JDBC连接的获取： http://donald-draper.iteye.com/blog/2342011
Mysql负载均衡连接的获取： http://donald-draper.iteye.com/blog/2342089
Mysql主从复制读写分离连接的获取： http://donald-draper.iteye.com/blog/2342108
ConnectionImp创建MysqlIO ： http://donald-draper.iteye.com/blog/2342959
Mysql预编译SQL： http://donald-draper.iteye.com/blog/2342960
MysqlSQL PreparedStatement的查询: http://donald-draper.iteye.com/blog/2343083
MySQL ServerPreparedStatement查询： http://donald-draper.iteye.com/blog/2343124
前几篇文章中，我们谈到连接的获取，mysqlIO的初始化，今天来看一下SQL的预编译，从下面这一句开始：
PreparedStatement ps = con.prepareStatement("select count(*) from ?");
//ConnectionImpl
//获取sql的PreparedStatement
public PreparedStatement prepareStatement(String sql)
throws SQLException
{
//委托给prepareStatement(String sql, int resultSetType, int resultSetConcurrency)
return prepareStatement(sql, 1003, 1007);
}
//预编译PreparedStatement
public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency)
throws SQLException
{
//检查连接是否关闭，关闭则返回
checkClosed();
com.mysql.jdbc.PreparedStatement pStmt = null;
boolean canServerPrepare = true;//server是否可以预编译sql
String nativeSql = getProcessEscapeCodesForPrepStmts() ? nativeSQL(sql) : sql;
//判断server是否可以预编译sql
if(useServerPreparedStmts && getEmulateUnsupportedPstmts())
canServerPrepare = canHandleAsServerPreparedStatement(nativeSql);
//server可以预编译sql，且PreparedStatement为ServerPreparedStatement
if(useServerPreparedStmts && canServerPrepare)
{
//如果Server需要缓存PreparedStatement
if(getCachePreparedStatements())
//锁定server缓存， private LRUCache serverSideStatementCache;
synchronized(serverSideStatementCache)
{
//从缓存中移除sql对应的ServerPreparedStatement
pStmt = (ServerPreparedStatement)serverSideStatementCache.remove(sql);
if(pStmt != null)
{
((ServerPreparedStatement)pStmt).setClosed(false);
pStmt.clearParameters();
}
if(pStmt == null)
try
{
//如果缓存中不存在sql对应的ServerPreparedStatement，则创建
pStmt = ServerPreparedStatement.getInstance(this, nativeSql, database, resultSetType, resultSetConcurrency);
if(sql.length() < getPreparedStatementCacheSqlLimit())
((ServerPreparedStatement)pStmt).isCached = true;
//设置结果集类型
pStmt.setResultSetType(resultSetType);
//设置结果集并发策略
pStmt.setResultSetConcurrency(resultSetConcurrency);
}
catch(SQLException sqlEx)
{
if(getEmulateUnsupportedPstmts())
{
pStmt = (com.mysql.jdbc.PreparedStatement)clientPrepareStatement(nativeSql, resultSetType, resultSetConcurrency, false);
if(sql.length() < getPreparedStatementCacheSqlLimit())
serverSideStatementCheckCache.put(sql, Boolean.FALSE);
} else
{
throw sqlEx;
}
}
}
else
try
{ //如果Server不缓存PreparedStatement，则直接创建对应的ServerPreparedStatement
pStmt = ServerPreparedStatement.getInstance(this, nativeSql, database, resultSetType, resultSetConcurrency);
pStmt.setResultSetType(resultSetType);
pStmt.setResultSetConcurrency(resultSetConcurrency);
}
catch(SQLException sqlEx)
{
if(getEmulateUnsupportedPstmts())
pStmt = (com.mysql.jdbc.PreparedStatement)clientPrepareStatement(nativeSql, resultSetType, resultSetConcurrency, false);
else
throw sqlEx;
}
} else
{
//如果server不可以预编译sql，则创建sql对应的为clientPrepareStatement
pStmt = (com.mysql.jdbc.PreparedStatement)clientPrepareStatement(nativeSql, resultSetType, resultSetConcurrency, false);
}
return pStmt;
}
从上可以看出prepareStatement方法首先，检查连接是否关闭，关闭则直接返回；
根据server是否可以预编译sql和PreparedStatement是否为ServerPreparedStatement信息，
来确定返回的prepareStatement是ServerPreparedStatement还是com.mysql.jdbc.PreparedStatement，server可以预编译sql，且PreparedStatement为ServerPreparedStatement则返回的是ServerPreparedStatement，否则返回的是com.mysql.jdbc.PreparedStatement。
这里有两点要看，先看第一点ServerPreparedStatement，再看第二点clientPrepareStatement
1.
