Module: SLF4J

Includes:
SLF4JBase
Defined in:
lib/slf4j.rb

Overview

Wrapper and core Logger compatible adapter for the SLF4J logging interface.

Usage

require 'slf4j'

log = SLF4J[ "my.app.logger" ]
log.info "Hello World!"

Adapters

All of the following output adapters are available via require:

require 'slf4j/jcl'       # Output to Jakarta Commons Logging
require 'slf4j/jdk14'     # JDK java.util.logging 
require 'slf4j/log4j12'   # Log4j (provided elsewhere)
require 'slf4j/nop'       # NOP null logger (provided)
require 'slf4j/simple'    # Simple logger (provided)

The first loaded output adapter wins (as with mulitple adapters on the classpath). A warning will be logged to “slf4j” if an attempt is made to require a second output adapter.

And the following input adapters will intercept JCL, java.util.logging (jdk14), or log4j log output and direct it through SLF4J:

require 'slf4j/jcl-over-slf4j'   # Route Jakarta Commons Logging to SLF4J
require 'slf4j/jul-to-slf4j'     # JDK java.util.logging to SLF4J
require 'slf4j/log4j-over-slf4j' # Log4j to SLF4J

Multiple input adapters may be require’d. However, a RuntimeError will be raised in the attempt to require both an output adapter and input adapter from/to the same interface, for example ‘slf4j/jcl-over-slf4j’ and ‘slf4j/jcl’, which would otherwise cause a circular logging loop (and stack overflow.)

Adapter names match the corresponding SLF4J jars.

Defined Under Namespace

Classes: Logger

Constant Summary collapse

LEVELS =

SLF4J severity levels

%w{ trace debug info warn error }
@@api_loader = 
org.slf4j.ILoggerFactory.java_class.class_loader
@@loaded = 
{}
@@output_name = 
nil

Constants included from SLF4JBase

SLF4JBase::ADAPTERS, SLF4JBase::SLF4J_DIR, SLF4JBase::SLF4J_VERSION, SLF4JBase::VERSION

Class Method Summary collapse

Class Method Details

.[](name) ⇒ Object

Synonym for logger( name )



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# File 'lib/slf4j.rb', line 194

def self.[]( name )
  Logger.new( name )
end

.linked_factory ⇒ Object

The ILoggerFactory instance if an output adapter jas been loaded



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# File 'lib/slf4j.rb', line 199

def self.linked_factory
   org.slf4j.LoggerFactory.getILoggerFactory
end

.logger(name = self.class.name) ⇒ Object

Get Logger by name



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# File 'lib/slf4j.rb', line 188

def logger( name = self.class.name ) 
  Logger.new( name )
end

.output_name ⇒ Object

Output adapter name if one has been added, or nil.



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# File 'lib/slf4j.rb', line 124

def self.output_name
  @@output_name
end

.require_adapter(name) ⇒ Object

Require an adapter by name (add the jar to classpath) This is normally done via require ‘slf4j/name’



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# File 'lib/slf4j.rb', line 73

def self.require_adapter( name ) 
  row = ADAPTERS.assoc( name )
  if row 
    name,ban = row
    output = false
  else
    row = ADAPTERS.rassoc( name )
    ban,name = row
    output = true
  end
 
  if @@loaded[ ban ]
    raise "Illegal attempt to load '#{name}' when '#{ban}' is loaded."
  end

  if output 
    if ! @@output_name.nil? && name != @@output_name
      logger("slf4j").warn do
        "Ignoring attempt to load #{name} after #{@@output_name} already loaded." 
      end
      return
    end
    if java.lang.Thread::current_thread.context_class_loader != @@api_loader
      $stderr.puts( "WARNING: Attempting to load #{name} in child class" + 
                    " loader of slf4j-api.jar loader." )
    end
    require_jar( 'slf4j-' + name )
    @@output_name = name
  else
    require_jar( name )
  end

  # Special case, requires explicit 'install'
  if name == 'jul-to-slf4j' 
    org.slf4j.bridge.SLF4JBridgeHandler.install
  end

  @@loaded[ name ] = true
end

.require_jar(name) ⇒ Object

:nodoc:



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# File 'lib/slf4j.rb', line 113

def self.require_jar( name ) # :nodoc:
  require File.join( SLF4J_DIR, "#{name}-#{ SLF4J_VERSION }.jar" )
end