Reduce memory allocation when retrieving message content

DefaultMessage.getChannel is the method with the highest allocation rate in my application:

DefaultMessage creates defensive clones of the underlying byte[] for every invocation of getChannel and getBody:

public DefaultMessage(byte[] channel, byte[] body) {
   this.body = body;
   this.channel = channel;
}

public byte[] getChannel() {
   return channel.clone();
}

public byte[] getBody() {
   return body.clone();
}
 

I'm assuming this is done to ensure the message is immutable and that makes sense.

However, most invocations of getChannel do not actually need the underlying byte[]. Some are simple null checks and in the case of RedisIndexedSessionRepository, only the String value of the message is needed.

I suggest to add a couple of default methods to Message that directly use the underlying byte[] in the DefaultMessage implementation:

public boolean hasChannel() {
   return !ObjectUtils.isEmpty(channel);
}
 
public boolean hasBody() {
   return !ObjectUtils.isEmpty(body);
}

public String getChannelAsString() {
   return new String(channel);
}

public String getBodyAsString() { 
   return new String(channel); 
}

public ByteArrayWrapper wrapChannel() {
   return new ByteArrayWrapper(channel);
}

public ByteArrayWrapper wrapBody() {
 return new ByteArrayWrapper(body);
}

Nearly all allocations can be prevented by adding these methods while still maintaining immutability and - by using default methods in the Message interface - API compatibility.

I will create a PR for this.