Module: Jinx::Importer

Defined in:
lib/jinx/importer.rb

Overview

Importer extends a module with Java class import support. Importer is an aspect of a Metadata module. Including Metadata in an application domain module extends that module with Importer capability.

The Importer module imports a Java class or interface on demand by referencing the class name in the context of the module. The imported class Metadata is introspected.

Import on demand is induced by a reference to the class. The family example illustrates a domain package extended with metadata capability. The first non-definition reference to Family::Parent imports the Java class family.Parent into the JRuby class wrapper Family and introspects the Java property meta-data.

Instance Method Summary collapse

Instance Method Details

#add_metadata(klass) ⇒ Object (private)

Introspects the given class meta-data.

Parameters:

  • klass (Class) —

    the Java class or interface to introspect



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# File 'lib/jinx/importer.rb', line 193

def add_metadata(klass)
  logger.debug("Adding #{self}::#{klass.qp} metadata...")
  # Mark the class as introspected. Do this first to preclude a recursive loop back
  # into this method when the references are introspected below.
  @introspected << klass
  # Add the superclass meta-data if necessary.
  if Class === klass then
    sc = klass.superclass
    unless @introspected.include?(sc) or sc == Java::java.lang.Object then
      add_metadata(sc)
    end
  end
  # Include this resource module into the class.
  unless klass < self then
    m = self
    klass.class_eval { include m }
  end
  # Add introspection capability to the class.
  md_mod = @metadata_module || Metadata
  
  logger.debug { "Extending #{self}::#{klass.qp} with #{md_mod.name}..." }
  klass.extend(md_mod)
  
  # Introspect the Java properties.
  introspect(klass)
  klass.add_attribute_value_initializer if Class === klass
  # Set the class domain module.
  klass.domain_module = self
  # Add referenced domain class metadata as necessary.
  mod = klass.parent_module
  klass.each_property do |prop|
    ref = prop.type
    if ref.nil? then raise MetadataError.new("#{self} #{prop} domain type is unknown.") end
    unless @introspected.include?(ref) or ref.parent_module != mod then
      logger.debug { "Introspecting #{qp} #{prop} reference #{ref.qp}..." }
      add_metadata(ref)
    end
  end
  logger.debug("#{self}::#{klass.qp} metadata added.")
end

#configure_importer ⇒ Object (private)

Initializes this importer on demand. This method is called the first time a class is referenced.



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# File 'lib/jinx/importer.rb', line 93

def configure_importer
  # The default package conforms to the JRuby convention for mapping a package name
  # to a module name.
  @packages ||= [name.split('::').map { |n| n.downcase }.join('.')]
  @packages.each do |pkg|
    begin
      eval "java_package Java::#{pkg}"
    rescue Exception => e
      raise ArgumentError.new("#{self} Java package #{pkg} not found - #{$!}")
    end
  end
  # The introspected classes.
  @introspected = Set.new
end

#const_missing(sym) ⇒ Class

Imports a Java class constant on demand. If the class does not already include this module’s mixin, then the mixin is included in the class.

Parameters:

Returns:

  • (Class) —

    the imported class

Raises:

  • (NameError) —

    if the symbol is not an importable Java class



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# File 'lib/jinx/importer.rb', line 34

def const_missing(sym)
  # Load the class definitions in the source directory, if necessary.
  # If a load is performed as a result of referencing the given symbol,
  # then dereference the class constant again after the load, since the class
  # might have been loaded or referenced during the load.
  unless defined? @introspected then
    configure_importer
    load_definitions
    return const_get(sym)
  end
  
  # Append the symbol to the package to make the Java class name.
  logger.debug { "Detecting whether #{sym} is a #{self} Java class..." }
  klass = @packages.detect_value do |pkg|
    begin
       java_import "#{pkg}.#{sym}"
    rescue NameError
      nil
    end
  end
  if klass.nil? then
    # Not a Java class; print a log message and pass along the error.
    logger.debug { "#{sym} is not recognized as a #{self} Java class." }
    super
  end
  
  # Introspect the Java class meta-data, if necessary.
  unless @introspected.include?(klass) then
    add_metadata(klass)
    # Print the class meta-data.
    logger.info(klass.pp_s)
  end
  
  klass
end

#definitions(*directories) ⇒ Object (private)

Parameters:

  • directories (<String>) —

    the Ruby class definitions directories



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# File 'lib/jinx/importer.rb', line 121

def definitions(*directories)
  @definitions = directories
end

#introspect(klass) ⇒ Object (private)

Introspects the given class.

