You need to read an application server log file , but you do not know where it is !!!

Background:

One Friday at around 10.30 at night , a very close friend of mine called me on my mobile and told me that he is facing a problem.He is working on a maintenance project which runs on a server , of which the log file location is unknown.He does not have the documents or time to do RnD on searching the log files also.But he needs to have a look at the log immediately !! There is a severe bug he needs to fix within few hours , otherwise there will be some sort of escalations.

Initially I suggested him to read the server related docs (which I myself have read on rare occasions !! ) and do some Googling on this .In reply he told me that he has already done that and still he is stuck .He needs a quick simple working solution for the time being !!

Problem Description:

To get the log file of a server at a known directory , irrespective of its default location.

Solution (or patch ?? ):

What I suggested for a quick fix is to use the System.setErr() and System.setOut() method of java, to point the console output to a custom location.Both methods should have a PrintStream object as argument, which will point to a specific file provided by you .In that case all the prints or exceptions will be stored in that specific location.

Sample code:

package com.ayan.util;

import java.io.File;
import java.io.FileOutputStream;
import java.io.PrintStream;

/**
* This class is an utility class containing a method to change the console
* output location as per the choice of the user .
*
* To use this util file ,the User just needs to add one liner code like :
* ConsoleUtil.setSystemOutPutLocation(outFileLocation,isError);
*
*
* @author ayandutta
*
*/
public class ConsoleUtil
{
public static String NORMAL_OUTPUT_FILE_NAME = "SysoutFile.txt";
public static String ERROR_FILE_NAME = "SysError.txt";
public static String OUTPUT_DIRECTORY = "c:" ;

public static String NORMAL_OUTPUT_FILE_LOCATION = OUTPUT_DIRECTORY + File.separator + File.separator+NORMAL_OUTPUT_FILE_NAME;
public static String ERROR_FILE_LOCATION =OUTPUT_DIRECTORY + File.separator + File.separator+ERROR_FILE_NAME;

/**
* This method sets the console out put location file.
* It works for sysout or syserror
* @param outFileLocation
* @param isError
*/
public static void setSystemOutPutLocation(String outFileLocation,boolean isError)
{
try
{
FileOutputStream outFileStr = new FileOutputStream(outFileLocation, true);
PrintStream outFilePrintStream = new PrintStream(outFileStr);
if(isError)
{
System.setErr(outFilePrintStream);
//System.out.println(" Error file is changed to : " +outFileLocation);
}
else
{
System.setOut(outFilePrintStream);
//System.out.println(" Output file is changed to : " +outFileLocation);
}
}
catch (Exception e)
{
System.out.println("Exception inside method setSystemOutPutLocation(),printing stack trace...");
e.printStackTrace();
}
}

public static void main(String[] args)
{


//Normal Sysouts and Syserrors Before console location is changed
System.out.println("Text for normal out put before file configuration");
System.err.println("Text error out put before file configuration");

//Here is the code where Sysouts and Syserrors console location is changed
setSystemOutPutLocation(NORMAL_OUTPUT_FILE_LOCATION, false);
setSystemOutPutLocation(ERROR_FILE_LOCATION, true);

//Normal Sysouts and Syserrors after console location is changed
System.out.println("Text for normal out put after file configuration");
System.err.println("Text error out put after file configuration");


//By force generating an Exception
generateException();
}

/**
* Just a method to create an exception by force
*/
public static void generateException()
{
try
{
String nullStr = null;
System.out.println(nullStr.length());
}
catch (Exception e)
{
System.out.println("Exception inside method generateException(),printing stack trace...");
e.printStackTrace();
}
}

/**
* Just a method to create an exception by force
*/
public static void printExecutionLocation()
{
System.out.println(System.getProperty("user.dir"));
}

public static void printAllEnvironmentInfo()
{
System.out.println(System.getProperties());
}
}

How to use this program :

Now invoke setSystemOutPutLocation(NORMAL_OUTPUT_FILE_LOCATION, false) and setSystemOutPutLocation(ERROR_FILE_LOCATION, true) from any of the classes of your running application .The log file will be generated on the location provided.

Disclaimer:

The solution (I would rather mention it as a patch ) that I provided at that point of time is just for solving the log file related issue quickly .It is not at all a complete solution .