thread safe logging in a servlet

[John Schretz]

using log4j would the following example be considered thread safe?

   
public class SubmitOrderServlet  extends HttpServlet
{   
	
	static Logger logger = Logger.getLogger(SubmitOrderServlet.class);  //is declaring this here thread safe?

	public void doGet(HttpServletRequest request,
			HttpServletResponse response)
	throws IOException, ServletException
	{ 

                                 logger.info("log something here");  //using it here


		String url = "/expressConfirm.jsp";

		RequestDispatcher dispatcher =
			getServletContext().getRequestDispatcher(url);
		dispatcher.forward(request, response);
	}
}

 

[John Schretz]

and to further explain

would i declare String realPath = getServletContext().getRealPath("/");
String fileSep = System.getProperty("file.separator");

in the class declaration or the servlet doGet method?

i think im just confusing myself

i was under the impression that nothing should be declared global in a servlet

   

      
public class SubmitOrderServlet  extends HttpServlet   
{      
       
    static Logger logger = Logger.getLogger(SubmitOrderServlet.class);  //is declaring this here thread safe?   
  
    public void doGet(HttpServletRequest request,   
            HttpServletResponse response)   
    throws IOException, ServletException   
    {    

		String realPath = getServletContext().getRealPath("/");
		String fileSep = System.getProperty("file.separator");


		if (realPath != null && (!realPath.endsWith(fileSep))){
			realPath = realPath + fileSep;
		}

		PropertyConfigurator.configure(realPath
				+ "WEB-INF/classes/log4j.properties");
  
                                 logger.info("log something here");  //using it here   
  
  
        String url = "/expressConfirm.jsp";   
  
        RequestDispatcher dispatcher =   
            getServletContext().getRequestDispatcher(url);   
        dispatcher.forward(request, response);   
    }   
} 
 

[Bear Bibeault]

Declaring the logger at class level ("global" isn't the correct term) is fine as Log4J handles the thread safety issue internally.

In general, you want to keep read/write data local to the methods.

If data needs to be shared across threads, it can safely be done as long as the threads only read the data, or if they synchronize access to read/write data.

[Duc Vo]

(1) Log4j is thread safe by design, so you don't have to worry about question 1.
(2) Log4j will search for the first log4j.properties file on the classpath to configure itself when loaded, normally it will be from WEB-INF/classes/log4j.properties. Hence, you don't have to do the code as in question 2.

Hope it help,

Duc

[John Schretz]

ok so for read write would the example below be correct?

    
public class SubmitOrderServlet  extends HttpServlet   
{      

    public void doGet(HttpServletRequest request,   
            HttpServletResponse response)   
    throws IOException, ServletException   
    {    
  
                // All kept local in method***************
                Icharge icharge = new Icharge();

       	icharge.setCardCVV2Data(cvv2);
	icharge.setCardNumber(cardNum);
	icharge.setCardExpMonth(expMonth);
	icharge.setCardExpYear(expYear);
	icharge.setCustomerFirstName(user.getBillfirstName());
	icharge.setCustomerLastName(user.getBilllastName());
	icharge.setCustomerAddress(user.getBilladdress1());
	icharge.setCustomerCity(user.getBillcity());
	icharge.setCustomerState(user.getBillstate());
	icharge.setCustomerZip(user.getBillzip());

                icharge.authorize();
  
        String url = "/expressConfirm.jsp";   
  
        RequestDispatcher dispatcher =   
            getServletContext().getRequestDispatcher(url);   
        dispatcher.forward(request, response);   
    }   
}  

[John Schretz]

Duc Vo wrote:(1) Log4j is thread safe by design, so you don't have to worry about question 1.
(2) Log4j will search for the first log4j.properties file on the classpath to configure itself when loaded, normally it will be from WEB-INF/classes/log4j.properties. Hence, you don't have to do the code as in question 2.

Hope it help,

Duc

ok but if i want log4j to log to 2 seprate log files with different names can that be done by having 2 properties files and
adding:

  
String realPath = getServletContext().getRealPath("/");   
        String fileSep = System.getProperty("file.separator");   
  
  
        if (realPath != null && (!realPath.endsWith(fileSep))){   
            realPath = realPath + fileSep;   
        }   
  
        PropertyConfigurator.configure(realPath   
                + "WEB-INF/classes/log4j.properties");   
  

thanks

[Bear Bibeault]

John Schretz wrote:ok so for read write would the example below be correct?

Yes. The variables are local to the method and the thread.

[John Schretz]

Bear Bibeault wrote:

John Schretz wrote:ok so for read write would the example below be correct?

Yes. The variables are local to the method and the thread.

Thanks again bear

[Duc Vo]

Unfortunately, it is a wrong approach for the problem. If you want to send log entries to two different files, you'll only need two appenders declared in the same log4j.properties file.

I.e. say I want to log all entries to a debug.log file, and all error entries to a error.log file, also all log entries will be sent to the CONSOLE. I'll declare my log4j.properties as below.