//如果缓存中不存在sql对应的ServerPreparedStatement，则创建
pStmt = ServerPreparedStatement.getInstance(this, nativeSql, database, resultSetType, resultSetConcurrency);
2.
//如果server不可以预编译sql，则创建sql对应的为clientPrepareStatement
pStmt = (com.mysql.jdbc.PreparedStatement)clientPrepareStatement(nativeSql, resultSetType, resultSetConcurrency, false);
//如果缓存中不存在sql对应的ServerPreparedStatement，则创建
pStmt = ServerPreparedStatement.getInstance(this, nativeSql, database, resultSetType, resultSetConcurrency);
public class ServerPreparedStatement extends com.mysql.jdbc.PreparedStatement
{
//JDBC4ServerPreparedStatement构造函数
private static final Constructor JDBC_4_SPS_CTOR;
protected static final int BLOB_STREAM_READ_BUF_SIZE = 8192;
private static final byte MAX_DATE_REP_LENGTH = 5;
private static final byte MAX_DATETIME_REP_LENGTH = 12;
private static final byte MAX_TIME_REP_LENGTH = 13;
private boolean hasOnDuplicateKeyUpdate;
private boolean detectedLongParameterSwitch;
private int fieldCount;
private boolean invalid;
private SQLException invalidationException;
private boolean isSelectQuery;//是否是select查询
private Buffer outByteBuffer;
private BindValue parameterBindings[];
private Field parameterFields[];//参数域
private Field resultFields[];//结果域
private boolean sendTypesToServer;
private long serverStatementId;
private int stringTypeCode;
private boolean serverNeedsResetBeforeEachExecution;
protected boolean isCached;
private boolean useAutoSlowLog;
private Calendar serverTzCalendar;
private Calendar defaultTzCalendar;
private boolean hasCheckedRewrite;
private boolean canRewrite;
private int locationOfOnDuplicateKeyUpdate;
static
{
if(Util.isJdbc4())
try
{
JDBC_4_SPS_CTOR = Class.forName("com.mysql.jdbc.JDBC4ServerPreparedStatement").getConstructor(new Class[] {
com.mysql.jdbc.ConnectionImpl.class, java.lang.String.class, java.lang.String.class, Integer.TYPE, Integer.TYPE
});
}
catch(SecurityException e)
{
throw new RuntimeException(e);
}
catch(NoSuchMethodException e)
{
throw new RuntimeException(e);
}
catch(ClassNotFoundException e)
{
throw new RuntimeException(e);
}
else
JDBC_4_SPS_CTOR = null;
}
//获取ServerPreparedStatement实例
protected static ServerPreparedStatement getInstance(ConnectionImpl conn, String sql, String catalog, int resultSetType, int resultSetConcurrency)
throws SQLException
{
if(!Util.isJdbc4())
return new ServerPreparedStatement(conn, sql, catalog, resultSetType, resultSetConcurrency);
return (ServerPreparedStatement)JDBC_4_SPS_CTOR.newInstance(new Object[] {
conn, sql, catalog, Constants.integerValueOf(resultSetType), Constants.integerValueOf(resultSetConcurrency)
});
IllegalArgumentException e;
e;
throw new SQLException(e.toString(), "S1000");
e;
throw new SQLException(e.toString(), "S1000");
e;
throw new SQLException(e.toString(), "S1000");
e;
Throwable target = e.getTargetException();
if(target instanceof SQLException)
throw (SQLException)target;
else
throw new SQLException(target.toString(), "S1000");
}
//ServerPreparedStatement构造函数
protected ServerPreparedStatement(ConnectionImpl conn, String sql, String catalog, int resultSetType, int resultSetConcurrency)
