Package com.jcabi.log

Class Logger

java.lang.Object

com.jcabi.log.Logger

public final class Logger
extends Object

Universal logger, and adapter between your app and SLF4J API.

Instead of relying on some logging engine you can use this class, which transforms all messages to SLF4J. This approach gives you a perfect decoupling of business logic and logging mechanism. All methods in the class are called statically, without the necessity to instantiate the class.

Use it like this in any class, and in any package:

 package com.example.XXX;
 import com.jcabi.log.Logger;
 public class MyClass {
   public void foo(Integer num) {
     Logger.info(this, "foo(%d) just called", num);
   }
 }

Or statically (pay attention to MyClass.class):

 public class MyClass {
   public static void foo(Integer num) {
     Logger.info(MyClass.class, "foo(%d) just called", num);
   }
 }

Exact binding between SLF4J and logging facility has to be specified in pom.xml of your project (or in classpath directly).

For performance reasons in most cases before sending a TRACE or DEBUG log message you may check whether this logging level is enabled in the project, e.g.:

 //...
 if (Logger.isTraceEnabled(this)) {
   Logger.trace(this, "#foo() called");
 }
 //...

There is only one reason to do so - if you want to save time spent on preparing of the arguments. By default, such a call is made inside every method of Logger class.

Since:

0.1

Method Summary

Modifier and Type	Method	Description
static void	debug(Object source, String msg)	Protocol one message, with DEBUG priority level.
static void	debug(Object source, String msg, Object... args)	Protocol one message, with DEBUG priority level.
static void	debugForced(Object source, String msg, Object... args)	Protocol one message, with DEBUG priority level without internal checking whether DEBUG level is enabled.
static void	error(Object source, String msg)	Protocol one message, with ERROR priority level.
static void	error(Object source, String msg, Object... args)	Protocol one message, with ERROR priority level.
static String	format(String fmt, Object... args)	Format one string.
static void	info(Object source, String msg)	Protocol one message, with INFO priority level.
static void	info(Object source, String msg, Object... args)	Protocol one message, with INFO priority level.
static void	infoForced(Object source, String msg, Object... args)	Protocol one message, with INFO priority level without internal checking whether INFO level is enabled.
static boolean	isDebugEnabled(Object source)	Validates whether DEBUG priority level is enabled for this particular logger.
static boolean	isEnabled(Level level, Object source)	Is the given logging level enabled?
static boolean	isInfoEnabled(Object source)	Validates whether INFO priority level is enabled for this particular logger.
static boolean	isTraceEnabled(Object source)	Validates whether TRACE priority level is enabled for this particular logger.
static boolean	isWarnEnabled(Object source)	Validates whether INFO priority level is enabled for this particular logger.
static void	log(Level level, Object source, String msg, Object... args)	Log one line using the logging level specified.
static OutputStream	stream(Level level, Object source)	Returns an OutputStream, which converts all incoming data into logging lines (separated by \x0A in UTF-8).
static void	trace(Object source, String msg)	Protocol one message, with TRACE priority level.
static void	trace(Object source, String msg, Object... args)	Protocol one message, with TRACE priority level.
static void	traceForced(Object source, String msg, Object... args)	Protocol one message, with TRACE priority level without internal checking whether TRACE level is enabled.
static void	warn(Object source, String msg)	Protocol one message, with WARN priority level.
static void	warn(Object source, String msg, Object... args)	Protocol one message, with WARN priority level.
static void	warnForced(Object source, String msg, Object... args)	Protocol one message, with WARN priority level without internal checking whether WARN level is enabled.
static com.jcabi.log.SupplierLogger	withSupplier()	Log messages constructed from Suppliers.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

format

public static String format(String fmt,
                            Object... args)

Format one string.

Parameters:

fmt - The format

args - List of arbitrary arguments

Returns:

Formatted string

trace

public static void trace(Object source,
                         String msg)

Protocol one message, with TRACE priority level.

Parameters:

source - The source of the logging operation

msg - The text message to be logged

Since:

0.7.11

trace

public static void trace(Object source,
                         String msg,
                         Object... args)

Protocol one message, with TRACE priority level.

Parameters:

source - The source of the logging operation

msg - The text message to be logged, with meta-tags

args - List of arguments

traceForced

public static void traceForced(Object source,
                               String msg,
                               Object... args)

Protocol one message, with TRACE priority level without internal checking whether TRACE level is enabled.

Parameters:

source - The source of the logging operation

msg - The text message to be logged, with meta-tags

args - List of arguments

debug

public static void debug(Object source,
                         String msg)

Protocol one message, with DEBUG priority level.

