JDBC连接的获取

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jdbc mysql

JDBC驱动初始化-Mysql:http://donald-draper.iteye.com/admin/blogs/2342010
MySQL读写分离又一好办法使用 com.mysql.jdbc.ReplicationDriver :
http://www.cnblogs.com/taven/archive/2013/04/24/3040489.html
Configuring Master/Slave Replication with Connector/J:
http://dev.mysql.com/doc/connector-j/5.1/en/connector-j-master-slave-replication-connection.html
JDBC访问Mysql进行读写分离测试：http://blog.csdn.net/hzw2312/article/details/9145307
Configuring Load Balancing with Connector/J:
http://dev.mysql.com/doc/connector-j/5.1/en/connector-j-usagenotes-j2ee-concepts-managing-load-balanced-connections.html
DatabaseMetaData：http://blog.csdn.net/anxinliu2011/article/details/7560511
上一篇，我们探究了一下驱动的初始化，今天，我们来看一下如何从驱动管理器获取连接。
下面来看如果从DriverManager获取连接：

 con = DriverManager.getConnection(url, user, password);

//DriverManager
//获取连接，将user和password放到Properties，将工作委托给

 public static Connection getConnection(String url, 
	String user, String password) throws SQLException {
        java.util.Properties info = new java.util.Properties();

        // Gets the classloader of the code that called this method, may 
	// be null.
	ClassLoader callerCL = DriverManager.getCallerClassLoader();

	if (user != null) {
	    info.put("user", user);
	}
	if (password != null) {
	    info.put("password", password);
	}

        return (getConnection(url, info, callerCL));
    }
    //获取类加载器
   /* Returns the caller's class loader, or null if none */
    private static native ClassLoader getCallerClassLoader();
    //连接的获取
    //  Worker method called by the public getConnection() methods.
    private static Connection getConnection(
	String url, java.util.Properties info, ClassLoader callerCL) throws SQLException {
	java.util.Vector drivers = null;
        /*
	 * When callerCl is null, we should check the application's
	 * (which is invoking this class indirectly)
	 * classloader, so that the JDBC driver class outside rt.jar
	 * can be loaded from here.
	 */
	synchronized(DriverManager.class) {	 
	  // synchronize loading of the correct classloader.
	  if(callerCL == null) {
	      callerCL = Thread.currentThread().getContextClassLoader();
	   }    
	} 
	 
	if(url == null) {
	    throw new SQLException("The url cannot be null", "08001");
	}
    
	println("DriverManager.getConnection(\"" + url + "\")");
        //如果没有初始化，先初始化，这部分，我们在上一篇，已经说过，这里不再赘述
	if (!initialized) {
	    initialize();
	}
        //copy readDrivers
	synchronized (DriverManager.class){ 
            // use the readcopy of drivers
	    drivers = readDrivers;  
        }

	// Walk through the loaded drivers attempting to make a connection.
	// Remember the first exception that gets raised so we can reraise it.
	SQLException reason = null;
	for (int i = 0; i < drivers.size(); i++) {
	    //从驱动集合类获取驱动
	    DriverInfo di = (DriverInfo)drivers.elementAt(i);
      
	    // If the caller does not have permission to load the driver then 
	    // skip it.
	    //获取合适的驱动
	    if ( getCallerClass(callerCL, di.driverClassName ) != di.driverClass ) {
		println("    skipping: " + di);
		continue;
	    }
	    try {
		println("    trying " + di);
		//从驱动获取Connection，关键在这里
		Connection result = di.driver.connect(url, info);
		if (result != null) {
		    // Success!
		    println("getConnection returning " + di);
		    return (result);
		}
	    } catch (SQLException ex) {
		if (reason == null) {
		    reason = ex;
		}
	    }
	}
    
	// if we got here nobody could connect.
	if (reason != null)    {
	    println("getConnection failed: " + reason);
	    throw reason;
	}
	println("getConnection: no suitable driver found for "+ url);
	throw new SQLException("No suitable driver found for "+ url, "08001");
    }

下面我们来看com.mysql.jdbc.Driver如何获取连接

public class Driver extends NonRegisteringDriver
    implements java.sql.Driver
{
    public Driver()
        throws SQLException
    {
    }
    static 
    {
        try
        {
            DriverManager.registerDriver(new Driver());
        }
        catch(SQLException E)
        {
            throw new RuntimeException("Can't register driver!");
        }
    }
}

查看NonRegisteringDriver
//NonRegisteringDriver

public class NonRegisteringDriver
    implements Driver
{
   //获取连接
 public Connection connect(String url, Properties info)
        throws SQLException
    {
        Properties props;
        if(url != null)
        {
	    //如果url以jdbc:mysql:loadbalance://则调用负载均衡连接获取方法
            if(StringUtils.startsWithIgnoreCase(url, "jdbc:mysql:loadbalance://"))
                return connectLoadBalanced(url, info);
	    //如果url以jdbc:mysql:replication://则调用集群连接获取方法
            if(StringUtils.startsWithIgnoreCase(url, "jdbc:mysql:replication://"))
                return connectReplicationConnection(url, info);
        }
        props = null;
	解析url
        if((props = parseURL(url, info)) == null)
            return null;
	//获取mysql连接
        com.mysql.jdbc.Connection newConn = ConnectionImpl.getInstance(host(props), port(props), props, database(props), url);
        return newConn;
        SQLException sqlEx;
        sqlEx;
        throw sqlEx;
        Exception ex;
        ex;
        SQLException sqlEx = SQLError.createSQLException(Messages.getString("NonRegisteringDriver.17") + ex.toString() + Messages.getString("NonRegisteringDriver.18"), "08001", null);
        sqlEx.initCause(ex);
        throw sqlEx;
    }

连接的获取这一部分有3个点我们分别来看：
1.
//如果url以jdbc:mysql:loadbalance://则调用负载均衡连接获取方法
if(StringUtils.startsWithIgnoreCase(url, "jdbc:mysql:loadbalance://"))
       return connectLoadBalanced(url, info);
2.
//如果url以jdbc:mysql:replication://则调用集群连接获取方法
if(StringUtils.startsWithIgnoreCase(url, "jdbc:mysql:replication://"))
                return connectReplicationConnection(url, info);
3.
//解析url
if((props = parseURL(url, info)) == null)
       return null;
//获取mysql连接
com.mysql.jdbc.Connection newConn = ConnectionImpl.getInstance(host(props), port(props), props, database(props), url);

