public abstract class CumulativeProtocolDecoder extends ProtocolDecoderAdapter
ProtocolDecoder that cumulates the content of received
buffers to a cumulative buffer to help users implement decoders.
If the received IoBuffer is only a part of a message.
decoders should cumulate received buffers to make a message complete or
to postpone decoding until more buffers arrive.
Here is an example decoder that decodes CRLF terminated lines into
Command objects:
public class CrLfTerminatedCommandLineDecoder
extends CumulativeProtocolDecoder {
private Command parseCommand(IoBuffer in) {
// Convert the bytes in the specified buffer to a
// Command object.
...
}
protected boolean doDecode(
IoSession session, IoBuffer in, ProtocolDecoderOutput out)
throws Exception {
// Remember the initial position.
int start = in.position();
// Now find the first CRLF in the buffer.
byte previous = 0;
while (in.hasRemaining()) {
byte current = in.get();
if (previous == '\r' && current == '\n') {
// Remember the current position and limit.
int position = in.position();
int limit = in.limit();
try {
in.position(start);
in.limit(position);
// The bytes between in.position() and in.limit()
// now contain a full CRLF terminated line.
out.write(parseCommand(in.slice()));
} finally {
// Set the position to point right after the
// detected line and set the limit to the old
// one.
in.position(position);
in.limit(limit);
}
// Decoded one line; CumulativeProtocolDecoder will
// call me again until I return false. So just
// return true until there are no more lines in the
// buffer.
return true;
}
previous = current;
}
// Could not find CRLF in the buffer. Reset the initial
// position to the one we recorded above.
in.position(start);
return false;
}
}
Please note that this decoder simply forward the call to
doDecode(IoSession, IoBuffer, ProtocolDecoderOutput) if the
underlying transport doesn't have a packet fragmentation. Whether the
transport has fragmentation or not is determined by querying
TransportMetadata.
| Modifier and Type | Field and Description |
|---|---|
private AttributeKey |
BUFFER |
| Modifier | Constructor and Description |
|---|---|
protected |
CumulativeProtocolDecoder()
Creates a new instance.
|
| Modifier and Type | Method and Description |
|---|---|
void |
decode(IoSession session,
IoBuffer in,
ProtocolDecoderOutput out)
Cumulates content of in into internal buffer and forwards
decoding request to
doDecode(IoSession, IoBuffer, ProtocolDecoderOutput). |
void |
dispose(IoSession session)
Releases the cumulative buffer used by the specified session.
|
protected abstract boolean |
doDecode(IoSession session,
IoBuffer in,
ProtocolDecoderOutput out)
Implement this method to consume the specified cumulative buffer and
decode its content into message(s).
|
private void |
removeSessionBuffer(IoSession session) |
private void |
storeRemainingInSession(IoBuffer buf,
IoSession session) |
finishDecodeprivate final AttributeKey BUFFER
protected CumulativeProtocolDecoder()
public void decode(IoSession session, IoBuffer in, ProtocolDecoderOutput out) throws java.lang.Exception
doDecode(IoSession, IoBuffer, ProtocolDecoderOutput).
doDecode() is invoked repeatedly until it returns false
and the cumulative buffer is compacted after decoding ends.java.lang.IllegalStateException - if your doDecode() returned
true not consuming the cumulative buffer.java.lang.Exception - if the read data violated protocol specificationprotected abstract boolean doDecode(IoSession session, IoBuffer in, ProtocolDecoderOutput out) throws java.lang.Exception
in - the cumulative bufferjava.lang.Exception - if cannot decode in.public void dispose(IoSession session) throws java.lang.Exception
dispose in interface ProtocolDecoderdispose in class ProtocolDecoderAdapterjava.lang.Exception - if failed to dispose all resourcesprivate void removeSessionBuffer(IoSession session)