throws SQLException
{
super(conn, catalog);
hasOnDuplicateKeyUpdate = false;
detectedLongParameterSwitch = false;
invalid = false;
sendTypesToServer = false;
stringTypeCode = 254;
isCached = false;
hasCheckedRewrite = false;
canRewrite = false;
locationOfOnDuplicateKeyUpdate = -2;
checkNullOrEmptyQuery(sql);
hasOnDuplicateKeyUpdate = containsOnDuplicateKeyInString(sql);
int startOfStatement = findStartOfStatement(sql);
firstCharOfStmt = StringUtils.firstAlphaCharUc(sql, startOfStatement);
isSelectQuery = 'S' == firstCharOfStmt;
if(connection.versionMeetsMinimum(5, 0, 0))
serverNeedsResetBeforeEachExecution = !connection.versionMeetsMinimum(5, 0, 3);
else
serverNeedsResetBeforeEachExecution = !connection.versionMeetsMinimum(4, 1, 10);
useAutoSlowLog = connection.getAutoSlowLog();
useTrueBoolean = connection.versionMeetsMinimum(3, 21, 23);
hasLimitClause = StringUtils.indexOfIgnoreCase(sql, "LIMIT") != -1;
String statementComment = connection.getStatementComment();
originalSql = statementComment != null ? "/* " + statementComment + " */ " + sql : sql;
if(connection.versionMeetsMinimum(4, 1, 2))
stringTypeCode = 253;
else
stringTypeCode = 254;
try
{
//关键这里，预编译sql
serverPrepare(sql);
}
catch(SQLException sqlEx)
{
realClose(false, true);
throw sqlEx;
}
catch(Exception ex)
{
realClose(false, true);
SQLException sqlEx = SQLError.createSQLException(ex.toString(), "S1000", getExceptionInterceptor());
sqlEx.initCause(ex);
throw sqlEx;
}
setResultSetType(resultSetType);
setResultSetConcurrency(resultSetConcurrency);
parameterTypes = new int[parameterCount];
}
}
//预编译sql
private void serverPrepare(String sql)
throws SQLException
{
//获取connection的互斥锁
Object obj = connection.getMutex();
JVM INSTR monitorenter ;
MysqlIO mysql;
//获取 MysqlIO
mysql = connection.getIO();
if(connection.getAutoGenerateTestcaseScript())
dumpPrepareForTestcase();
try
{
long begin = 0L;
if(StringUtils.startsWithIgnoreCaseAndWs(sql, "LOAD DATA"))
isLoadDataQuery = true;
else
isLoadDataQuery = false;
if(connection.getProfileSql())
begin = System.currentTimeMillis();
String characterEncoding = null;
//获取connection编码信息
String connectionEncoding = connection.getEncoding();
if(!isLoadDataQuery && connection.getUseUnicode() && connectionEncoding != null)
characterEncoding = connectionEncoding;
//MysqlIO发送sql命令
Buffer prepareResultPacket = mysql.sendCommand(22, sql, null, false, characterEncoding, 0);
if(connection.versionMeetsMinimum(4, 1, 1))
prepareResultPacket.setPosition(1);
else
prepareResultPacket.setPosition(0);
serverStatementId = prepareResultPacket.readLong();
fieldCount = prepareResultPacket.readInt();
parameterCount = prepareResultPacket.readInt();
parameterBindings = new BindValue[parameterCount];
for(int i = 0; i < parameterCount; i++)
parameterBindings[i] = new BindValue();
connection.incrementNumberOfPrepares();
if(profileSQL)
eventSink.consumeEvent(new ProfilerEvent((byte)2, "", currentCatalog, connectionId, statementId, -1, System.currentTimeMillis(), mysql.getCurrentTimeNanosOrMillis() - begin, mysql.getQueryTimingUnits(), null, new Throwable(), truncateQueryToLog(sql)));
