TupleToJsonStringConverter.java

/*
 * Copyright 2002-2015 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
 *
 * 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.springframework.xd.tuple;

import java.util.List;

import org.springframework.core.convert.converter.Converter;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ArrayNode;
import com.fasterxml.jackson.databind.node.BaseJsonNode;
import com.fasterxml.jackson.databind.node.ObjectNode;

/**
 * Converts a Tuple to JSON representation
 *
 * @author David Turanski
 * @author Gunnar Hillert
 *
 */
public class TupleToJsonStringConverter implements Converter<Tuple, String> {

	private final ObjectMapper mapper = new ObjectMapper();

	@Override
	public String convert(Tuple source) {
		ObjectNode root = toObjectNode(source);
		String json = null;
		try {
			json = mapper.writeValueAsString(root);
		}
		catch (Exception e) {
			throw new IllegalArgumentException("Tuple to string conversion failed", e);
		}
		return json;
	}

	private ObjectNode toObjectNode(Tuple source) {
		ObjectNode root = mapper.createObjectNode();
		for (int i = 0; i < source.size(); i++) {
			Object value = source.getValues().get(i);
			String name = source.getFieldNames().get(i);
			if (value == null) {
				root.putNull(name);
			} else {
				root.putPOJO(name, toNode(value));
			}
		}
		return root;
	}

	private ArrayNode toArrayNode(List<?> source) {
		ArrayNode array = mapper.createArrayNode();
		for (Object value : source) {
			if (value != null) {
				array.add(toNode(value));
			}
		}
		return array;
	}

	private BaseJsonNode toNode(Object value) {
		if (value != null) {
			if (value instanceof Tuple) {
				return toObjectNode((Tuple) value);
			}
			else if (value instanceof List<?>) {
				return toArrayNode((List<?>) value);
			}
			else if (!value.getClass().isPrimitive()) {
				return mapper.getNodeFactory().pojoNode(value);
			}
			else {
				return mapper.valueToTree(value);
			}
		}
		return null;
	}

}