我们先看获取单个Server的连接
//解析url

 public Properties parseURL(String url, Properties defaults)
        throws SQLException
    {
        Properties urlProps = defaults == null ? new Properties() : new Properties(defaults);
        if(url == null)
            return null;
	//如果url不以jdbc:mysql://开头，则返回
        if(!StringUtils.startsWithIgnoreCase(url, "jdbc:mysql://") && !StringUtils.startsWithIgnoreCase(url, "jdbc:mysql:mxj://") && !StringUtils.startsWithIgnoreCase(url, "jdbc:mysql:loadbalance://") && !StringUtils.startsWithIgnoreCase(url, "jdbc:mysql:replication://"))
            return null;
        int beginningOfSlashes = url.indexOf("//");
        if(StringUtils.startsWithIgnoreCase(url, "jdbc:mysql:mxj://"))
            urlProps.setProperty("socketFactory", "com.mysql.management.driverlaunched.ServerLauncherSocketFactory");
        int index = url.indexOf("?");
	//解析查询参数useUnicode=true&characterEncoding=utf8&characterSetResults=utf8
	//jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf8&characterSetResults=utf8
        if(index != -1)
        {
            String paramString = url.substring(index + 1, url.length());
            url = url.substring(0, index);
            StringTokenizer queryParams = new StringTokenizer(paramString, "&");
            do
            {
                if(!queryParams.hasMoreTokens())
                    break;
                String parameterValuePair = queryParams.nextToken();
                int indexOfEquals = StringUtils.indexOfIgnoreCase(0, parameterValuePair, "=");
                String parameter = null;
                String value = null;
                if(indexOfEquals != -1)
                {
                    parameter = parameterValuePair.substring(0, indexOfEquals);
                    if(indexOfEquals + 1 < parameterValuePair.length())
                        value = parameterValuePair.substring(indexOfEquals + 1);
                }
                if(value != null && value.length() > 0 && parameter != null && parameter.length() > 0)
                    try
                    {
                        urlProps.put(parameter, URLDecoder.decode(value, "UTF-8"));
                    }
                    catch(UnsupportedEncodingException badEncoding)
                    {
                        urlProps.put(parameter, URLDecoder.decode(value));
                    }
                    catch(NoSuchMethodError nsme)
                    {
                        urlProps.put(parameter, URLDecoder.decode(value));
                    }
            } while(true);
        }
        url = url.substring(beginningOfSlashes + 2);
        String hostStuff = null;
        int slashIndex = url.indexOf("/");
        if(slashIndex != -1)
        {
            hostStuff = url.substring(0, slashIndex);
            if(slashIndex + 1 < url.length())
	        //url中的db
                urlProps.put("DBNAME", url.substring(slashIndex + 1, url.length()));
        } else
        {
            hostStuff = url;
        }
        if(hostStuff != null && hostStuff.length() > 0)
	     //url中host
            urlProps.put("HOST", hostStuff);
        String propertiesTransformClassName = urlProps.getProperty("propertiesTransform");
        if(propertiesTransformClassName != null)
            try
            {
                ConnectionPropertiesTransform propTransformer = (ConnectionPropertiesTransform)Class.forName(propertiesTransformClassName).newInstance();
                urlProps = propTransformer.transformProperties(urlProps);
            }
            catch(InstantiationException e)
            {
                throw SQLError.createSQLException("Unable to create properties transform instance '" + propertiesTransformClassName + "' due to underlying exception: " + e.toString(), "01S00", null);
            }
            catch(IllegalAccessException e)
            {
                throw SQLError.createSQLException("Unable to create properties transform instance '" + propertiesTransformClassName + "' due to underlying exception: " + e.toString(), "01S00", null);
            }
            catch(ClassNotFoundException e)
            {
                throw SQLError.createSQLException("Unable to create properties transform instance '" + propertiesTransformClassName + "' due to underlying exception: " + e.toString(), "01S00", null);
            }
        if(Util.isColdFusion() && urlProps.getProperty("autoConfigureForColdFusion", "true").equalsIgnoreCase("true"))
        {
            String configs = urlProps.getProperty("useConfigs");
            StringBuffer newConfigs = new StringBuffer();
            if(configs != null)
            {
                newConfigs.append(configs);
                newConfigs.append(",");
            }
            newConfigs.append("coldFusion");
            urlProps.setProperty("useConfigs", newConfigs.toString());
        }
        String configNames = null;
        if(defaults != null)
            configNames = defaults.getProperty("useConfigs");
        if(configNames == null)
            configNames = urlProps.getProperty("useConfigs");
        if(configNames != null)
        {
            List splitNames = StringUtils.split(configNames, ",", true);
            Properties configProps = new Properties();
            Iterator namesIter = splitNames.iterator();
            do
            {
                if(!namesIter.hasNext())
                    break;
                String configName = (String)namesIter.next();
                try
                {
                    java.io.InputStream configAsStream = getClass().getResourceAsStream("configs/" + configName + ".properties");
                    if(configAsStream == null)
                        throw SQLError.createSQLException("Can't find configuration template named '" + configName + "'", "01S00", null);
                    configProps.load(configAsStream);
                }
                catch(IOException ioEx)
                {
                    SQLException sqlEx = SQLError.createSQLException("Unable to load configuration template '" + configName + "' due to underlying IOException: " + ioEx, "01S00", null);
                    sqlEx.initCause(ioEx);
                    throw sqlEx;
                }
            } while(true);
            String key;
            String property;
            for(Iterator propsIter = urlProps.keySet().iterator(); propsIter.hasNext(); configProps.setProperty(key, property))
            {
                key = propsIter.next().toString();
                property = urlProps.getProperty(key);
            }

            urlProps = configProps;
        }
        if(defaults != null)
        {
            String key;
            String property;
            for(Iterator propsIter = defaults.keySet().iterator(); propsIter.hasNext(); urlProps.setProperty(key, property))
            {
                key = propsIter.next().toString();
                property = defaults.getProperty(key);
            }

        }
        return urlProps;
    }

从上我们可以看出url解析实际上，是解析出host，port，db，查询参数
//获取mysql连接

com.mysql.jdbc.Connection newConn = ConnectionImpl.getInstance(host(props), port(props), props, database(props), url);

//ConnectionImpl

public class ConnectionImpl extends ConnectionPropertiesImpl
    implements Connection
{
    private static Map mapTransIsolationNameToValue;//事务隔离级别Map
    private static Timer cancelTimer;
    private static final Constructor JDBC_4_CONNECTION_CTOR;//jdbc4Connection构造函数
    private boolean autoCommit;//autoCommit
    private Map cachedPreparedStatementParams;
    private String characterSetMetadata;
    private String characterSetResultsOnServer;
    private Map charsetConverterMap;
    private long connectionId;//connectionId
    private String database;//database
    private DatabaseMetaData dbmd;
    private String host;//host
    private List hostList;
    private int hostListSize;
    private MysqlIO io;//MysqlIO
    private boolean isClientTzUTC;
    private boolean isClosed;
    private boolean isInGlobalTx;
    private boolean isRunningOnJDK13;
    private int isolationLevel;//事务隔离级别
    private final Object mutex;
    private String myURL;//myURL
    private boolean needsPing;
    private int netBufferLength;
    private boolean noBackslashEscapes;
    private Map openStatements;//statment Map
    private LRUCache parsedCallableStatementCache;//存储过程缓存
    private String password;//password
    private long perfMetricsHistBreakpoints[];
    private int perfMetricsHistCounts[];
    private Throwable pointOfOrigin;
    private int port;//port
    private boolean preferSlaveDuringFailover;
    protected Properties props;
    private long queriesIssuedFailedOver;
    private boolean readInfoMsg;
    private boolean readOnly;//readOnly
    protected LRUCache resultSetMetadataCache;//结果集缓存
    private TimeZone serverTimezoneTZ;//服务器TimeZone
    private Map serverVariables;
    private long shortestQueryTimeMs;
    private Map statementsUsingMaxRows;
    private double totalQueryTimeMs;
    private boolean transactionsSupported;
    private Map typeMap;
    private boolean useAnsiQuotes;
    private String user;//user
    private boolean useServerPreparedStmts;
    private LRUCache serverSideStatementCheckCache;
    private LRUCache serverSideStatementCache;
    private Calendar sessionCalendar;
    private Calendar utcCalendar;
    private String origHostToConnectTo;
    private int origPortToConnectTo;
    private String origDatabaseToConnectTo;
    private String errorMessageEncoding;
    private boolean usePlatformCharsetConverters;
    private boolean hasTriedMasterFlag;
    private String statementComment;
    private boolean storesLowerCaseTableName;
    private List statementInterceptors;
    private boolean requiresEscapingEncoder;
    private boolean usingCachedConfig;
    private int autoIncrementIncrement;