if(parameterCount > 0 && connection.versionMeetsMinimum(4, 1, 2) && !mysql.isVersion(5, 0, 0))
{
parameterFields = new Field[parameterCount];
Buffer metaDataPacket = mysql.readPacket();
for(int i = 0; !metaDataPacket.isLastDataPacket() && i < parameterCount; metaDataPacket = mysql.readPacket())
parameterFields[i++] = mysql.unpackField(metaDataPacket, false);
}
if(fieldCount > 0)
{
resultFields = new Field[fieldCount];
Buffer fieldPacket = mysql.readPacket();
for(int i = 0; !fieldPacket.isLastDataPacket() && i < fieldCount; fieldPacket = mysql.readPacket())
resultFields[i++] = mysql.unpackField(fieldPacket, false);
}
}
catch(SQLException sqlEx)
{
if(connection.getDumpQueriesOnException())
{
StringBuffer messageBuf = new StringBuffer(originalSql.length() + 32);
messageBuf.append("\n\nQuery being prepared when exception was thrown:\n\n");
messageBuf.append(originalSql);
sqlEx = ConnectionImpl.appendMessageToException(sqlEx, messageBuf.toString(), getExceptionInterceptor());
}
throw sqlEx;
}
connection.getIO().clearInputStream();
break MISSING_BLOCK_LABEL_557;
Exception exception;
exception;
connection.getIO().clearInputStream();
throw exception;
Exception exception1;
exception1;
throw exception1;
}
来看这一句:
//MysqlIO发送sql命令
Buffer prepareResultPacket = mysql.sendCommand(22, sql, null, false, characterEncoding, 0);
//MysqlIO
final Buffer sendCommand(int command, String extraData, Buffer queryPacket, boolean skipCheck, String extraDataCharEncoding, int timeoutMillis)
throws SQLException
{
commandCount++;
enablePacketDebug = connection.getEnablePacketDebug();
readPacketSequence = 0;
int oldTimeout = 0;
if(timeoutMillis != 0)
try
{
oldTimeout = mysqlConnection.getSoTimeout();
mysqlConnection.setSoTimeout(timeoutMillis);
}
catch(SocketException e)
{
throw SQLError.createCommunicationsException(connection, lastPacketSentTimeMs, lastPacketReceivedTimeMs, e, getExceptionInterceptor());
}
try
{
Buffer buffer;
try
{
checkForOutstandingStreamingData();
oldServerStatus = serverStatus;
serverStatus = 0;
hadWarnings = false;
warningCount = 0;
queryNoIndexUsed = false;
queryBadIndexUsed = false;
serverQueryWasSlow = false;
if(useCompression)
{
int bytesLeft = mysqlInput.available();
if(bytesLeft > 0)
mysqlInput.skip(bytesLeft);
}
try
{
clearInputStream();
if(queryPacket == null)
{
int packLength = 8 + (extraData == null ? 0 : extraData.length()) + 2;
if(sendPacket == null)
sendPacket = new Buffer(packLength);
packetSequence = -1;
readPacketSequence = 0;
checkPacketSequence = true;
sendPacket.clear();
sendPacket.writeByte((byte)command);
if(command == 2 || command == 5 || command == 6 || command == 3 || command == 22)
{
if(extraDataCharEncoding == null)
sendPacket.writeStringNoNull(extraData);
else
sendPacket.writeStringNoNull(extraData, extraDataCharEncoding, connection.getServerCharacterEncoding(), connection.parserKnowsUnicode(), connection);
} else
if(command == 12)
{
long id = Long.parseLong(extraData);
