Composing Stream Messages

The session method createStreamMessage returns a new, empty stream message. You can then use the methods shown in Table 2–10 to write primitive data values into the message body, similarly to writing to a data stream: for example,

StreamMessage  outMsg = mySession.createStreamMessage();
outMsg.writeString("The Meaning of Life");
outMsg.writeInt(42);

As a convenience for handling values whose types are not known until execution time, the writeObject method accepts a string or an objectified primitive value of class Integer, Byte, Short, Long, Float, Double , Boolean, or Character and writes the corresponding string or primitive value to the message stream: for example, the statements

Integer  meaningOfLife = new Integer(42);
outMsg.writeObject(meaningOfLife);

are equivalent to

outMsg.writeInt(42);

This method will throw an exception (MessageFormatException) if the argument given to it is not of class String or one of the objectified primitive classes.

Once you’ve written the entire message contents to the stream, the reset method

outMsg.reset();

puts the message body in read-only mode and repositions the stream to the beginning, ready to read (see Processing Messages). When the message is in this state, any attempt to write to the message stream will throw the exception MessageNotWriteableException. A call to the clearBody method (inherited from the superinterface Message) deletes the entire message body and makes it writeable again.