    static 
    {
        mapTransIsolationNameToValue = null;
        mapTransIsolationNameToValue = new HashMap(8);
	//五种事务隔离级别
        mapTransIsolationNameToValue.put("READ-UNCOMMITED", Constants.integerValueOf(1));
        mapTransIsolationNameToValue.put("READ-UNCOMMITTED", Constants.integerValueOf(1));
        mapTransIsolationNameToValue.put("READ-COMMITTED", Constants.integerValueOf(2));
        mapTransIsolationNameToValue.put("REPEATABLE-READ", Constants.integerValueOf(4));
        mapTransIsolationNameToValue.put("SERIALIZABLE", Constants.integerValueOf(8));
        boolean createdNamedTimer = false;
        try
        {
            Constructor ctr = (java.util.Timer.class).getConstructor(new Class[] {
                java.lang.String.class, Boolean.TYPE
            });
            cancelTimer = (Timer)ctr.newInstance(new Object[] {
                "MySQL Statement Cancellation Timer", Boolean.TRUE
            });
            createdNamedTimer = true;
        }
        catch(Throwable t)
        {
            createdNamedTimer = false;
        }
        if(!createdNamedTimer)
            cancelTimer = new Timer(true);
        if(Util.isJdbc4())
            try
            {
	        //获取JDBC4Connection的构造函数
                JDBC_4_CONNECTION_CTOR = Class.forName("com.mysql.jdbc.JDBC4Connection").getConstructor(new Class[] {
                    java.lang.String.class, Integer.TYPE, java.util.Properties.class, java.lang.String.class, java.lang.String.class
                });
            }
            catch(ClassNotFoundException e)
            {
                throw new RuntimeException(e);
            }
    }
    //获取Connection
   protected static Connection getInstance(String hostToConnectTo, int portToConnectTo, Properties info, String databaseToConnectTo, String url)
        throws SQLException
    {
        //如果不是jdbc4则返回ConnectionImpl，否则为JDBC4Connection
        if(!Util.isJdbc4())
            return new ConnectionImpl(hostToConnectTo, portToConnectTo, info, databaseToConnectTo, url);
        else
            return (Connection)Util.handleNewInstance(JDBC_4_CONNECTION_CTOR, new Object[] {
                hostToConnectTo, Constants.integerValueOf(portToConnectTo), info, databaseToConnectTo, url
            }, null);
    }
}

先看ConnectionImpl，
//ConnectionImpl

protected ConnectionImpl(String hostToConnectTo, int portToConnectTo, Properties info, String databaseToConnectTo, String url)
        throws SQLException
    {
        autoCommit = true;//自动提交为true
	//所有变量先赋值为null，待不用时，垃圾回收器，回收变量
        characterSetMetadata = null;
        characterSetResultsOnServer = null;
        charsetConverterMap = new HashMap(CharsetMapping.getNumberOfCharsetsConfigured());
        connectionCreationTimeMillis = 0L;
        database = null;
        dbmd = null;
        executingFailoverReconnect = false;
        failedOver = false;
        hasIsolationLevels = false;
        hasQuotedIdentifiers = false;
        host = null;
        hostList = null;
        hostListSize = 0;
        indexToCharsetMapping = CharsetMapping.INDEX_TO_CHARSET;
        io = null;
        isClientTzUTC = false;
        isClosed = true;
        isInGlobalTx = false;
        isRunningOnJDK13 = false;
        isolationLevel = 2;//默认隔离级别为READ-COMMITTED
        isServerTzUTC = false;
        lastQueryFinishedTime = 0L;
        log = NULL_LOGGER;
        longestQueryTimeMs = 0L;
        lowerCaseTableNames = false;
        masterFailTimeMillis = 0L;
        maximumNumberTablesAccessed = 0L;
        maxRowsChanged = false;
        minimumNumberTablesAccessed = 9223372036854775807L;
        mutex = new Object();//互斥量
        myURL = null;
        needsPing = false;
        netBufferLength = 16384;
        noBackslashEscapes = false;
        numberOfPreparedExecutes = 0L;
        numberOfPrepares = 0L;
        numberOfQueriesIssued = 0L;
        numberOfResultSetsCreated = 0L;
        oldHistBreakpoints = null;
        oldHistCounts = null;
        parserKnowsUnicode = false;
        password = null;
        port = 3306;
        preferSlaveDuringFailover = false;
        props = null;
        queriesIssuedFailedOver = 0L;
        readInfoMsg = false;
        readOnly = false;//默认读写
        serverTimezoneTZ = null;
        serverVariables = null;
        shortestQueryTimeMs = 9223372036854775807L;
        totalQueryTimeMs = 0.0D;
        transactionsSupported = false;
        useAnsiQuotes = false;
        user = null;
        useServerPreparedStmts = false;
        errorMessageEncoding = "Cp1252";
        hasTriedMasterFlag = false;
        statementComment = null;
        usingCachedConfig = false;
        autoIncrementIncrement = 0;
        charsetToNumBytesMap = new HashMap();
        connectionCreationTimeMillis = System.currentTimeMillis();
        pointOfOrigin = new Throwable();
        origHostToConnectTo = hostToConnectTo;
        origPortToConnectTo = portToConnectTo;
        origDatabaseToConnectTo = databaseToConnectTo;
        try
        {
            (java.sql.Blob.class).getMethod("truncate", new Class[] {
                Long.TYPE
            });
            isRunningOnJDK13 = false;
        }
        catch(NoSuchMethodException nsme)
        {
            isRunningOnJDK13 = true;
        }
        sessionCalendar = new GregorianCalendar();
        utcCalendar = new GregorianCalendar();
        utcCalendar.setTimeZone(TimeZone.getTimeZone("GMT"));
        log = LogFactory.getLogger(getLogger(), "MySQL", getExceptionInterceptor());
        defaultTimeZone = Util.getDefaultTimeZone();
        if("GMT".equalsIgnoreCase(defaultTimeZone.getID()))
            isClientTzUTC = true;
        else
            isClientTzUTC = false;
        openStatements = new HashMap();
        serverVariables = new HashMap();
	//初始化db信息，host，port，user，password等
        hostList = new ArrayList();
        if(hostToConnectTo == null)
        {
            host = "localhost";
            hostList.add(host);
        } else
        if(hostToConnectTo.indexOf(',') != -1)
        {
            for(StringTokenizer hostTokenizer = new StringTokenizer(hostToConnectTo, ",", false); hostTokenizer.hasMoreTokens(); hostList.add(hostTokenizer.nextToken().trim()));
        } else
        {
            host = hostToConnectTo;
            hostList.add(host);
        }
        hostListSize = hostList.size();
        port = portToConnectTo;
        if(databaseToConnectTo == null)
            databaseToConnectTo = "";
        database = databaseToConnectTo;
        myURL = url;
        user = info.getProperty("user");
        password = info.getProperty("password");
        if(user == null || user.equals(""))
            user = "";
        if(password == null)
            password = "";
        props = info;
	//初始化驱动属性
        initializeDriverProperties(info);
        try
        {
	    //初始化数据库元数据信息
	    //private DatabaseMetaData dbmd;
            dbmd = getMetaData(false, false);
	    //创建MysqlIO
            createNewIO(false);
	    //初始化mysqlStatement拦截器
            initializeStatementInterceptors();
	    //设置IO拦截器
            io.setStatementInterceptors(statementInterceptors);
        }
        catch(SQLException ex)
        {
	    //关闭mysqlIO
            cleanup(ex);
            throw ex;
        }
        catch(Exception ex)
        {
            cleanup(ex);
            StringBuffer mesg = new StringBuffer(128);
            if(!getParanoid())
            {
                mesg.append("Cannot connect to MySQL server on ");
                mesg.append(host);
                mesg.append(":");
                mesg.append(port);
                mesg.append(".\n\n");
                mesg.append("Make sure that there is a MySQL server ");
                mesg.append("running on the machine/port you are trying ");
                mesg.append("to connect to and that the machine this software is running on ");
                mesg.append("is able to connect to this host/port (i.e. not firewalled). ");
                mesg.append("Also make sure that the server has not been started with the --skip-networking ");
                mesg.append("flag.\n\n");
            } else
            {
                mesg.append("Unable to connect to database.");
            }
            SQLException sqlEx = SQLError.createSQLException(mesg.toString(), "08S01", getExceptionInterceptor());
            sqlEx.initCause(ex);
            throw sqlEx;
        }
    }