sendPacket.writeLong(id);
}
//发送sql Packet
send(sendPacket, sendPacket.getPosition());
} else
{
packetSequence = -1;
send(queryPacket, queryPacket.getPosition());
}
}
catch(SQLException sqlEx)
{
throw sqlEx;
}
catch(Exception ex)
{
throw SQLError.createCommunicationsException(connection, lastPacketSentTimeMs, lastPacketReceivedTimeMs, ex, getExceptionInterceptor());
}
Buffer returnPacket = null;
if(!skipCheck)
{
if(command == 23 || command == 26)
{
readPacketSequence = 0;
packetSequenceReset = true;
}
returnPacket = checkErrorPacket(command);
}
buffer = returnPacket;
}
catch(IOException ioEx)
{
throw SQLError.createCommunicationsException(connection, lastPacketSentTimeMs, lastPacketReceivedTimeMs, ioEx, getExceptionInterceptor());
}
return buffer;
}
finally
{
if(timeoutMillis != 0)
try
{
mysqlConnection.setSoTimeout(oldTimeout);
}
catch(SocketException e)
{
throw SQLError.createCommunicationsException(connection, lastPacketSentTimeMs, lastPacketReceivedTimeMs, e, getExceptionInterceptor());
}
}
}
//发送sql Packet
private final void sendSplitPackets(Buffer packet)
throws SQLException
{
try
{
Buffer headerPacket = splitBufRef != null ? (Buffer)splitBufRef.get() : null;
if(headerPacket == null)
{
headerPacket = new Buffer(maxThreeBytes + 4);
splitBufRef = new SoftReference(headerPacket);
}
int len = packet.getPosition();
int splitSize = maxThreeBytes;
int originalPacketPos = 4;
byte origPacketBytes[] = packet.getByteBuffer();
byte headerPacketBytes[] = headerPacket.getByteBuffer();
int packetLen;
for(; len >= maxThreeBytes; len -= splitSize)
{
packetSequence++;
headerPacket.setPosition(0);
headerPacket.writeLongInt(splitSize);
headerPacket.writeByte(packetSequence);
System.arraycopy(origPacketBytes, originalPacketPos, headerPacketBytes, 4, splitSize);
packetLen = splitSize + 4;
if(!useCompression)
{
mysqlOutput.write(headerPacketBytes, 0, splitSize + 4);
mysqlOutput.flush();
} else
{
headerPacket.setPosition(0);
Buffer packetToSend = compressPacket(headerPacket, 4, splitSize, 4);
packetLen = packetToSend.getPosition();
mysqlOutput.write(packetToSend.getByteBuffer(), 0, packetLen);
mysqlOutput.flush();
}
originalPacketPos += splitSize;
}
headerPacket.clear();
headerPacket.setPosition(0);
headerPacket.writeLongInt(len - 4);
packetSequence++;
headerPacket.writeByte(packetSequence);
if(len != 0)
System.arraycopy(origPacketBytes, originalPacketPos, headerPacketBytes, 4, len - 4);
packetLen = len - 4;
if(!useCompression)
{
//将数据包写入输出流
protected BufferedOutputStream mysqlOutput;
mysqlOutput.write(headerPacket.getByteBuffer(), 0, len);
mysqlOutput.flush();
} else
{
headerPacket.setPosition(0);
Buffer packetToSend = compressPacket(headerPacket, 4, packetLen, 4);
packetLen = packetToSend.getPosition();
mysqlOutput.write(packetToSend.getByteBuffer(), 0, packetLen);
mysqlOutput.flush();
}
}
catch(IOException ioEx)
{
throw SQLError.createCommunicationsException(connection, lastPacketSentTimeMs, lastPacketReceivedTimeMs, ioEx, getExceptionInterceptor());
}
}
从上面可以看出，ServerPreparedStatement实际上就是通过MysqlIO，将sql发送到Server端。
2.
