Sending and Receiving Messages - TCP/IP Sockets in Java Practical Guide for Programmers - page 49

26

out.write('\n');

27

out.flush();

28

if (buf.size() > MAX_WIRE_LENGTH)

29

throw new IOException("Encoded length too long");

30

return buf.toByteArray();

31

}

32 }

ItemQuoteEncoderText.java

1. Constructors: lines 6-12
If no encoding is explicitly specified, we use the default encoding specified in the constant
interface.

2. encode() method: lines 14-31
Create an output buffer: lines 15-16
A ByteArrayOutputStream collects the bytes to be returned. Wrapping it in an Out−
putWriter allows us to take advantage of the latter's methods for converting strings
to bytes.
Write the first integer, followed by a space delimiter: line 17
Check for delimiter: lines 18-19
Make sure that the field delimiter is not contained in the field itself. If it is, throw an
exception.
Output itemDescription and other integers: lines 20-21
Write the flag characters if the booleans are true: lines 22-25
Write the delimiter for the flag field: line 26
Flush the output stream: lines 27-29
Flush everything to the underlying stream, and call size() to check that the resulting
byte sequence is not too long. The length restriction allows the receiver to know how
big a buffer is needed to receive into a DatagramPacket . (For stream communication,
this is not necessary, but it is still convenient.)
Return the byte array from the output stream: line 30

The decoding class ItemQuoteDecoderText simply inverts the encoding process.

ItemQuoteDecoderText.java

0 import java.io.*; // for InputStream, ByteArrayInputStream, and IOException
1 import java.net.*; // for DatagramPacket
2
3 public class ItemQuoteDecoderText implements ItemQuoteDecoder, ItemQuoteTextConst {
4
5

private String encoding; // Character encoding