Parameters:

  • the (Class) —

    domain class to introspect



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# File 'lib/jinx/importer.rb', line 237

def introspect(klass)
  klass.introspect
end

#load_definitions ⇒ Object (private) 



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# File 'lib/jinx/importer.rb', line 125

def load_definitions
  return if @definitions.nil_or_empty?
  # Load the class definitions in the source directories.
  @definitions.each { |dir| load_dir(File.expand_path(dir)) }
  # Print each introspected class's content.
  @introspected.sort { |k1, k2| k1.name <=> k2.name }.each { |klass| logger.info(klass.pp_s) }
  true
end

#load_dir(dir) ⇒ Object (private)

Loads the Ruby source files in the given directory.

Parameters:

  • dir (String) —

    the source directory



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# File 'lib/jinx/importer.rb', line 137

def load_dir(dir)
  logger.debug { "Loading the class definitions in #{dir}..." }
  # Import the classes.
  srcs = sources(dir)
  # Introspect and load the classes in reverse class order, i.e. superclass before subclass.
  klasses = srcs.keys.transitive_closure { |k| [k.superclass] }.select { |k| srcs[k] }.reverse
  # Introspect the classes if necessary.
  klasses.each { |klass| add_metadata(klass) unless @introspected.include?(klass) }
  # Load the classes.
  klasses.each do |klass|
    file = srcs[klass]
    logger.debug { "Loading #{klass.qp} definition #{file}..." }
    require file
    logger.debug { "Loaded #{klass.qp} definition #{file}." }
  end
  logger.debug { "Loaded the class definitions in #{dir}." }
end

#module_for_name(name) ⇒ Module

Returns the corresponding module.

Parameters:

  • the (String) —

    module name to resolve in the context of this module

Returns:

  • (Module) —

    the corresponding module

Raises:

  • (NameError) —

    if the name cannot be resolved



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# File 'lib/jinx/importer.rb', line 73

def module_for_name(name)
  begin
    # Incrementally resolve the module.
    name.split('::').inject(self) { |ctxt, mod| ctxt.const_get(mod) }
  rescue NameError
    # If the application domain module set the parent module i.v.. then continue
    # the look-up in that parent importer.
    raise unless @parent_importer
    mod = @parent_importer.module_for_name(name)
    if mod then
      logger.debug { "Module #{name} found in #{qp} parent module #{@parent_importer}." }
    end
    mod
  end
end

#packages(*names) ⇒ Object (private) Also known as: package

Sets the package names. The default package conforms to the JRuby convention for mapping a package name to a module name, e.g. the MyApp::Domain default package is myapp.domain. Clients set the package if it differs from the default.

Parameters:

  • name (<String>) —

    the package names



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# File 'lib/jinx/importer.rb', line 113

def packages(*names)
  @packages = names
end

#resolve_class(name, package = nil) ⇒ Class? (private)

Returns the Resource class imported into this module, or nil if the class cannot be resolved.

Parameters:

  • name (String) —

    the demodulized class name

  • package (String) (defaults to: nil) —

    the Java package, or nil for all packages

Returns:

  • (Class, nil) —

    the Resource class imported into this module, or nil if the class cannot be resolved



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# File 'lib/jinx/importer.rb', line 172

def resolve_class(name, package=nil)
  if const_defined?(name) then
    return const_get(name)
  end
  if package.nil? then
    return @packages.detect_value { |pkg| resolve_class(name, pkg) }
  end
  # Append the class name to the package to make the Java class name.
  full_name = "#{package}.#{name}"
  # If the class is already imported, then java_import returns nil. In that case,
  # evaluate the Java class.
  begin
    java_import(full_name)
  rescue
    module_eval("Java::#{full_name}") rescue nil
  end
end

#shims(*classes) ⇒ Object

Declares that the given Resource classes will be dynamically modified. This method introspects the classes, if necessary.

Parameters:

  • classes (<Class>) —

    the classes to augment



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# File 'lib/jinx/importer.rb', line 23

def shims(*classes)
  # Nothing to do, since all this method does is ensure that the arguments are
  # introspected when they are referenced.
end

#sources(dir) ⇒ {Class => String} (private)

Returns the source class => file hash.

Parameters:

  • dir (String) —

    the source directory

Returns:

  • ({Class => String}) —

    the source class => file hash



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# File 'lib/jinx/importer.rb', line 157

def sources(dir)
  # the domain class definitions
  files = Dir.glob(File.join(dir, "*.rb"))
  # Infer each class symbol from the file base name.
  # Ignore files which do not resolve to a class.
  files.to_compact_hash do |file|
    name = File.basename(file, ".rb").camelize
    resolve_class(name)
  end.invert
end