//初始化驱动属性
initializeDriverProperties(info);

private void initializeDriverProperties(Properties info)
        throws SQLException
    {
        initializeProperties(info);
        String exceptionInterceptorClasses = getExceptionInterceptors();
        if(exceptionInterceptorClasses != null && !"".equals(exceptionInterceptorClasses))
        {
            exceptionInterceptor = new ExceptionInterceptorChain(exceptionInterceptorClasses);
            exceptionInterceptor.init(this, info);
        }
        usePlatformCharsetConverters = getUseJvmCharsetConverters();
        log = LogFactory.getLogger(getLogger(), "MySQL", getExceptionInterceptor());
        if(getProfileSql() || getUseUsageAdvisor())
            eventSink = ProfilerEventHandlerFactory.getInstance(this);
        if(getCachePreparedStatements())
	    //创建PreparedStatement缓存
            createPreparedStatementCaches();
        if(getNoDatetimeStringSync() && getUseTimezone())
            throw SQLError.createSQLException("Can't enable noDatetimeSync and useTimezone configuration properties at the same time", "01S00", getExceptionInterceptor());
        if(getCacheCallableStatements())
	   //设置CallableStatement缓存
            parsedCallableStatementCache = new LRUCache(getCallableStatementCacheSize());
        if(getAllowMultiQueries())
            setCacheResultSetMetadata(false);
        if(getCacheResultSetMetadata())
	     //设置结果集缓存
            resultSetMetadataCache = new LRUCache(getMetadataCacheSize());
    }
  //初始化属性
 protected void initializeProperties(Properties info)
        throws SQLException
    {
        if(info != null)
        {
            String profileSqlLc = info.getProperty("profileSql");
            if(profileSqlLc != null)
                info.put("profileSQL", profileSqlLc);
            Properties infoCopy = (Properties)info.clone();
            infoCopy.remove("HOST");
            infoCopy.remove("user");
            infoCopy.remove("password");
            infoCopy.remove("DBNAME");
            infoCopy.remove("PORT");
            infoCopy.remove("profileSql");
            int numPropertiesToSet = PROPERTY_LIST.size();
            for(int i = 0; i < numPropertiesToSet; i++)
            {
                Field propertyField = (Field)PROPERTY_LIST.get(i);
                try
                {
                    ConnectionProperty propToSet = (ConnectionProperty)propertyField.get(this);
                    propToSet.initializeFrom(infoCopy);
                }
            }

            postInitialization();
        }
    }

//初始化数据库元数据信息
//private DatabaseMetaData dbmd;
dbmd = getMetaData(false, false);

 private DatabaseMetaData getMetaData(boolean checkClosed, boolean checkForInfoSchema)
        throws SQLException
    {
        if(checkClosed)
            checkClosed();
        return DatabaseMetaData.getInstance(this, database, checkForInfoSchema);
    }

//创建MysqlIO
createNewIO(false);