#CONSOLE
log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
log4j.appender.CONSOLE.layout.ConversionPattern=%-5p[%d{HH:mm:ss,SSS}][%C{1}.%M] %x - %m%n

#DEBUGFILE
log4j.appender.DEBUGFILE.layout=org.apache.log4j.PatternLayout
log4j.appender.DEBUGFILE.MaxFileSize=2048KB
log4j.appender.DEBUGFILE=org.apache.log4j.RollingFileAppender
log4j.appender.DEBUGFILE.file=/var/logs/debug.log
log4j.appender.DEBUGFILE.MaxBackupIndex=100
log4j.appender.DEBUGFILE.layout.ConversionPattern=%-5p[%d{dd/MM/yy HH:mm:ss,SSS}][%t][%C{1}.%M] %x - %m%n
log4j.appender.DEBUGFILE.Threshold=DEBUG

#ERRORFILE
log4j.appender.ERRORFILE.layout=org.apache.log4j.PatternLayout
log4j.appender.ERRORFILE.MaxFileSize=2048KB
log4j.appender.ERRORFILE=org.apache.log4j.RollingFileAppender
log4j.appender.ERRORFILE.file=/var/logs/error.log
log4j.appender.ERRORFILE.MaxBackupIndex=100
log4j.appender.ERRORFILE.layout.ConversionPattern=%-5p[%d{dd/MM/yy HH:mm:ss,SSS}][%t][%C{1}.%M] %x - %m%n
log4j.appender.ERRORFILE.Threshold=ERROR

#Mapping loggers to appenders
log4j.rootLogger=DEBUG, DEBUGFILE, ERRORFILE, CONSOLE

[John Schretz]

Duc Vo wrote:Unfortunately, it is a wrong approach for the problem. If you want to send log entries to two different files, you'll only need two appenders declared in the same log4j.properties file.

I.e. say I want to log all entries to a debug.log file, and all error entries to a error.log file, also all log entries will be sent to the CONSOLE. I'll declare my log4j.properties as below.

#CONSOLE
log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
log4j.appender.CONSOLE.layout.ConversionPattern=%-5p[%d{HH:mm:ss,SSS}][%C{1}.%M] %x - %m%n

#DEBUGFILE
log4j.appender.DEBUGFILE.layout=org.apache.log4j.PatternLayout
log4j.appender.DEBUGFILE.MaxFileSize=2048KB
log4j.appender.DEBUGFILE=org.apache.log4j.RollingFileAppender
log4j.appender.DEBUGFILE.file=/var/logs/debug.log
log4j.appender.DEBUGFILE.MaxBackupIndex=100
log4j.appender.DEBUGFILE.layout.ConversionPattern=%-5p[%d{dd/MM/yy HH:mm:ss,SSS}][%t][%C{1}.%M] %x - %m%n
log4j.appender.DEBUGFILE.Threshold=DEBUG

#ERRORFILE
log4j.appender.ERRORFILE.layout=org.apache.log4j.PatternLayout
log4j.appender.ERRORFILE.MaxFileSize=2048KB
log4j.appender.ERRORFILE=org.apache.log4j.RollingFileAppender
log4j.appender.ERRORFILE.file=/var/logs/error.log
log4j.appender.ERRORFILE.MaxBackupIndex=100
log4j.appender.ERRORFILE.layout.ConversionPattern=%-5p[%d{dd/MM/yy HH:mm:ss,SSS}][%t][%C{1}.%M] %x - %m%n
log4j.appender.ERRORFILE.Threshold=ERROR

#Mapping loggers to appenders
log4j.rootLogger=DEBUG, DEBUGFILE, ERRORFILE, CONSOLE

what if i wanted to specify a file eg.
'SysLog.txt'

all i want to use is logger.info()
but i want to be able to log to 2 custom files

'SysLog1.txt'
'SysLog2.txt'

below is my config file

   
# An log4j configuration file that outputs both to System.out
# and a file named 'SysLog.txt'.

# The root logger uses the appenders called A1 and A2. Since no level
# is specified, note the empty string between the comma (",") and the
# equals sign ("="), the level of the root logger remains
# untouched. Log4j always initializes the level for the root logger to
# DEBUG. The root logger is the only logger that has a default
# level. By default, all other loggers do not have an assigned level,
# such that they inherit their level instead.

log4j.rootLogger=, A1, A2

# A1 is set to be ConsoleAppender sending its output to System.out
log4j.appender.A1=org.apache.log4j.ConsoleAppender


# A1 uses PatternLayout.
log4j.appender.A1.layout=org.apache.log4j.PatternLayout

log4j.appender.A1.layout.ConversionPattern=%d{dd MMM yyyy HH:mm:ss,SSS}%1x- %m%n

# Appender A2 writes to the file "SysLog.txt".
log4j.appender.A2=org.apache.log4j.RollingFileAppender
log4j.appender.A2.MaxFileSize=30MB
log4j.appender.A2.MaxBackupIndex=5
log4j.appender.A2.File=${catalina.home}/logs/SysLog.txt

# Truncate 'SysLog.txt' if it aleady exists.
log4j.appender.A2.Append=true

# Appender A2 uses the PatternLayout.
log4j.appender.A2.layout=org.apache.log4j.PatternLayout
log4j.appender.A2.layout.ConversionPattern=%d{dd MMM yyyy HH:mm:ss,SSS}%1x- %m%n


 

[Duc Vo]

John,

The answer is actually in my previous post.

Just create A3 which writes to SysLog2.txt, sets the Threshold to INFO, then configure the logger to use A3 as well i.e.
log4j.rootLogger = , A1, A2, A3

[John Schretz]

Sorry for the late response. Thanks that makes sense, the first time i read it i maut have read it too fast and overlooked the actual answer lol
thanks again
john