RabbitMQ学习之messageconver插件实现(Gson)

RabbitMQ已经实现了Jackson的消息转换（Jackson2JsonMessageConverter），由于考虑到效率，如下使用Gson实现消息转换。

如下消息的转换类的接口MessageConverter，Jackson2JsonMessageConverter的父类AbstractJsonMessageConverter针对json转换的基类。

我们实现Gson2JsonMessageConverter转换类也继承AbstractJsonMessageConverter。

引入Gson的pom

			com.google.code.gson
			gson
			2.3
		

转换类实现如下：

package cn.slimsmart.rabbitmq.demo.spring.tag;

import java.io.IOException;
import java.io.UnsupportedEncodingException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.amqp.core.Message;
import org.springframework.amqp.core.MessageProperties;
import org.springframework.amqp.support.converter.AbstractJsonMessageConverter;
import org.springframework.amqp.support.converter.ClassMapper;
import org.springframework.amqp.support.converter.DefaultClassMapper;
import org.springframework.amqp.support.converter.MessageConversionException;

import com.google.gson.Gson;

public class Gson2JsonMessageConverter extends AbstractJsonMessageConverter {
	
	private static Log log = LogFactory.getLog(Gson2JsonMessageConverter.class);
	
	private static  ClassMapper classMapper =  new DefaultClassMapper();

	private static Gson gson = new Gson();

	public Gson2JsonMessageConverter() {
		super();
	}

	@Override
	protected Message createMessage(Object object,
			MessageProperties messageProperties) {
		byte[] bytes = null;
		try {
			String jsonString = gson.toJson(object);
			bytes = jsonString.getBytes(getDefaultCharset());
		}
		catch (IOException e) {
			throw new MessageConversionException(
					"Failed to convert Message content", e);
		}
		messageProperties.setContentType(MessageProperties.CONTENT_TYPE_JSON);
		messageProperties.setContentEncoding(getDefaultCharset());
		if (bytes != null) {
			messageProperties.setContentLength(bytes.length);
		}
		classMapper.fromClass(object.getClass(),messageProperties);
		return new Message(bytes, messageProperties);
	}

	@Override
	public Object fromMessage(Message message)
			throws MessageConversionException {
		Object content = null;
		MessageProperties properties = message.getMessageProperties();
		if (properties != null) {
			String contentType = properties.getContentType();
			if (contentType != null && contentType.contains("json")) {
				String encoding = properties.getContentEncoding();
				if (encoding == null) {
					encoding = getDefaultCharset();
				}
				try {
						Class targetClass = getClassMapper().toClass(
								message.getMessageProperties());
						content = convertBytesToObject(message.getBody(),
								encoding, targetClass);
				}
				catch (IOException e) {
					throw new MessageConversionException(
							"Failed to convert Message content", e);
				}
			}
			else {
				log.warn("Could not convert incoming message with content-type ["
						+ contentType + "]");
			}
		}
		if (content == null) {
			content = message.getBody();
		}
		return content;
	}

	private Object convertBytesToObject(byte[] body, String encoding,
			Class clazz) throws UnsupportedEncodingException {
		String contentAsString = new String(body, encoding);
		return gson.fromJson(contentAsString, clazz);
	}
}