protected void createNewIO(boolean isForReconnect)
        throws SQLException
    {
        Object obj = mutex;
        JVM INSTR monitorenter ;
        Properties mergedProps;
        long queriesIssuedFailedOverCopy;
        mergedProps = exposeAsProperties(props);
        queriesIssuedFailedOverCopy = queriesIssuedFailedOver;
        queriesIssuedFailedOver = 0L;
	//对于Standyalone Sever情况
        if(!getHighAvailability() && !failedOver)
        {
            boolean connectionGood = false;
            Exception connectionNotEstablishedBecause = null;
            int hostIndex = 0;
            if(getRoundRobinLoadBalance())
                hostIndex = getNextRoundRobinHostIndex(getURL(), hostList);
            while(hostIndex < hostListSize) 
            {
                if(hostIndex == 0)
                    hasTriedMasterFlag = true;
                try
                {
                    String newHostPortPair = (String)hostList.get(hostIndex);
                    int newPort = 3306;
                    String hostPortPair[] = NonRegisteringDriver.parseHostPortPair(newHostPortPair);
                    String newHost = hostPortPair[0];
                    if(newHost == null || StringUtils.isEmptyOrWhitespaceOnly(newHost))
                        newHost = "localhost";
                    if(hostPortPair[1] != null)
                        try
                        {
                            newPort = Integer.parseInt(hostPortPair[1]);
                        }
                        catch(NumberFormatException nfe)
                        {
                            throw SQLError.createSQLException("Illegal connection port value '" + hostPortPair[1] + "'", "01S00", getExceptionInterceptor());
                        }
		     //创建MysqlIO
                    io = new MysqlIO(newHost, newPort, mergedProps, getSocketFactoryClassName(), this, getSocketTimeout(), largeRowSizeThreshold.getValueAsInt());
                    //握手
		    io.doHandshake(user, password, database);
		    //获取io的线程id
                    connectionId = io.getThreadId();
                    isClosed = false;
                    boolean oldAutoCommit = getAutoCommit();//AutoCommit
                    int oldIsolationLevel = isolationLevel;//事务隔离级别
                    boolean oldReadOnly = isReadOnly();//ReadOnly
                    String oldCatalog = getCatalog();
                    initializePropsFromServer();
                    if(isForReconnect)
                    {
                        setAutoCommit(oldAutoCommit);
                        if(hasIsolationLevels)
                            setTransactionIsolation(oldIsolationLevel);
                        setCatalog(oldCatalog);
                    }
                    if(hostIndex != 0)
                    {
                        setFailedOverState();
                        queriesIssuedFailedOverCopy = 0L;
                    } else
                    {
                        failedOver = false;
                        queriesIssuedFailedOverCopy = 0L;
                        if(hostListSize > 1)
                            setReadOnlyInternal(false);
                        else
                            setReadOnlyInternal(oldReadOnly);
                    }
                    connectionGood = true;
                    break;
                }
                catch(Exception EEE)
                {
                    if(io != null)
                        io.forceClose();
                    connectionNotEstablishedBecause = EEE;
                    connectionGood = false;
                    if(EEE instanceof SQLException)
                    {
                        SQLException sqlEx = (SQLException)EEE;
                        String sqlState = sqlEx.getSQLState();
                        if(sqlState == null || !sqlState.equals("08S01"))
                            throw sqlEx;
                    }
                    if(getRoundRobinLoadBalance())
                    {
                        hostIndex = getNextRoundRobinHostIndex(getURL(), hostList) - 1;
                        continue;
                    }
                    if(hostListSize - 1 == hostIndex)
                        throw SQLError.createCommunicationsException(this, io == null ? 0L : io.getLastPacketSentTimeMs(), io == null ? 0L : io.getLastPacketReceivedTimeMs(), EEE, getExceptionInterceptor());
                    hostIndex++;
                }
            }
            if(!connectionGood)
            {
                SQLException chainedEx = SQLError.createSQLException(Messages.getString("Connection.UnableToConnect"), "08001", getExceptionInterceptor());
                chainedEx.initCause(connectionNotEstablishedBecause);
                throw chainedEx;
            }
        } else
        {
	   //对于负载均衡集群
            double timeout = getInitialTimeout();
            boolean connectionGood = false;
            Exception connectionException = null;
            int hostIndex = 0;
            if(getRoundRobinLoadBalance())
                hostIndex = getNextRoundRobinHostIndex(getURL(), hostList);
            for(; hostIndex < hostListSize && !connectionGood; hostIndex++)
            {
                if(hostIndex == 0)
                    hasTriedMasterFlag = true;
                if(preferSlaveDuringFailover && hostIndex == 0)
                    hostIndex++;
                for(int attemptCount = 0; attemptCount < getMaxReconnects() && !connectionGood; attemptCount++)
                {
                    try
                    {
                        if(io != null)
                            io.forceClose();
                        String newHostPortPair = (String)hostList.get(hostIndex);
                        int newPort = 3306;
                        String hostPortPair[] = NonRegisteringDriver.parseHostPortPair(newHostPortPair);
                        String newHost = hostPortPair[0];
                        if(newHost == null || StringUtils.isEmptyOrWhitespaceOnly(newHost))
                            newHost = "localhost";
                        if(hostPortPair[1] != null)
                            try
                            {
                                newPort = Integer.parseInt(hostPortPair[1]);
                            }
                            catch(NumberFormatException nfe)
                            {
                                throw SQLError.createSQLException("Illegal connection port value '" + hostPortPair[1] + "'", "01S00", getExceptionInterceptor());
                            }
			//创建MysqlIO
                        io = new MysqlIO(newHost, newPort, mergedProps, getSocketFactoryClassName(), this, getSocketTimeout(), largeRowSizeThreshold.getValueAsInt());
                        //握手
			io.doHandshake(user, password, database);
                        pingInternal(false, 0);
                         //获取io的线程id
                        connectionId = io.getThreadId();
                        isClosed = false;
                        boolean oldAutoCommit = getAutoCommit();//AutoCommit
                        int oldIsolationLevel = isolationLevel;//事务级别
                        boolean oldReadOnly = isReadOnly();//ReadOnly
                        String oldCatalog = getCatalog();
                        initializePropsFromServer();
                        if(isForReconnect)
                        {
                            setAutoCommit(oldAutoCommit);
                            if(hasIsolationLevels)
                                setTransactionIsolation(oldIsolationLevel);
                            setCatalog(oldCatalog);
                        }
                        connectionGood = true;
                        if(hostIndex != 0)
                        {
                            setFailedOverState();
                            queriesIssuedFailedOverCopy = 0L;
                            break;
                        }
                        failedOver = false;
                        queriesIssuedFailedOverCopy = 0L;
                        if(hostListSize > 1)
                            setReadOnlyInternal(false);
                        else
                            setReadOnlyInternal(oldReadOnly);
                        break;
                    }
                    catch(Exception EEE)
                    {
                        connectionException = EEE;
                    }
                    connectionGood = false;
                    if(getRoundRobinLoadBalance())
                        hostIndex = getNextRoundRobinHostIndex(getURL(), hostList) - 1;
                    if(connectionGood)
                        break;
                    if(attemptCount <= 0)
                        continue;
                    try
                    {
                        Thread.sleep((long)timeout * 1000L);
                    }
                    catch(InterruptedException IE) { }
                }

            }

            if(!connectionGood)
            {
                SQLException chainedEx = SQLError.createSQLException(Messages.getString("Connection.UnableToConnectWithRetries", new Object[] {
                    new Integer(getMaxReconnects())
                }), "08001", getExceptionInterceptor());
                chainedEx.initCause(connectionException);
                throw chainedEx;
            }
        }
        if(getParanoid() && !getHighAvailability() && hostListSize <= 1)
        {
            password = null;
            user = null;
        }
        if(isForReconnect)
        {
            Iterator statementIter = openStatements.values().iterator();
            Stack serverPreparedStatements = null;
            do
            {
                if(!statementIter.hasNext())
                    break;
                Object statementObj = statementIter.next();
                if(statementObj instanceof ServerPreparedStatement)
                {
                    if(serverPreparedStatements == null)
                        serverPreparedStatements = new Stack();
                    serverPreparedStatements.add(statementObj);
                }
            } while(true);
            if(serverPreparedStatements != null)
                for(; !serverPreparedStatements.isEmpty(); ((ServerPreparedStatement)serverPreparedStatements.pop()).rePrepare());
        }
        queriesIssuedFailedOver = queriesIssuedFailedOverCopy;
        break MISSING_BLOCK_LABEL_1241;
        Exception exception;
        exception;
        queriesIssuedFailedOver = queriesIssuedFailedOverCopy;
        throw exception;
        Exception exception1;
        exception1;
        throw exception1;
 }

//初始化mysqlStatement拦截器
initializeStatementInterceptors();

   protected void initializeStatementInterceptors()
        throws SQLException
    {
        statementInterceptors = Util.loadExtensions(this, props, getStatementInterceptors(), "MysqlIo.BadStatementInterceptor", getExceptionInterceptor());
    }

//设置IO拦截器

io.setStatementInterceptors(statementInterceptors);

//关闭mysqlIO

private void cleanup(Throwable whyCleanedUp)
    {
        try
        {
            if(io != null && !isClosed())
                realClose(false, false, false, whyCleanedUp);
            else
            if(io != null)
                io.forceClose();
        }
        catch(SQLException sqlEx) { }
        isClosed = true;
    }

从上面的分析，可以看出从DriverManager获取连接，实际上是事委托给com.mysql.jdbc.Driver,com.mysql.jdbc.Driver实际调用的是NonRegisteringDriver获取连接方法，首先分析url，如果url以jdbc:mysql:loadbalance://或jdbc:mysql:replication://开头，则调用负载均衡，集群的连接获取方法；如果是单机服务器，根据jdbc4的属性，创建相应的连接；如果不是jdbc4类型，则创建ConnectionImpl实例，初始化连接事务级别，db信息，autoCommit，readonly等属性，初始化驱动属性，创建PreparedStatement缓存，设置CallableStatement缓存，设置结果集缓存，初始化数据库元数据信息DatabaseMetaData，创建MysqlIO，初始化mysqlStatement拦截器，设置IO拦截器。

下面来看一下jdbc4连接：

//JDBC4Connection

public class JDBC4Connection extends ConnectionImpl
{


  public JDBC4Connection(String hostToConnectTo, int portToConnectTo, Properties info, String databaseToConnectTo, String url)
        throws SQLException
    {
        super(hostToConnectTo, portToConnectTo, info, databaseToConnectTo, url);
    }
    private JDBC4ClientInfoProvider infoProvider;
}

