Create and open an ObjectOutput instance for the given output stream. This method should be used for opening data outputs when multiple objectToObjectStream() calls will be made before the stream is closed by calling finishObjectOutput().
This method also takes a boolean that represents whether this particular call to startObjectOutput() is reentrant or not. A call to startObjectOutput() should be marked reentrant whenever a 2nd or more calls to this method are made without having called finishObjectOutput() first.
To potentially speed up calling startObjectOutput multiple times in a non-reentrant way, i.e. startObjectOutput/finishObjectOutput...startObjectOutput/finishObjectOutput...etc, which is is the most common case, the StreamingMarshaller implementation could potentially use some mechanisms to speed up this startObjectOutput call.
On the other hand, when a call is reentrant, i.e. startObjectOutput/startObjectOutput(reentrant)...finishObjectOutput/finishObjectOutput, the StreamingMarshaller implementation might treat it differently. An example of reentrancy would be marshalling of {@link MarshalledValue}. When sending or storing a MarshalledValue, a call to startObjectOutput() would occur so that the stream is open and following, a 2nd call could occur so that MarshalledValue's raw byte array version is calculated and sent across. This enables storing as binary on the receiver side which is performance gain. The StreamingMarshaller implementation could decide that it needs a separate ObjectOutput or similar for the 2nd call since it's aim is only to get the raw byte array version and the close finish with it.
@param os output stream
@param isReentrant whether the call is reentrant or not.
@param estimatedSize estimated size in bytes of the output. Only meant as a possible performance optimization.
@return ObjectOutput to write to
@throws IOException