RocketMQ Consumer Serialize Only Support JSON ？

```java
public class DefaultRocketMQListenerContainer implements InitializingBean,
RocketMQListenerContainer, SmartLifecycle, ApplicationContextAware {
// ……

private Object doConvertMessage(MessageExt messageExt) {
if (Objects.equals(messageType, MessageExt.class) || Objects.equals(messageType, org.apache.rocketmq.common.message.Message.class)) {
return messageExt;
} else {
String str = new String(messageExt.getBody(), Charset.forName(charset));
if (Objects.equals(messageType, String.class)) {
return str;
} else {
// If msgType not string, use objectMapper change it.
try {
if (messageType instanceof Class) {
//if the messageType has not Generic Parameter
return this.getMessageConverter().fromMessage(MessageBuilder.withPayload(str).build(), (Class) messageType);
} else {
//if the messageType has Generic Parameter, then use SmartMessageConverter#fromMessage with third parameter "conversionHint".
//we have validate the MessageConverter is SmartMessageConverter in this#getMethodParameter.
return ((SmartMessageConverter) this.getMessageConverter()).fromMessage(MessageBuilder.withPayload(str).build(), (Class) ((ParameterizedType) messageType).getRawType(), methodParameter);
}
} catch (Exception e) {
log.info("convert failed. str:{}, msgType:{}", str, messageType);
throw new RuntimeException("cannot convert message to " + messageType, e);
}
}
}
}

// ……
}
```
这个直接就`new String()`了，后面`MessageConverter`发挥不出更大的作用，万一序列化用的是`hession`或者`kryo`就会失败。
顺便是否可以扩展一下不通的消费实例，不同的`RocketMQTemplate`设置不同的`MessageConverter`，来兼容很多公司的一些现状。

Start in DefaultRocketMQListenerContainer, especially doConvertMessage, and inspect how MessageConverter and RocketMQTemplate are currently configured. Determine how non-JSON or binary payload conversion and separate converters per consumer or template should be supported, then add focused coverage showing the intended conversion behavior.

Written by the indexing model from the issue text.