Parameters:

source - The source of the logging operation

msg - The text message to be logged, with meta-tags

Since:

0.7.11

debug

public static void debug(Object source,
                         String msg,
                         Object... args)

Protocol one message, with DEBUG priority level.

Parameters:

source - The source of the logging operation

msg - The text message to be logged, with meta-tags

args - List of arguments

debugForced

public static void debugForced(Object source,
                               String msg,
                               Object... args)

Protocol one message, with DEBUG priority level without internal checking whether DEBUG level is enabled.

Parameters:

source - The source of the logging operation

msg - The text message to be logged, with meta-tags

args - List of arguments

info

public static void info(Object source,
                        String msg)

Protocol one message, with INFO priority level.

Parameters:

source - The source of the logging operation

msg - The text message to be logged

Since:

0.7.11

info

public static void info(Object source,
                        String msg,
                        Object... args)

Protocol one message, with INFO priority level.

Parameters:

source - The source of the logging operation

msg - The text message to be logged, with meta-tags

args - List of arguments

infoForced

public static void infoForced(Object source,
                              String msg,
                              Object... args)

Protocol one message, with INFO priority level without internal checking whether INFO level is enabled.

Parameters:

source - The source of the logging operation

msg - The text message to be logged, with meta-tags

args - List of arguments

warn

public static void warn(Object source,
                        String msg)

Protocol one message, with WARN priority level.

Parameters:

source - The source of the logging operation

msg - The text message to be logged

Since:

0.7.11

warn

public static void warn(Object source,
                        String msg,
                        Object... args)

Protocol one message, with WARN priority level.

Parameters:

source - The source of the logging operation

msg - The text message to be logged, with meta-tags

args - List of arguments

warnForced

public static void warnForced(Object source,
                              String msg,
                              Object... args)

Protocol one message, with WARN priority level without internal checking whether WARN level is enabled.

Parameters:

source - The source of the logging operation

msg - The text message to be logged, with meta-tags

args - List of arguments

error

public static void error(Object source,
                         String msg)

Protocol one message, with ERROR priority level.

Parameters:

source - The source of the logging operation

msg - The text message to be logged

Since:

0.7.11

error

public static void error(Object source,
                         String msg,
                         Object... args)

Protocol one message, with ERROR priority level.

Parameters:

source - The source of the logging operation

msg - The text message to be logged, with meta-tags

args - List of arguments

isTraceEnabled

public static boolean isTraceEnabled(Object source)

Validates whether TRACE priority level is enabled for this particular logger.

Parameters:

source - The source of the logging operation

Returns:

Is it enabled?

isDebugEnabled

public static boolean isDebugEnabled(Object source)

Validates whether DEBUG priority level is enabled for this particular logger.

Parameters:

source - The source of the logging operation

Returns:

Is it enabled?

isInfoEnabled

public static boolean isInfoEnabled(Object source)

Validates whether INFO priority level is enabled for this particular logger.

Parameters:

source - The source of the logging operation

Returns:

Is it enabled?

Since:

0.5

isWarnEnabled

public static boolean isWarnEnabled(Object source)

Validates whether INFO priority level is enabled for this particular logger.

Parameters:

source - The source of the logging operation

Returns:

Is it enabled?

Since:

0.5

isEnabled

public static boolean isEnabled(Level level,
                                Object source)

Is the given logging level enabled?

Parameters:

level - The level of logging

source - The source of the logging operation

Returns:

Is it enabled?

Since:

0.13

log

public static void log(Level level,
                       Object source,
                       String msg,
                       Object... args)

Log one line using the logging level specified.

Parameters:

level - The level of logging

source - The source of the logging operation

msg - The text message to be logged

args - Optional arguments for string formatting

Since:

0.8

Suppressed Checkstyle violations:

ParameterNumber (4 lines)

stream

public static OutputStream stream(Level level,
                                  Object source)

Returns an OutputStream, which converts all incoming data into logging lines (separated by \x0A in UTF-8).

Parameters:

level - The level of logging

source - The source of the logging operation

Returns:

Output stream directly pointed to the logging facility

Since:

0.8

See Also:

some discussion

Suppressed Checkstyle violations:

MagicNumberCheck (20 lines)

withSupplier

public static com.jcabi.log.SupplierLogger withSupplier()

Log messages constructed from Suppliers. It is more efficient to use method referencing because the method won't be called unless the specified logging level is enabled. This saves you the effort of having to check if the level is enabled before calling the logging method. E.g.

     if (Logger.isDebugEnabled(this)) {
         Logger.debug(this, "Some %s", calculate());
     }
 

turns into

     Logger.withSupplier().debug(this, "Some %s", this::calculate());
 

and the calculate() method won't be called unless the debug level is active.

Returns:

Object containing methods for logging with Supplier-constructed messages