getContextClassLoader());
+
+					return objectMapper.readValue(json, objectType);
+				}
+			}
+			catch (ClassNotFoundException cause) {
+				throw new MappingException(String.format("Failed to map JSON [%1$s] to an Object of type [%2$s]",
+					json, objectTypeName), cause);
+			}
+			catch (JsonProcessingException cause) {
+				throw new DataRetrievalFailureException(String.format("Failed to read JSON [%s]", json), cause);
+			}
+		}
+
+		return null;
+	}
+
+	/**
+	 * Null-safe method to determine whether the given {@link JsonNode} represents a {@link Object POJO}.
+	 *
+	 * @param jsonNode {@link JsonNode} to evaluate.
+	 * @return a boolean value indicating whether the given {@link JsonNode} represents a {@link Object POJO}.
+	 * @see com.fasterxml.jackson.databind.JsonNode
+	 */
+	boolean isPojo(@Nullable JsonNode jsonNode) {
+
+		return jsonNode != null
+			&& (jsonNode instanceof POJONode || jsonNode.isPojo() || JsonNodeType.POJO.equals(jsonNode.getNodeType()));
+	}
+}