//如果server不可以预编译sql，则创建sql对应的为clientPrepareStatement
pStmt = (com.mysql.jdbc.PreparedStatement)clientPrepareStatement(nativeSql, resultSetType, resultSetConcurrency, false);
protected PreparedStatement clientPrepareStatement(String sql, int resultSetType, int resultSetConcurrency, boolean processEscapeCodesIfNeeded)
throws SQLException
{
checkClosed();
String nativeSql = !processEscapeCodesIfNeeded || !getProcessEscapeCodesForPrepStmts() ? sql : nativeSQL(sql);
com.mysql.jdbc.PreparedStatement pStmt = null;
if(getCachePreparedStatements())
synchronized(cachedPreparedStatementParams)
{
//如果缓存，则从缓存中，获取对应的PreparedStatement.ParseInfo
PreparedStatement.ParseInfo pStmtInfo = (PreparedStatement.ParseInfo)cachedPreparedStatementParams.get(nativeSql);
if(pStmtInfo == null)
{
//如果缓存中，不存在ParseInfo，则创建PreparedStatement
pStmt = PreparedStatement.getInstance(this, nativeSql, database);
PreparedStatement.ParseInfo parseInfo = pStmt.getParseInfo();
if(parseInfo.statementLength < getPreparedStatementCacheSqlLimit())
{
if(cachedPreparedStatementParams.size() >= getPreparedStatementCacheSize())
{
Iterator oldestIter = cachedPreparedStatementParams.keySet().iterator();
long lruTime = 9223372036854775807L;
String oldestSql = null;
do
{
if(!oldestIter.hasNext())
break;
String sqlKey = (String)oldestIter.next();
PreparedStatement.ParseInfo lruInfo = (PreparedStatement.ParseInfo)cachedPreparedStatementParams.get(sqlKey);
if(lruInfo.lastUsed < lruTime)
{
lruTime = lruInfo.lastUsed;
oldestSql = sqlKey;
}
} while(true);
if(oldestSql != null)
cachedPreparedStatementParams.remove(oldestSql);
}
cachedPreparedStatementParams.put(nativeSql, pStmt.getParseInfo());
}
} else
{
pStmtInfo.lastUsed = System.currentTimeMillis();
pStmt = new com.mysql.jdbc.PreparedStatement(this, nativeSql, database, pStmtInfo);
}
}
else
pStmt = PreparedStatement.getInstance(this, nativeSql, database);
pStmt.setResultSetType(resultSetType);
pStmt.setResultSetConcurrency(resultSetConcurrency);
return pStmt;
}
总结：
prepareStatement方法首先，检查连接是否关闭，关闭则直接返回；
根据server是否可以预编译sql和PreparedStatement是否为ServerPreparedStatement信息，
来确定返回的prepareStatement是ServerPreparedStatement还是com.mysql.jdbc.PreparedStatement，server可以预编译sql，且PreparedStatement为ServerPreparedStatement则返回的是ServerPreparedStatement
否则返回的是com.mysql.jdbc.PreparedStatement。ServerPreparedStatement实际上就是通过MysqlIO，将sql发送到Server端。
//LRUCache,LRUCache实际上是一个Map
public class LRUCache extends LinkedHashMap
{
public LRUCache(int maxSize)
{
super(maxSize);
maxElements = maxSize;
}
//关键在这个方法，当Map，put或putAll时，当添加元素后，Map的size大于其maxSize，调用
//此方法，判断是否需要移除Eldest元素
protected boolean removeEldestEntry(java.util.Map.Entry eldest)
{
return size() > maxElements;
}
private static final long serialVersionUID = 1L;
protected int maxElements;
}
//MysqlIO
class MysqlIO
{
private static final int UTF8_CHARSET_INDEX = 33;
private static final String CODE_PAGE_1252 = "Cp1252";
protected static final int NULL_LENGTH = -1;
protected static final int COMP_HEADER_LENGTH = 3;
protected static final int MIN_COMPRESS_LEN = 50;
protected static final int HEADER_LENGTH = 4;
protected static final int AUTH_411_OVERHEAD = 33;
private static int maxBufferSize = 65535;
private static final int CLIENT_COMPRESS = 32;
protected static final int CLIENT_CONNECT_WITH_DB = 8;
private static final int CLIENT_FOUND_ROWS = 2;
private static final int CLIENT_LOCAL_FILES = 128;
private static final int CLIENT_LONG_FLAG = 4;
private static final int CLIENT_LONG_PASSWORD = 1;
private static final int CLIENT_PROTOCOL_41 = 512;
private static final int CLIENT_INTERACTIVE = 1024;
protected static final int CLIENT_SSL = 2048;
