一，当连接创建完成时，接着就创建Statement进行sql查询，并返回相应的ResultSet

进入ConnectionImpl类下的，createStatement(..)

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public java.sql.Statement createStatement(int resultSetType,
			int resultSetConcurrency, int resultSetHoldability)
			throws SQLException {
               //对返回的结果集进行指定相应的模式功能,可参照ResultSet的常量设置
		if (getPedantic()) {
			if (resultSetHoldability != java.sql.ResultSet.HOLD_CURSORS_OVER_COMMIT) {
				throw SQLError.createSQLException(
						"HOLD_CUSRORS_OVER_COMMIT is only supported holdability level",
						SQLError.SQL_STATE_ILLEGAL_ARGUMENT, getExceptionInterceptor());
			}
		}

		return createStatement(resultSetType, resultSetConcurrency);
	}





public java.sql.Statement createStatement(int resultSetType,
			int resultSetConcurrency) throws SQLException {
		checkClosed();
                //getLoadBalanceSafeProxy() 为相应的连接
		StatementImpl stmt = new 
StatementImpl(getLoadBalanceSafeProxy(), this.database);
		stmt.setResultSetType(resultSetType);
		stmt.setResultSetConcurrency(resultSetConcurrency);

		return stmt;
	}

进入StatementImpl .executeQuery(..)

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public synchronized java.sql.ResultSet executeQuery(String sql)
			throws SQLException {
		checkClosed();
		//参数所传的连接对象
		MySQLConnection locallyScopedConn = this.connection;

		synchronized (locallyScopedConn) {
			this.retrieveGeneratedKeys = false;
			
			resetCancelledState();

			checkNullOrEmptyQuery(sql);

			//We only stream result sets when they are forward-only, read-only, and thefetch size has been set to Integer.MIN_VALUE
			boolean doStreaming = createStreamingResultSet();


			if (doStreaming
					&& this.connection.getNetTimeoutForStreamingResults() > 0) {
				executeSimpleNonQuery(locallyScopedConn, "SET net_write_timeout="
						+ this.connection.getNetTimeoutForStreamingResults());
			}

			if (this.doEscapeProcessing) {
				Object escapedSqlResult = EscapeProcessor.escapeSQL(sql,
						locallyScopedConn.serverSupportsConvertFn(), this.connection);

				if (escapedSqlResult instanceof String) {
					sql = (String) escapedSqlResult;
				} else {
					sql = ((EscapeProcessorResult) escapedSqlResult).escapedSql;
				}
			}

			char firstStatementChar = StringUtils.firstNonWsCharUc(sql,
					findStartOfStatement(sql));

			if (sql.charAt(0) == '/') {
				if (sql.startsWith(PING_MARKER)) {
					doPingInstead();
				
					return this.results;
				}
			}
			
			checkForDml(sql, firstStatementChar);

			if (this.results != null) {
				if (!locallyScopedConn.getHoldResultsOpenOverStatementClose()) {
					this.results.realClose(false);
				}
			}

			CachedResultSetMetaData cachedMetaData = null;

			// If there isn't a limit clause in the SQL
			// then limit the number of rows to return in
			// an efficient manner. Only do this if
			// setMaxRows() hasn't been used on any Statements
			// generated from the current Connection (saves
			// a query, and network traffic).

			if (useServerFetch()) {
				this.results = createResultSetUsingServerFetch(sql);

				return this.results;
			}

			CancelTask timeoutTask = null;

			String oldCatalog = null;

			try {
				if (locallyScopedConn.getEnableQueryTimeouts() &&
						this.timeoutInMillis != 0
						&& locallyScopedConn.versionMeetsMinimum(5, 0, 0)) {
					timeoutTask = new CancelTask(this);
					locallyScopedConn.getCancelTimer().schedule(timeoutTask,
							this.timeoutInMillis);
				}

				if (!locallyScopedConn.getCatalog().equals(this.currentCatalog)) {
					oldCatalog = locallyScopedConn.getCatalog();
					locallyScopedConn.setCatalog(this.currentCatalog);
				}

				//
				// Check if we have cached metadata for this query...
				//

				Field[] cachedFields = null;

				//是否应用缓存ResultSet
				if (locallyScopedConn.getCacheResultSetMetadata()) {
					cachedMetaData = locallyScopedConn.getCachedMetaData(sql);

					if (cachedMetaDat