java_main_utils.rb

# frozen_string_literal: true

# Cloud Foundry Java Buildpack
# Copyright 2013-2020 the original author or authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

require 'java_buildpack/util/configuration_utils'
require 'java_buildpack/util'
require 'java_buildpack/util/properties'

module JavaBuildpack
  module Util

    # Java Main application utilities.
    class JavaMainUtils

      private_class_method :new

      class << self

        # Returns the Java main class name for the Java main configuration and given application directory or +nil+ if
        # this is not a Java main application.
        #
        # @param [JavaBuildpack::Component::Application] application the application
        # @param [Hash] configuration the Java main configuration or +nil+ if this is not provided
        # @return [String, nil] the Java main class name or +nil+ if there is no Java main class name
        def main_class(application, configuration = nil)
          config = configuration || JavaBuildpack::Util::ConfigurationUtils.load('java_main')
          config[MAIN_CLASS_PROPERTY] || manifest(application)[MANIFEST_PROPERTY]
        end

        # Return the manifest properties of the given application.
        #
        # @param [JavaBuildpack::Application::Application] application the application
        # @return [Properties] the properties from the application's manifest (if any)
        def manifest(application)
          manifest_file = application.root + 'META-INF/MANIFEST.MF'
          manifest_file = nil unless manifest_file.exist?
          JavaBuildpack::Util::Properties.new(manifest_file)
        end

        MAIN_CLASS_PROPERTY = 'java_main_class'

        MANIFEST_PROPERTY = 'Main-Class'

        private_constant :MAIN_CLASS_PROPERTY, :MANIFEST_PROPERTY

      end

    end

  end
end