最近看mysql提供的支持java语言的驱动包底层实现，我对于mysql不了解，所以现在卡在了驱动包在向mysql server调用rollback、commit以及其他的操作时候是如何被mysql server接受得到指令，当然具体指令我也不清楚，但是大概了解类似于oracle的undo回滚一样，我是这么想的！今天在iteye主要是询问以下问题？

1.mysql server如何接受client端的指令

2.比如rollback操作，指令长啥样？

3.mysql server接受指令后，后续操作实现(宽泛点亦可，讲深篇幅不够，兴许还看不懂)

以下我是在看mysql底层包所查到的相关代码

public QueryResult executeQuery(final Query dQuery) throws QueryException {

log.finest("Executing streamed query: " + dQuery);

this.hasMoreResults = false;

final StreamedQueryPacket packet = new StreamedQueryPacket(dQuery);

try {

// make sure we are in a good state

packetFetcher.clearInputStream();

packet.send(writer);

} catch (IOException e) {

throw new QueryException("Could not send query: " + e.getMessage(),

-1,

SQLExceptionMapper.SQLStates.CONNECTION_EXCEPTION.getSqlState(),

e);

}

final RawPacket rawPacket;

final ResultPacket resultPacket;

try {

rawPacket = packetFetcher.getRawPacket();

resultPacket = ResultPacketFactory.createResultPacket(rawPacket);

} catch (IOException e) {

throw new QueryException("Could not read resultset: " + e.getMessage(),

-1,

SQLExceptionMapper.SQLStates.CONNECTION_EXCEPTION.getSqlState(),

e);

}

switch (resultPacket.getResultType()) {

case ERROR:

final ErrorPacket ep = (ErrorPacket) resultPacket;

checkIfCancelled();

log.warning("Could not execute query " + dQuery + ": " + ((ErrorPacket) resultPacket).getMessage());

throw new QueryException(ep.getMessage(),

ep.getErrorNumber(),

ep.getSqlState());

case OK:

final OKPacket okpacket = (OKPacket) resultPacket;

this.hasMoreResults = okpacket.getServerStatus().contains(ServerStatus.MORE_RESULTS_EXISTS);

final QueryResult updateResult = new DrizzleUpdateResult(okpacket.getAffectedRows(),

okpacket.getWarnings(),

okpacket.getMessage(),

okpacket.getInsertId());

log.fine("OK, " + okpacket.getAffectedRows());

return updateResult;

case RESULTSET:

log.fine("SELECT executed, fetching result set");

try {

return this.createDrizzleQueryResult((ResultSetPacket) resultPacket);

} catch (IOException e) {

throw new QueryException("Could not read result set: " + e.getMessage(),

-1,

SQLExceptionMapper.SQLStates.CONNECTION_EXCEPTION.getSqlState(),

e);

}

default:

log.severe("Could not parse result..." + resultPacket.getResultType());

throw new QueryException("Could not parse result", (short) -1, SQLExceptionMapper.SQLStates.INTERRUPTED_EXCEPTION.getSqlState());

}

}

public int send(final OutputStream ostream) throws IOException,

QueryException

{

if (query.length() > MAX_PACKET_LENGTH - HEADER_LENGTH)

{

// Query can not be sent on only one network packet

return sendSplittedQuery(ostream);

}

else

{

byte[] byteHeader = Utils.copyWithLength(

intToByteArray( query.length() + 1), 5);

byteHeader[3] = (byte) 0;

byteHeader[4] = (byte) 0x03;

ostream.write(byteHeader);

query.writeTo(ostream);

ostream.flush();

return 0;

}

}

private int sendSplittedQuery(OutputStream ostream) throws QueryException,

IOException

{

int remainingBytes = query.length();

int offset = 0;

int packetIndex = 0;

while (remainingBytes >= 0L)

{

int packLength = Math.min(remainingBytes, MAX_PACKET_LENGTH);

byte[] byteHeader = null;

if (packetIndex == 0)

{

byteHeader = Utils.copyWithLength(intToByteArray(packLength), 5);

// Add the command byte

byteHeader[4] = (byte) 0x03;

// And remove 1 byte from available data length

packLength -= 1;

}

else

{

byteHeader = Utils.copyWithLength(intToByteArray(packLength), 4);

}

byteHeader[3] = (byte) packetIndex;

if(log.isLoggable(Level.FINEST)) {

log.finest("Sending packet " + packetIndex + " with length = "

+ packLength + " / " + remainingBytes);

}

ostream.write(byteHeader);

if(log.isLoggable(Level.FINEST)) {

log.finest("Header is " + MySQLProtocol.hexdump(byteHeader, 0));

}

if (packLength > 0)

{

query.writeTo(ostream, offset, packLength);

}

ostream.flush();

if (remainingBytes >= MAX_PACKET_LENGTH)

{

remainingBytes -= packLength;

offset += packLength;

packetIndex++;

}

else

remainingBytes = -1;

}

return packetIndex;

}

2014年4月23日 15:18