从上面可以看出JDBC4Connection是ConnectionImpl的包装。
至此mysql连接的获取讲完，下一篇，看一下集群及负载均衡的连接获取。

//NonRegisteringDriver

public class NonRegisteringDriver
    implements Driver
{
   //返回host，无返回localhost
   public String host(Properties props)
    {
        return props.getProperty("HOST", "localhost");
    }
    public String database(Properties props)
    {
        return props.getProperty("DBNAME");
    }
     //返回PORT，无返回3306
     public int port(Properties props)
    {
        return Integer.parseInt(props.getProperty("PORT", "3306"));
    }
    private static final String REPLICATION_URL_PREFIX = "jdbc:mysql:replication://";
    private static final String URL_PREFIX = "jdbc:mysql://";
    private static final String MXJ_URL_PREFIX = "jdbc:mysql:mxj://";
    private static final String LOADBALANCE_URL_PREFIX = "jdbc:mysql:loadbalance://";
    public static final String DBNAME_PROPERTY_KEY = "DBNAME";
    public static final boolean DEBUG = false;
    public static final int HOST_NAME_INDEX = 0;
    public static final String HOST_PROPERTY_KEY = "HOST";
    public static final String PASSWORD_PROPERTY_KEY = "password";
    public static final int PORT_NUMBER_INDEX = 1;
    public static final String PORT_PROPERTY_KEY = "PORT";
    public static final String PROPERTIES_TRANSFORM_KEY = "propertiesTransform";
    public static final boolean TRACE = false;
    public static final String USE_CONFIG_PROPERTY_KEY = "useConfigs";
    public static final String USER_PROPERTY_KEY = "user";
}

//ConnectionImpl

public class ConnectionImpl extends ConnectionPropertiesImpl
    implements Connection
{
   
    private static final String JDBC_LOCAL_CHARACTER_SET_RESULTS = "jdbc.local.character_set_results";
    private static final Object CHARSET_CONVERTER_NOT_AVAILABLE_MARKER = new Object();
    public static Map charsetMap;
    protected static final String DEFAULT_LOGGER_CLASS = "com.mysql.jdbc.log.StandardLogger";
    private static final int HISTOGRAM_BUCKETS = 20;
    private static final String LOGGER_INSTANCE_NAME = "MySQL";
    private static Map mapTransIsolationNameToValue;
    private static final Log NULL_LOGGER = new NullLogger("MySQL");
    private static Map roundRobinStatsMap;
    private static final Map serverCollationByUrl = new HashMap();
    private static final Map serverConfigByUrl = new HashMap();
    private long queryTimeCount;
    private double queryTimeSum;
    private double queryTimeSumSquares;
    private double queryTimeMean;
    private static Timer cancelTimer;
    private List connectionLifecycleInterceptors;
    private static final Constructor JDBC_4_CONNECTION_CTOR;
    private static final int DEFAULT_RESULT_SET_TYPE = 1003;
    private static final int DEFAULT_RESULT_SET_CONCURRENCY = 1007;
    private boolean autoCommit;
    private Map cachedPreparedStatementParams;
    private String characterSetMetadata;
    private String characterSetResultsOnServer;
    private Map charsetConverterMap;
    private Map charsetToNumBytesMap;
    private long connectionCreationTimeMillis;
    private long connectionId;
    private String database;
    private DatabaseMetaData dbmd;
    private TimeZone defaultTimeZone;
    private ProfilerEventHandler eventSink;
    private boolean executingFailoverReconnect;
    private boolean failedOver;
    private Throwable forceClosedReason;
    private Throwable forcedClosedLocation;
    private boolean hasIsolationLevels;
    private boolean hasQuotedIdentifiers;
    private String host;
    private List hostList;
    private int hostListSize;
    private String indexToCharsetMapping[];
    private MysqlIO io;
    private boolean isClientTzUTC;
    private boolean isClosed;
    private boolean isInGlobalTx;
    private boolean isRunningOnJDK13;
    private int isolationLevel;
    private boolean isServerTzUTC;
    private long lastQueryFinishedTime;
    private Log log;
    private long longestQueryTimeMs;
    private boolean lowerCaseTableNames;
    private long masterFailTimeMillis;
    private long maximumNumberTablesAccessed;
    private boolean maxRowsChanged;
    private long metricsLastReportedMs;
    private long minimumNumberTablesAccessed;
    private final Object mutex;
    private String myURL;
    private boolean needsPing;
    private int netBufferLength;
    private boolean noBackslashEscapes;
    private long numberOfPreparedExecutes;
    private long numberOfPrepares;
    private long numberOfQueriesIssued;
    private long numberOfResultSetsCreated;
    private long numTablesMetricsHistBreakpoints[];
    private int numTablesMetricsHistCounts[];
    private long oldHistBreakpoints[];
    private int oldHistCounts[];
    private Map openStatements;
    private LRUCache parsedCallableStatementCache;
    private boolean parserKnowsUnicode;
    private String password;
    private long perfMetricsHistBreakpoints[];
    private int perfMetricsHistCounts[];
    private Throwable pointOfOrigin;
    private int port;
    private boolean preferSlaveDuringFailover;
    protected Properties props;
    private long queriesIssuedFailedOver;
    private boolean readInfoMsg;
    private boolean readOnly;
    protected LRUCache resultSetMetadataCache;
    private TimeZone serverTimezoneTZ;
    private Map serverVariables;
    private long shortestQueryTimeMs;
    private Map statementsUsingMaxRows;
    private double totalQueryTimeMs;
    private boolean transactionsSupported;
    private Map typeMap;
    private boolean useAnsiQuotes;
    private String user;
    private boolean useServerPreparedStmts;
    private LRUCache serverSideStatementCheckCache;
    private LRUCache serverSideStatementCache;
    private Calendar sessionCalendar;
    private Calendar utcCalendar;
    private String origHostToConnectTo;
    private int origPortToConnectTo;
    private String origDatabaseToConnectTo;
    private String errorMessageEncoding;
    private boolean usePlatformCharsetConverters;
    private boolean hasTriedMasterFlag;
    private String statementComment;
    private boolean storesLowerCaseTableName;
    private List statementInterceptors;
    private boolean requiresEscapingEncoder;
    private boolean usingCachedConfig;
    private int autoIncrementIncrement;
    private ExceptionInterceptor exceptionInterceptor;
}

