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JDBC Driver for Google Cloud Spanner
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/*-------------------------------------------------------------------------
*
* Copyright (c) 2005-2014, PostgreSQL Global Development Group
*
*
*-------------------------------------------------------------------------
*/

package nl.topicus.jdbc;

import java.io.PrintWriter;
import java.sql.DriverManager;
import java.text.FieldPosition;
import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * Poor man's logging infrastructure. This just deals with maintaining a per-
 * connection ID and log level, and timestamping output.
 * 
 * This implementation is based on the implementation of PostgreSQL.
 * 
 * PostgreSQL is released under the PostgreSQL License, a liberal Open Source
 * license, similar to the BSD or MIT licenses.
 *
 * PostgreSQL Database Management System (formerly known as Postgres, then as
 * Postgres95)
 *
 * Portions Copyright (c) 1996-2017, The PostgreSQL Global Development Group
 *
 * Portions Copyright (c) 1994, The Regents of the University of California
 *
 * IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR
 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
 * LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION,
 * EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS ON AN
 * "AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATIONS TO PROVIDE
 * MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
 * 
 * @author loite
 */
public final class Logger
{
	// For brevity we only log the time, not date or timezone (the main reason
	// for the timestamp is to see delays etc. between log lines, not to pin
	// down an instant in time)
	private final SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss.SSS ");
	private final FieldPosition dummyPosition = new FieldPosition(0);
	private final StringBuffer buffer = new StringBuffer();
	private final String connectionIDString;

	private int level = 0;

	public Logger()
	{
		connectionIDString = "(driver) ";
	}

	public Logger(int connectionID)
	{
		connectionIDString = "(" + connectionID + ") ";
	}

	public void setLogLevel(int level)
	{
		this.level = level;
	}

	public int getLogLevel()
	{
		return level;
	}

	public boolean logDebug()
	{
		return level >= CloudSpannerDriver.DEBUG;
	}

	public boolean logInfo()
	{
		return level >= CloudSpannerDriver.INFO;
	}

	public void debug(String str)
	{
		debug(str, null);
	}

	public void debug(String str, Throwable t)
	{
		if (logDebug())
		{
			log(str, t);
		}
	}

	public void info(String str)
	{
		info(str, null);
	}

	public void info(String str, Throwable t)
	{
		if (logInfo())
		{
			log(str, t);
		}
	}

	public void log(String str, Throwable t)
	{
		PrintWriter writer = DriverManager.getLogWriter();
		if (writer == null)
		{
			return;
		}

		synchronized (this)
		{
			buffer.setLength(0);
			dateFormat.format(new Date(), buffer, dummyPosition);
			buffer.append(connectionIDString);
			buffer.append(str);

			// synchronize to ensure that the exception (if any) does
			// not get split up from the corresponding log message
			synchronized (writer)
			{
				writer.println(buffer.toString());
				if (t != null)
				{
					t.printStackTrace(writer);
				}
			}
			writer.flush();
		}
	}
}