private static final int CLIENT_TRANSACTIONS = 8192;
protected static final int CLIENT_RESERVED = 16384;
protected static final int CLIENT_SECURE_CONNECTION = 32768;
private static final int CLIENT_MULTI_QUERIES = 65536;
private static final int CLIENT_MULTI_RESULTS = 131072;
private static final int SERVER_STATUS_IN_TRANS = 1;
private static final int SERVER_STATUS_AUTOCOMMIT = 2;
static final int SERVER_MORE_RESULTS_EXISTS = 8;
private static final int SERVER_QUERY_NO_GOOD_INDEX_USED = 16;
private static final int SERVER_QUERY_NO_INDEX_USED = 32;
private static final int SERVER_QUERY_WAS_SLOW = 2048;
private static final int SERVER_STATUS_CURSOR_EXISTS = 64;
private static final String FALSE_SCRAMBLE = "xxxxxxxx";
protected static final int MAX_QUERY_SIZE_TO_LOG = 1024;
protected static final int MAX_QUERY_SIZE_TO_EXPLAIN = 1048576;
protected static final int INITIAL_PACKET_SIZE = 1024;
private static String jvmPlatformCharset = null;
protected static final String ZERO_DATE_VALUE_MARKER = "0000-00-00";
protected static final String ZERO_DATETIME_VALUE_MARKER = "0000-00-00 00:00:00";
private static final int MAX_PACKET_DUMP_LENGTH = 1024;
private boolean packetSequenceReset;
protected int serverCharsetIndex;
private Buffer reusablePacket;
private Buffer sendPacket;
private Buffer sharedSendPacket;
protected BufferedOutputStream mysqlOutput;
protected ConnectionImpl connection;//Mysql connection
private Deflater deflater;
protected InputStream mysqlInput;//mysql输入流
private LinkedList packetDebugRingBuffer;
private RowData streamingData;
protected Socket mysqlConnection;//mysql socket
private SocketFactory socketFactory;// mysql socket的工场
private SoftReference loadFileBufRef;
private SoftReference splitBufRef;
protected String host;//host
protected String seed;
private String serverVersion;
private String socketFactoryClassName;
private byte packetHeaderBuf[];
private boolean colDecimalNeedsBump;
private boolean hadWarnings;
private boolean has41NewNewProt;
private boolean hasLongColumnInfo;
private boolean isInteractiveClient;
private boolean logSlowQueries;
private boolean platformDbCharsetMatches;
private boolean profileSql;
private boolean queryBadIndexUsed;
private boolean queryNoIndexUsed;
private boolean serverQueryWasSlow;
private boolean use41Extensions;
private boolean useCompression;
private boolean useNewLargePackets;
private boolean useNewUpdateCounts;
private byte packetSequence;
private byte readPacketSequence;
private boolean checkPacketSequence;
private byte protocolVersion;
private int maxAllowedPacket;
protected int maxThreeBytes;
protected int port;
protected int serverCapabilities;
private int serverMajorVersion;
private int serverMinorVersion;
private int oldServerStatus;
private int serverStatus;
private int serverSubMinorVersion;
private int warningCount;
protected long clientParam;
protected long lastPacketSentTimeMs;
protected long lastPacketReceivedTimeMs;
private boolean traceProtocol;
private boolean enablePacketDebug;
private Calendar sessionCalendar;
private boolean useConnectWithDb;
private boolean needToGrabQueryFromPacket;
private boolean autoGenerateTestcaseScript;
private long threadId;
private boolean useNanosForElapsedTime;
private long slowQueryThreshold;
private String queryTimingUnits;
private boolean useDirectRowUnpack;
private int useBufferRowSizeThreshold;
private int commandCount;
private List statementInterceptors;
private ExceptionInterceptor exceptionInterceptor;
private int statementExecutionDepth;
private boolean useAutoSlowLog;
static
{
OutputStreamWriter outWriter = null;
try
{
outWriter = new OutputStreamWriter(new ByteArrayOutputStream());
