Helper behaviors

This change adds some helper behaviors that can be used by downstream
components.  Specifically, this adds the ability to execute a block
with JAVA_HOME set, and makes the copy_resources and download_jar
methods a bit more robust.

lib/java_buildpack/application/java_home.rb

@@ -43,6 +43,19 @@ def as_env_var
       "JAVA_HOME=#{self}"
     end
 
+    # Execute a block with the +JAVA_HOME+ environment variable set
+    #
+    # @yield yields to block with the +JAVA_HOME+ environment variable set
+    def do_with
+      previous_value = ENV['JAVA_HOME']
+      begin
+        ENV['JAVA_HOME'] = to_s
+        yield
+      ensure
+        ENV['JAVA_HOME'] = previous_value
+      end
+    end
+
   end
 
 end

lib/java_buildpack/base_component.rb

@@ -79,10 +79,12 @@ def release
 
     protected
 
-    # Copy resources from a components resources directory to its +home+ directory
-    def copy_resources
+    # Copy resources from a components resources directory to a directory
+    #
+    # @param [Pathname] target_directory the directory to copy to.  Default to a component's +home+
+    def copy_resources(target_directory = home)
       resources = Pathname.new(File.expand_path('../../../resources', __FILE__)) + @parsable_component_name
-      FileUtils.cp_r((resources.to_s + '/.'), home) if resources.exist?
+      FileUtils.cp_r((resources.to_s + '/.'), target_directory) if resources.exist?
     end
 
     # Downloads an item with the given name and version from the given URI, then yields the resultant file to the given
@@ -111,7 +113,8 @@ def download(version, uri, description = @component_name, &block)
     #                                  +@lib_directory+
     # @param [String] description an optional description for the download.  Defaults to +@component_name+.
     def download_jar(version, uri, jar_name, target_directory = @lib_directory, description = @component_name)
-      download(version, uri, description) { |file| FileUtils.cp file.path, File.join(target_directory, jar_name) }
+      FileUtils.mkdir_p target_directory
+      download(version, uri, description) { |file| FileUtils.cp file.path, (target_directory + jar_name) }
     end
 
     # The home directory for this component

spec/java_buildpack/application/java_home_spec.rb

@@ -0,0 +1,33 @@
+# Encoding: utf-8
+# Cloud Foundry Java Buildpack
+# Copyright 2013 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 'spec_helper'
+require 'application_helper'
+
+describe JavaBuildpack::Application::JavaHome do
+  include_context 'application_helper'
+
+  let(:java_home) { application.component_directory('test-java-home') }
+
+  before do
+    application.java_home.set java_home
+  end
+
+  it 'should set JAVA_HOME environment variable' do
+    application.java_home.do_with { expect(ENV['JAVA_HOME']).to eq("$PWD/#{java_home.relative_path_from app_dir}") }
+  end
+
+end