ObjectStringMessageConverter.java

/*
 * Copyright 2017 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.cloud.stream.converter;

import java.nio.charset.Charset;

import org.springframework.messaging.Message;
import org.springframework.messaging.MessageHeaders;
import org.springframework.messaging.converter.AbstractMessageConverter;
import org.springframework.util.MimeType;

/**
 * A {@link org.springframework.messaging.converter.MessageConverter} to convert a
 * non-String objects to a String, when expected content type is "text/plain".
 * 
 * It only performs conversions to internal format and is a wrapper
 * around {@link Object#toString()}.
 * 
 * @author Marius Bogoevici
 *
 * @since 1.2
 */
public class ObjectStringMessageConverter extends AbstractMessageConverter {

	public ObjectStringMessageConverter() {
		super(new MimeType("text", "plain", Charset.forName("UTF-8")));
	}

	protected boolean supports(Class<?> clazz) {
		return true;
	}

	@Override
	protected boolean canConvertFrom(Message<?> message, Class<?> targetClass) {
		// only supports the conversion to String
		return supportsMimeType(message.getHeaders()) && String.class == targetClass;
	}

	protected Object convertFromInternal(Message<?> message, Class<?> targetClass, Object conversionHint) {
		if (message.getPayload() != null) {
			if (message.getPayload() instanceof byte[]) {
				return new String((byte[]) message.getPayload(), Charset.forName("UTF-8"));
			}
			else {
				return message.getPayload().toString();
			}
		}
		return null;
	}

	protected Object convertToInternal(Object payload, MessageHeaders headers, Object conversionHint) {
		if (payload != null) {
			if ((payload instanceof byte[])) {
				return new String((byte[]) payload, Charset.forName("UTF-8"));
			} else {
				return payload.toString();
			}
		}
		else {
			return null;
		}
	}

}