//DatabaseMetaData

public class DatabaseMetaData
    implements java.sql.DatabaseMetaData
{
 private static String mysqlKeywordsThatArentSQL92;
    protected static final int MAX_IDENTIFIER_LENGTH = 64;
    private static final int DEFERRABILITY = 13;
    private static final int DELETE_RULE = 10;
    private static final int FK_NAME = 11;
    private static final int FKCOLUMN_NAME = 7;
    private static final int FKTABLE_CAT = 4;
    private static final int FKTABLE_NAME = 6;
    private static final int FKTABLE_SCHEM = 5;
    private static final int KEY_SEQ = 8;
    private static final int PK_NAME = 12;
    private static final int PKCOLUMN_NAME = 3;
    private static final int PKTABLE_CAT = 0;
    private static final int PKTABLE_NAME = 2;
    private static final int PKTABLE_SCHEM = 1;
    private static final String SUPPORTS_FK = "SUPPORTS_FK";
    private static final byte TABLE_AS_BYTES[] = "TABLE".getBytes();
    private static final byte SYSTEM_TABLE_AS_BYTES[] = "SYSTEM TABLE".getBytes();
    private static final int UPDATE_RULE = 9;
    private static final byte VIEW_AS_BYTES[] = "VIEW".getBytes();
    private static final Constructor JDBC_4_DBMD_SHOW_CTOR;
    private static final Constructor JDBC_4_DBMD_IS_CTOR;
    protected ConnectionImpl conn;
    protected String database;
    protected String quotedId;
    private ExceptionInterceptor exceptionInterceptor;

    static 
    {
        if(Util.isJdbc4())
        {
            try
            {
                JDBC_4_DBMD_SHOW_CTOR = Class.forName("com.mysql.jdbc.JDBC4DatabaseMetaData").getConstructor(new Class[] {
                    com.mysql.jdbc.ConnectionImpl.class, java.lang.String.class
                });
                JDBC_4_DBMD_IS_CTOR = Class.forName("com.mysql.jdbc.JDBC4DatabaseMetaDataUsingInfoSchema").getConstructor(new Class[] {
                    com.mysql.jdbc.ConnectionImpl.class, java.lang.String.class
                });
            }
            catch(SecurityException e)
            {
                throw new RuntimeException(e);
            }
            catch(NoSuchMethodException e)
            {
                throw new RuntimeException(e);
            }
            catch(ClassNotFoundException e)
            {
                throw new RuntimeException(e);
            }
        } else
        {
            JDBC_4_DBMD_IS_CTOR = null;
            JDBC_4_DBMD_SHOW_CTOR = null;
        }
	//mysql关键字
        String allMySQLKeywords[] = {
            "ACCESSIBLE", "ADD", "ALL", "ALTER", "ANALYZE", "AND", "AS", "ASC", "ASENSITIVE", "BEFORE", 
            "BETWEEN", "BIGINT", "BINARY", "BLOB", "BOTH", "BY", "CALL", "CASCADE", "CASE", "CHANGE", 
            "CHAR", "CHARACTER", "CHECK", "COLLATE", "COLUMN", "CONDITION", "CONNECTION", "CONSTRAINT", "CONTINUE", "CONVERT", 
            "CREATE", "CROSS", "CURRENT_DATE", "CURRENT_TIME", "CURRENT_TIMESTAMP", "CURRENT_USER", "CURSOR", "DATABASE", "DATABASES", "DAY_HOUR", 
            "DAY_MICROSECOND", "DAY_MINUTE", "DAY_SECOND", "DEC", "DECIMAL", "DECLARE", "DEFAULT", "DELAYED", "DELETE", "DESC", 
            "DESCRIBE", "DETERMINISTIC", "DISTINCT", "DISTINCTROW", "DIV", "DOUBLE", "DROP", "DUAL", "EACH", "ELSE", 
            "ELSEIF", "ENCLOSED", "ESCAPED", "EXISTS", "EXIT", "EXPLAIN", "FALSE", "FETCH", "FLOAT", "FLOAT4", 
            "FLOAT8", "FOR", "FORCE", "FOREIGN", "FROM", "FULLTEXT", "GRANT", "GROUP", "HAVING", "HIGH_PRIORITY", 
            "HOUR_MICROSECOND", "HOUR_MINUTE", "HOUR_SECOND", "IF", "IGNORE", "IN", "INDEX", "INFILE", "INNER", "INOUT", 
            "INSENSITIVE", "INSERT", "INT", "INT1", "INT2", "INT3", "INT4", "INT8", "INTEGER", "INTERVAL", 
            "INTO", "IS", "ITERATE", "JOIN", "KEY", "KEYS", "KILL", "LEADING", "LEAVE", "LEFT", 
            "LIKE", "LIMIT", "LINEAR", "LINES", "LOAD", "LOCALTIME", "LOCALTIMESTAMP", "LOCK", "LONG", "LONGBLOB", 
            "LONGTEXT", "LOOP", "LOW_PRIORITY", "MATCH", "MEDIUMBLOB", "MEDIUMINT", "MEDIUMTEXT", "MIDDLEINT", "MINUTE_MICROSECOND", "MINUTE_SECOND", 
            "MOD", "MODIFIES", "NATURAL", "NOT", "NO_WRITE_TO_BINLOG", "NULL", "NUMERIC", "ON", "OPTIMIZE", "OPTION", 
            "OPTIONALLY", "OR", "ORDER", "OUT", "OUTER", "OUTFILE", "PRECISION", "PRIMARY", "PROCEDURE", "PURGE", 
            "RANGE", "READ", "READS", "READ_ONLY", "READ_WRITE", "REAL", "REFERENCES", "REGEXP", "RELEASE", "RENAME", 
            "REPEAT", "REPLACE", "REQUIRE", "RESTRICT", "RETURN", "REVOKE", "RIGHT", "RLIKE", "SCHEMA", "SCHEMAS", 
            "SECOND_MICROSECOND", "SELECT", "SENSITIVE", "SEPARATOR", "SET", "SHOW", "SMALLINT", "SPATIAL", "SPECIFIC", "SQL", 
            "SQLEXCEPTION", "SQLSTATE", "SQLWARNING", "SQL_BIG_RESULT", "SQL_CALC_FOUND_ROWS", "SQL_SMALL_RESULT", "SSL", "STARTING", "STRAIGHT_JOIN", "TABLE", 
            "TERMINATED", "THEN", "TINYBLOB", "TINYINT", "TINYTEXT", "TO", "TRAILING", "TRIGGER", "TRUE", "UNDO", 
            "UNION", "UNIQUE", "UNLOCK", "UNSIGNED", "UPDATE", "USAGE", "USE", "USING", "UTC_DATE", "UTC_TIME", 
            "UTC_TIMESTAMP", "VALUES", "VARBINARY", "VARCHAR", "VARCHARACTER", "VARYING", "WHEN", "WHERE", "WHILE", "WITH", 
            "WRITE", "X509", "XOR", "YEAR_MONTH", "ZEROFILL"
        };
	//sql92关键字
        String sql92Keywords[] = {
            "ABSOLUTE", "EXEC", "OVERLAPS", "ACTION", "EXECUTE", "PAD", "ADA", "EXISTS", "PARTIAL", "ADD", 
            "EXTERNAL", "PASCAL", "ALL", "EXTRACT", "POSITION", "ALLOCATE", "FALSE", "PRECISION", "ALTER", "FETCH", 
            "PREPARE", "AND", "FIRST", "PRESERVE", "ANY", "FLOAT", "PRIMARY", "ARE", "FOR", "PRIOR", 
            "AS", "FOREIGN", "PRIVILEGES", "ASC", "FORTRAN", "PROCEDURE", "ASSERTION", "FOUND", "PUBLIC", "AT", 
            "FROM", "READ", "AUTHORIZATION", "FULL", "REAL", "AVG", "GET", "REFERENCES", "BEGIN", "GLOBAL", 
            "RELATIVE", "BETWEEN", "GO", "RESTRICT", "BIT", "GOTO", "REVOKE", "BIT_LENGTH", "GRANT", "RIGHT", 
            "BOTH", "GROUP", "ROLLBACK", "BY", "HAVING", "ROWS", "CASCADE", "HOUR", "SCHEMA", "CASCADED", 
            "IDENTITY", "SCROLL", "CASE", "IMMEDIATE", "SECOND", "CAST", "IN", "SECTION", "CATALOG", "INCLUDE", 
            "SELECT", "CHAR", "INDEX", "SESSION", "CHAR_LENGTH", "INDICATOR", "SESSION_USER", "CHARACTER", "INITIALLY", "SET", 
            "CHARACTER_LENGTH", "INNER", "SIZE", "CHECK", "INPUT", "SMALLINT", "CLOSE", "INSENSITIVE", "SOME", "COALESCE", 
            "INSERT", "SPACE", "COLLATE", "INT", "SQL", "COLLATION", "INTEGER", "SQLCA", "COLUMN", "INTERSECT", 
            "SQLCODE", "COMMIT", "INTERVAL", "SQLERROR", "CONNECT", "INTO", "SQLSTATE", "CONNECTION", "IS", "SQLWARNING", 
            "CONSTRAINT", "ISOLATION", "SUBSTRING", "CONSTRAINTS", "JOIN", "SUM", "CONTINUE", "KEY", "SYSTEM_USER", "CONVERT", 
            "LANGUAGE", "TABLE", "CORRESPONDING", "LAST", "TEMPORARY", "COUNT", "LEADING", "THEN", "CREATE", "LEFT", 
            "TIME", "CROSS", "LEVEL", "TIMESTAMP", "CURRENT", "LIKE", "TIMEZONE_HOUR", "CURRENT_DATE", "LOCAL", "TIMEZONE_MINUTE", 
            "CURRENT_TIME", "LOWER", "TO", "CURRENT_TIMESTAMP", "MATCH", "TRAILING", "CURRENT_USER", "MAX", "TRANSACTION", "CURSOR", 
            "MIN", "TRANSLATE", "DATE", "MINUTE", "TRANSLATION", "DAY", "MODULE", "TRIM", "DEALLOCATE", "MONTH", 
            "TRUE", "DEC", "NAMES", "UNION", "DECIMAL", "NATIONAL", "UNIQUE", "DECLARE", "NATURAL", "UNKNOWN", 
            "DEFAULT", "NCHAR", "UPDATE", "DEFERRABLE", "NEXT", "UPPER", "DEFERRED", "NO", "USAGE", "DELETE", 
            "NONE", "USER", "DESC", "NOT", "USING", "DESCRIBE", "NULL", "VALUE", "DESCRIPTOR", "NULLIF", 
            "VALUES", "DIAGNOSTICS", "NUMERIC", "VARCHAR", "DISCONNECT", "OCTET_LENGTH", "VARYING", "DISTINCT", "OF", "VIEW", 
            "DOMAIN", "ON", "WHEN", "DOUBLE", "ONLY", "WHENEVER", "DROP", "OPEN", "WHERE", "ELSE", 
            "OPTION", "WITH", "END", "OR", "WORK", "END-EXEC", "ORDER", "WRITE", "ESCAPE", "OUTER", 
            "YEAR", "EXCEPT", "OUTPUT", "ZONE", "EXCEPTION"
        };
        TreeMap mySQLKeywordMap = new TreeMap();
        for(int i = 0; i < allMySQLKeywords.length; i++)
            mySQLKeywordMap.put(allMySQLKeywords[i], null);

