/**
* Return the underlying {@code MessageHeaders} instance.
*
* <p>Unless {@link #setLeaveMutable(boolean)} was set to {@code true}, after this call, the
* headers are immutable and this accessor can no longer modify them.
*
* <p>This method always returns the same {@code MessageHeaders} instance if invoked multiples
* times. To obtain a copy of the underlying headers, use {@link #toMessageHeaders()} or {@link
* #toMap()} instead.
*
* @since 4.1
*/
public MessageHeaders getMessageHeaders() {
if (!this.leaveMutable) {
setImmutable();
}
return this.headers;
}
