Logging and Determining a Logged Message
This section introduce you about Java logging and how to
use the logger in Java program to log the error and messages into the log file. Explanation of java logging is
explained in the given example program. This program will help you understand the java logging and
its implementation in the java program.
Java provides logging APIs like: Logger, Level, Handler etc. for
implementing logging features in your java application. It is a part of
J2SE (Java 2 Standard Edition). To create java logging program you need a Logger object. The Logger object contains log messages.
Logger has one or more handler that performs log records. Java logging
provides a way to contain multiple types of message like: warning,
info, severe
etc. for an application. These information or messages can be used for many
purposes but it is specially used for debugging, troubleshooting and auditing.
The first program simply create a log file and shows
log message for the warning, info and servere
and another checked the logging
message. This program creates a log file that contains multiple
information.
Code Descriptions:
FileHandler(String file_name):
This is the constructor of FileHandler class. FileHandler class extends the
StreamHandler. This is the class of java.uti.logging package. The above
constructor constructs the FileHandler with given string as file name.
Logger:
This is the constructor of Logger class. The logger class extends the
Object. IThis is the class of java.util.logging package. Logger constructor used
for constructing a logger. A logger object contains a log message to the system
or application component. The logger object called by the getLogger method and
returns a suitable maintain logger.
getLogger(String log_name):
You can find or construct a logger with the help of above method. It takes
string types value that can be used for a named subsystem.
addHandler:
It can be used for adding a log handler to get logging message which is
maintaining in the warning, info and severe.
warning(String war_message):
This method used for showing the log WARNING message. The given message
shows to all output handler objects when the logger is enabled at the time of
warning message level. It takes string type value for the warning message.
info(String info_message):
It works same as warning method but it shows log INFO message.
servere(String ser_message):
It also works same as like: warning and info method but it shows log SERVERE
message.
Here is the code of "QuintLog.java":
import java.io.*;
import java.util.logging.*;
public class QuintLog{
public static void main(String[] args) {
try{
FileHandler hand = new FileHandler("vk.log");
Logger log = Logger.getLogger("log_file");
log.addHandler(hand);
log.warning("Doing carefully!");
log.info("Doing something ...");
log.severe("Doing strictily ");
System.out.println(log.getName());
}
catch(IOException e){}
}
}
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Program Descriptions:
This program check logger object. If given instruction
is certify then shows finest message like: 'Display a finest message' otherwise
no any message appear to here.
Code Descriptions:
isLoggable(Level level):
The above method is a Boolean type than returns true or false. It checks the
given message is actually logged by this logger that means method is returned
true.
finest(String fi_message):
The above method is used to represent the Log FINEST message. This message
shows to all output handler objects when the logger is enabled at the time of
finest message level . It takes string type value for message.
Here is the code of "CheckLogMessage.java":
import java.io.*;
import java.util.logging.*;
public class CheckLogMessage{
public static void main(String[] args) {
Logger log = Logger.getLogger("log_file");
if(log.isLoggable(Level.OFF)){
log.finest("Display a finest message");
}
}
}
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Download this example.
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