make sure "optimized" File streaming gets used

- with Rails 3.x there seems to always be a body wrapping
  even while returning a File instance body, thus check for
  body_parts on the body object

- besides this java file channel use avoids a nasty bug with 1.6.7
  in --1.9 mode  - while binary files are iterated using File.each the
  lines end up havind the default internal encoding which in case
  of rails is Encoding.default_internal = Encoding::UTF_8 and thus
  end up being incorrectly converted to_java_bytes (@see #107)

Author: kares

src/main/ruby/jruby/rack/response.rb

@@ -11,14 +11,6 @@ class Response
       include org.jruby.rack.RackResponse
       java_import java.nio.channels.Channels
 
-      @@object_polluted = begin
-                            # Fixnum should not have this method, and it
-                            # shouldn't be on Object
-                            Fixnum.method('to_channel').owner == Object
-                          rescue
-                            false
-                          end
-
       def initialize(arr)
         @status, @headers, @body = *arr
       end
@@ -36,9 +28,9 @@ def chunked?
       end
 
       def getBody
-        b = ""
-        @body.each {|part| b << part }
-        b
+        body = ""
+        @body.each { |part| body << part }
+        body
       ensure
         @body.close if @body.respond_to?(:close)
       end
@@ -91,12 +83,19 @@ def write_body(response)
         begin
           if @body.respond_to?(:call) && ! @body.respond_to?(:each)
             @body.call(outputstream)
-          elsif @body.respond_to?(:to_channel) && !object_polluted_with_anyio?(@body, :to_channel)
+          elsif @body.respond_to?(:to_channel) && 
+              ! object_polluted_with_anyio?(@body, :to_channel)
             @body = @body.to_channel # so that we close the channel
             transfer_channel(@body, outputstream)
-          elsif @body.respond_to?(:to_inputstream) && !object_polluted_with_anyio?(@body, :to_inputstream)
+          elsif @body.respond_to?(:to_inputstream) && 
+              ! object_polluted_with_anyio?(@body, :to_inputstream)
             @body = @body.to_inputstream # so that we close the stream
             transfer_channel(Channels.newChannel(@body), outputstream)
+          elsif @body.respond_to?(:body_parts) && @body.body_parts.respond_to?(:to_channel) && 
+              ! object_polluted_with_anyio?(@body.body_parts, :to_channel)
+            # ActionDispatch::Response "raw" body access in case it's a File
+            @body = @body.body_parts.to_channel # so that we close the channel
+            transfer_channel(@body, outputstream)
           else
             # 1.8 has a String#each method but 1.9 does not :
             method = @body.respond_to?(:each_line) ? :each_line : :each
@@ -117,12 +116,16 @@ def write_body(response)
         end
       end
 
+      private
+      
+      BUFFER_SIZE = 16 * 1024
+      
       def transfer_channel(channel, outputstream)
         outputchannel = Channels.newChannel outputstream
         if channel.respond_to?(:transfer_to)
           channel.transfer_to(0, channel.size, outputchannel)
         else
-          buffer = java.nio.ByteBuffer.allocate(16384)
+          buffer = java.nio.ByteBuffer.allocate(BUFFER_SIZE)
           while channel.read(buffer) != -1
             buffer.flip
             outputchannel.write(buffer)
@@ -135,14 +138,22 @@ def transfer_channel(channel, outputstream)
         end
       end
 
+      @@object_polluted = begin
+                            # Fixnum should not have this method, and it
+                            # shouldn't be on Object
+                            Fixnum.method('to_channel').owner == Object
+                          rescue
+                            false
+                          end
+      
       # See http://bugs.jruby.org/5444 - we need to account for pre-1.6
       # JRuby where Object was polluted with #to_channel by
       # IOJavaAddions.AnyIO
       def object_polluted_with_anyio?(obj, meth)
-        begin
+        @@object_polluted && begin
           # The object should not have this method, and
           # it shouldn't be on Object
-          @@object_polluted && obj.method(meth).owner == Object
+          obj.method(meth).owner == Object
         rescue
           false
         end

src/spec/ruby/jruby/rack/response_spec.rb

@@ -199,7 +199,35 @@ class << str; undef_method :each; end if str.respond_to?(:each)
 
       @response.write_body(@servlet_response)
     end
+    
+    it "streams a file using a channel if wrapped in body_parts", 
+      :lib => [ :rails30, :rails31, :rails32 ] do
+      require 'action_dispatch/http/response'
+      
+      path = File.expand_path('../../files/image.jpg', File.dirname(__FILE__))
+      file = File.open(path, 'rb')
+      headers = { 
+        "Content-Disposition"=>"attachment; filename=\"image.jpg\"", 
+        "Content-Transfer-Encoding"=>"binary", 
+        "Content-Type"=>"image/jpeg" 
+      }
+      # we're emulating the body how rails returns it (for a file response)
+      body = ActionDispatch::Response.new(200, headers, file)
+      body = Rack::BodyProxy.new(body) { nil } if defined?(Rack::BodyProxy)
+      # Rack::BodyProxy not available with Rails 3.0.x
+      # with 3.2 there's even more wrapping with ActionDispatch::BodyProxy
+      
+      response = JRuby::Rack::Response.new [ 200, headers, body ]
+      stream = self.stream
+      response.should_receive(:transfer_channel).with do |ch, s|
+        s.should == stream 
+        ch.should be_a java.nio.channels.FileChannel
+        ch.size.should == File.size(path)
+      end
 
+      response.write_body(@servlet_response)
+    end
+    
     it "uses #transfer_to to copy the stream if available" do
       channel = mock "channel"
       @body.should_receive(:to_channel).and_return channel