Conditional Tomcat Configuration

In an earlier, naive, attempt to make Tomcat 8 the default, the code did not take into account that certain
configuration options have changed.  This commit fixes the code so that resource linking is done properly depending on
whether Tomcat 8 or pre-Tomcat 8 is used and only adds the JasperListener to pre-Tomcat 8 is used.

[#78317410][resolves #95]

Author: nebhale

lib/java_buildpack/container/tomcat/tomcat_instance.rb

@@ -18,6 +18,7 @@
 require 'java_buildpack/component/versioned_dependency_component'
 require 'java_buildpack/container'
 require 'java_buildpack/container/tomcat/tomcat_utils'
+require 'java_buildpack/util/tokenized_version'
 
 module JavaBuildpack
   module Container
@@ -54,12 +55,45 @@ def supports?
 
       private
 
+      TOMCAT_8 = JavaBuildpack::Util::TokenizedVersion.new('8.0.0').freeze
+
+      private_constant :TOMCAT_8
+
+      def configure_jasper
+        return unless @version < TOMCAT_8
+
+        document = read_xml server_xml
+        server   = REXML::XPath.match(document, '/Server').first
+
+        listener = REXML::Element.new('Listener')
+        listener.add_attribute 'className', 'org.apache.catalina.core.JasperListener'
+
+        server.insert_before '//Service', listener
+
+        write_xml server_xml, document
+      end
+
+      def configure_linking
+        document = read_xml context_xml
+        context  = REXML::XPath.match(document, '/Context').first
+
+        if @version < TOMCAT_8
+          context.add_attribute 'allowLinking', true
+        else
+          context.add_element 'Resources', 'allowLinking' => true
+        end
+
+        write_xml context_xml, document
+      end
+
       def expand(file)
         with_timing "Expanding Tomcat to #{@droplet.sandbox.relative_path_from(@droplet.root)}" do
           FileUtils.mkdir_p @droplet.sandbox
           shell "tar xzf #{file.path} -C #{@droplet.sandbox} --strip 1 --exclude webapps 2>&1"
 
           @droplet.copy_resources
+          configure_linking
+          configure_jasper
         end
       end
 

lib/java_buildpack/container/tomcat/tomcat_redis_store.rb

@@ -18,8 +18,6 @@
 require 'java_buildpack/container'
 require 'java_buildpack/container/tomcat/tomcat_utils'
 require 'java_buildpack/logging/logger_factory'
-require 'rexml/document'
-require 'rexml/formatters/pretty'
 
 module JavaBuildpack
   module Container
@@ -90,10 +88,6 @@ def add_valve(context)
         context.add_element 'Valve', 'className' => FLUSH_VALVE_CLASS_NAME
       end
 
-      def context_xml
-        @droplet.sandbox + 'conf/context.xml'
-      end
-
       def formatter
         formatter         = REXML::Formatters::Pretty.new(4)
         formatter.compact = true
@@ -107,16 +101,13 @@ def jar_name
       def mutate_context
         puts '       Adding Redis-based Session Replication'
 
-        document = context_xml.open { |file| REXML::Document.new file }
+        document = read_xml context_xml
         context  = REXML::XPath.match(document, '/Context').first
 
         add_valve context
         add_manager context
 
-        context_xml.open('w') do |file|
-          formatter.write document, file
-          file << "\n"
-        end
+        write_xml context_xml, document
       end
 
     end

lib/java_buildpack/container/tomcat/tomcat_utils.rb

@@ -15,10 +15,19 @@
 # limitations under the License.
 
 require 'java_buildpack'
+require 'rexml/document'
+require 'rexml/formatters/pretty'
 
 module JavaBuildpack
   module Container
 
+    # The Tomcat +context.xml+ file
+    #
+    # @return [Pathname] the Tomcat +context.xml+ file
+    def context_xml
+      @droplet.sandbox + 'conf/context.xml'
+    end
+
     # Link a collection of files to a destination directory, using relative paths
     #
     # @param [Array<Pathname>] source the collection of files to link
@@ -29,6 +38,21 @@ def link_to(source, destination)
       source.each { |path| (destination + path.basename).make_symlink(path.relative_path_from(destination)) }
     end
 
+    # Read an XML file into a +REXML::Document+
+    #
+    # @param [Pathname] file the file to read
+    # @return [REXML::Document] the file parsed into a +REXML::Document+
+    def read_xml(file)
+      file.open { |f| REXML::Document.new f }
+    end
+
+    # The Tomcat +server.xml+ file
+    #
+    # @return [Pathname] The Tomcat +server.xml+ file
+    def server_xml
+      @droplet.sandbox + 'conf/server.xml'
+    end
+
     # The Tomcat +lib+ directory
     #
     # @return [Pathname] the Tomcat +lib+ directory
@@ -43,5 +67,24 @@ def tomcat_webapps
       @droplet.sandbox + 'webapps'
     end
 
+    # Write a properly formatted XML file
+    #
+    # @param [Pathname] file the file to write
+    # @return [Void]
+    def write_xml(file, document)
+      file.open('w') do |f|
+        formatter.write document, f
+        f << "\n"
+      end
+    end
+
+    private
+
+    def formatter
+      formatter         = REXML::Formatters::Pretty.new(4)
+      formatter.compact = true
+      formatter
+    end
+
   end
 end

resources/tomcat/conf/context.xml

@@ -15,5 +15,5 @@
   ~ limitations under the License.
   -->
 
-<Context allowLinking='true'>
+<Context>
 </Context>

resources/tomcat/conf/server.xml

@@ -18,8 +18,6 @@
 
 <Server port='-1'>
 
-    <Listener className='org.apache.catalina.core.JasperListener'/>
-
     <Service name='Catalina'>
         <Connector port='${http.port}' bindOnInit="false"/>
 

spec/java_buildpack/container/tomcat/tomcat_instance_spec.rb

@@ -48,6 +48,28 @@
     expect(sandbox + 'conf/server.xml').to exist
   end
 
+  it 'should configure for Tomcat 7',
+     app_fixture:   'container_tomcat',
+     cache_fixture: 'stub-tomcat.tar.gz' do
+
+    component.compile
+    expect((sandbox + 'conf/context.xml').read).to match(/<Context allowLinking='true'>/)
+    expect((sandbox + 'conf/server.xml').read).to match(/<Listener className='org.apache.catalina.core.JasperListener'\/>/)
+  end
+
+  context do
+    let(:version) { '8.0.12' }
+
+    it 'should configure for Tomcat 8',
+       app_fixture:   'container_tomcat',
+       cache_fixture: 'stub-tomcat.tar.gz' do
+
+      component.compile
+      expect((sandbox + 'conf/context.xml').read).to match(/<Context>[\s]*<Resources allowLinking='true'\/>/)
+      expect((sandbox + 'conf/server.xml').read).not_to match(/<Listener className='org.apache.catalina.core.JasperListener'\/>/)
+    end
+  end
+
   it 'should link only the application files and directories to the ROOT webapp',
      app_fixture:   'container_tomcat_with_index',
      cache_fixture: 'stub-tomcat.tar.gz' do