jvmPlatformCharset = outWriter.getEncoding();
}
finally
{
try
{
if(outWriter != null)
outWriter.close();
}
catch(IOException ioEx) { }
}
}
//MysqlIO构造
public MysqlIO(String host, int port, Properties props, String socketFactoryClassName, ConnectionImpl conn, int socketTimeout, int useBufferRowSizeThreshold)
throws IOException, SQLException
{
packetSequenceReset = false;
reusablePacket = null;
sendPacket = null;
sharedSendPacket = null;
mysqlOutput = null;
deflater = null;
mysqlInput = null;
packetDebugRingBuffer = null;
streamingData = null;
mysqlConnection = null;
socketFactory = null;
this.host = null;
serverVersion = null;
this.socketFactoryClassName = null;
packetHeaderBuf = new byte[4];
colDecimalNeedsBump = false;
hadWarnings = false;
has41NewNewProt = false;
hasLongColumnInfo = false;
isInteractiveClient = false;
logSlowQueries = false;
platformDbCharsetMatches = true;
profileSql = false;
queryBadIndexUsed = false;
queryNoIndexUsed = false;
serverQueryWasSlow = false;
use41Extensions = false;
useCompression = false;
useNewLargePackets = false;
useNewUpdateCounts = false;
packetSequence = 0;
readPacketSequence = -1;
checkPacketSequence = false;
protocolVersion = 0;
maxAllowedPacket = 1048576;
maxThreeBytes = 16581375;
this.port = 3306;
serverMajorVersion = 0;
serverMinorVersion = 0;
oldServerStatus = 0;
serverStatus = 0;
serverSubMinorVersion = 0;
warningCount = 0;
clientParam = 0L;
lastPacketSentTimeMs = 0L;
lastPacketReceivedTimeMs = 0L;
traceProtocol = false;
enablePacketDebug = false;
useDirectRowUnpack = true;
commandCount = 0;
statementExecutionDepth = 0;
connection = conn;
if(connection.getEnablePacketDebug())
packetDebugRingBuffer = new LinkedList();
traceProtocol = connection.getTraceProtocol();
useAutoSlowLog = connection.getAutoSlowLog();
this.useBufferRowSizeThreshold = useBufferRowSizeThreshold;
useDirectRowUnpack = connection.getUseDirectRowUnpack();
logSlowQueries = connection.getLogSlowQueries();
reusablePacket = new Buffer(1024);
sendPacket = new Buffer(1024);
this.port = port;
this.host = host;
this.socketFactoryClassName = socketFactoryClassName;
//创建socket的工场
socketFactory = createSocketFactory();
exceptionInterceptor = connection.getExceptionInterceptor();
try
{
//从socket的工场获取连接
mysqlConnection = socketFactory.connect(this.host, this.port, props);
if(socketTimeout != 0)
try
{
mysqlConnection.setSoTimeout(socketTimeout);
}
catch(Exception ex) { }
//握手
mysqlConnection = socketFactory.beforeHandshake();
if(connection.getUseReadAheadInput())
mysqlInput = new ReadAheadInputStream(mysqlConnection.getInputStream(), 16384, connection.getTraceProtocol(), connection.getLog());
else
if(connection.useUnbufferedInput())
//从mysqlConnection获取输入流
mysqlInput = mysqlConnection.getInputStream();
else
mysqlInput = new BufferedInputStream(mysqlConnection.getInputStream(), 16384);
//初始化mysqlOutput输出流
mysqlOutput = new BufferedOutputStream(mysqlConnection.getOutputStream(), 16384);
isInteractiveClient = connection.getInteractiveClient();
profileSql = connection.getProfileSql();
sessionCalendar = Calendar.getInstance();
autoGenerateTestcaseScript = connection.getAutoGenerateTestcaseScript();
needToGrabQueryFromPacket = profileSql || logSlowQueries || autoGenerateTestcaseScript;
if(connection.getUseNanosForElapsedTime() && Util.nanoTimeAvailable())
{
useNanosForElapsedTime = true;
queryTimingUnits = Messages.getString("Nanoseconds");
} else
{
queryTimingUnits = Messages.getString("Milliseconds");
}
if(connection.getLogSlowQueries())
calculateSlowQueryThreshold();
}
catch(IOException ioEx)
{
throw SQLError.createCommunicationsException(connection, 0L, 0L, ioEx, getExceptionInterceptor());
}
}
}