        HashMap sql92KeywordMap = new HashMap(sql92Keywords.length);
        for(int i = 0; i < sql92Keywords.length; i++)
            sql92KeywordMap.put(sql92Keywords[i], null);

        Iterator it;
        for(it = sql92KeywordMap.keySet().iterator(); it.hasNext(); mySQLKeywordMap.remove(it.next()));
        StringBuffer keywordBuf = new StringBuffer();
        it = mySQLKeywordMap.keySet().iterator();
        if(it.hasNext())
            keywordBuf.append(it.next().toString());
        for(; it.hasNext(); keywordBuf.append(it.next().toString()))
            keywordBuf.append(",");

        mysqlKeywordsThatArentSQL92 = keywordBuf.toString();
    }

//Util

public class Util
{
	public static boolean isJdbc4()
    {
        return isJdbc4;
    }
    protected static Method systemNanoTimeMethod;
    private static Method CAST_METHOD;
    private static final TimeZone DEFAULT_TIMEZONE = TimeZone.getDefault();
    private static Util enclosingInstance = new Util();
    private static boolean isJdbc4 = false;
    private static boolean isColdFusion = false;

    static 
    {
        try
        {
            systemNanoTimeMethod = (java.lang.System.class).getMethod("nanoTime", null);
        }
        catch(SecurityException e)
        {
            systemNanoTimeMethod = null;
        }
        catch(NoSuchMethodException e)
        {
            systemNanoTimeMethod = null;
        }
        try
        {
            CAST_METHOD = (java.lang.Class.class).getMethod("cast", new Class[] {
                java.lang.Object.class
            });
        }
        catch(Throwable t) { }
        try
        {
	   //如果加载java.sql.NClob正常，则isJdbc4为true
            Class.forName("java.sql.NClob");
            isJdbc4 = true;
        }
        catch(Throwable t)
        {
            isJdbc4 = false;
        }
        String loadedFrom = stackTraceToString(new Throwable());
        if(loadedFrom != null)
            isColdFusion = loadedFrom.indexOf("coldfusion") != -1;
        else
            isColdFusion = false;
    }
    //构造className
    public static Object getInstance(String className, Class argTypes[], Object args[], ExceptionInterceptor exceptionInterceptor)
        throws SQLException
    {
        return handleNewInstance(Class.forName(className).getConstructor(argTypes), args, exceptionInterceptor);
        SecurityException e;
        e;
        throw SQLError.createSQLException("Can't instantiate required class", "S1000", e, exceptionInterceptor);
        e;
        throw SQLError.createSQLException("Can't instantiate required class", "S1000", e, exceptionInterceptor);
        e;
        throw SQLError.createSQLException("Can't instantiate required class", "S1000", e, exceptionInterceptor);
    }
    //根据Constructor，args创建，构建object
    public static final Object handleNewInstance(Constructor ctor, Object args[], ExceptionInterceptor exceptionInterceptor)
        throws SQLException
    {
        return ctor.newInstance(args);
        IllegalArgumentException e;
        e;
        throw SQLError.createSQLException("Can't instantiate required class", "S1000", e, exceptionInterceptor);
        e;
        throw SQLError.createSQLException("Can't instantiate required class", "S1000", e, exceptionInterceptor);
        e;
        throw SQLError.createSQLException("Can't instantiate required class", "S1000", e, exceptionInterceptor);
        e;
        Throwable target = e.getTargetException();
        if(target instanceof SQLException)
            throw (SQLException)target;
        if(target instanceof ExceptionInInitializerError)
            target = ((ExceptionInInitializerError)target).getException();
        throw SQLError.createSQLException(target.toString(), "S1000", exceptionInterceptor);
    }

    public static boolean interfaceExists(String hostname)
    {
        Class networkInterfaceClass = Class.forName("java.net.NetworkInterface");
        return networkInterfaceClass.getMethod("getByName", null).invoke(networkInterfaceClass, new Object[] {
            hostname
        }) != null;
        Throwable t;
        t;
        return false;
    }

    public static Object cast(Object invokeOn, Object toCast)
    {
        if(CAST_METHOD == null)
            break MISSING_BLOCK_LABEL_25;
        return CAST_METHOD.invoke(invokeOn, new Object[] {
            toCast
        });
        Throwable t;
        t;
        return null;
        return null;
    }
}

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Mysql负载均衡连接的获取 | JDBC驱动初始化-Mysql

2016-11-30 12:44
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