The Layout class provides methods for formatting log events into a string representation. Layouts are used by Appenders to format log events before writing them to the logging destination.
All other Layouts inherit from this class which provides stub methods. Each subclass should provide a format method. A layout can be used by more than one Appender so all the methods need to be thread safe.
Creates a new layout that will format objects as strings using the given :format_as style. This can be one of :string, :inspect, or :yaml. These formatting commands map to the following object methods:
:string => to_s
:inspect => inspect
:yaml => to_yaml
:json => MultiJson.encode(obj)
If the format is not specified then the global object format is used (see Logging#format_as). If the global object format is not specified then :string is used.
# File lib/logging/layout.rb, line 31 def initialize( opts = {} ) ::Logging.init unless ::Logging.initialized? default = ::Logging.const_defined?('OBJ_FORMAT') ? ::Logging::OBJ_FORMAT : nil f = opts.getopt(:format_as, default) f = f.intern if f.instance_of? String @obj_format = case f when :inspect, :yaml, :json; f else :string end b = opts.getopt(:backtrace, ::Logging.backtrace) @backtrace = case b when :on, 'on', true; true when :off, 'off', false; false else raise ArgumentError, "backtrace must be true or false" end end
Returns a string representation of the given logging event. It is up to subclasses to implement this method.
# File lib/logging/layout.rb, line 59 def format( event ) nil end
Return a string representation of the given object. Depending upon the configuration of the logger system the format will be an inspect based representation or a yaml based representation.
# File lib/logging/layout.rb, line 83 def format_obj( obj ) case obj when String; obj when Exception str = "<#{obj.class.name}> #{obj.message}" if @backtrace && !obj.backtrace.nil? str << "\n\t" << obj.backtrace.join("\n\t") end str when nil; "<#{obj.class.name}> nil" else str = "<#{obj.class.name}> " str << case @obj_format when :inspect; obj.inspect when :yaml; try_yaml(obj) when :json; try_json(obj) else obj.to_s end str end end
Returns a header string to be used at the beginning of a logging appender.
# File lib/logging/layout.rb, line 67 def header( ) '' end
Attempt to format the given object as a JSON string, but fall back to inspect formatting if JSON encoding fails.
obj - The Object to format.
Returns a String representation of the object.
# File lib/logging/layout.rb, line 124 def try_json( obj ) MultiJson.encode(obj) rescue StandardError obj.inspect end
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