diff --git a/Gemfile b/Gemfile
index 96f5cc1..ae1e230 100644
--- a/Gemfile
+++ b/Gemfile
@@ -10,8 +10,8 @@ group :development, :test do
   gem "bundler", "~> 1.0"
   gem "rspec", "~> 2.6"
   gem "jeweler", "~> 1.6"
-  gem "thin", "~> 1.5"
-  gem "unicorn", "~> 4.5"
+  gem "thin", "~> 1.5", :platform => :ruby
+  gem "unicorn", "~> 4.5", :platform => :ruby
   gem "puma", "~> 1.6"
   gem "em-http-request", "~> 1.0"
 end
diff --git a/spec/lib/heroku/forward/backends/thin_spec.rb b/spec/lib/heroku/forward/backends/thin_spec.rb
index a7b92d0..10b9d6d 100644
--- a/spec/lib/heroku/forward/backends/thin_spec.rb
+++ b/spec/lib/heroku/forward/backends/thin_spec.rb
@@ -1,94 +1,93 @@
-require 'spec_helper'
-require 'heroku/forward/backends/thin'
+unless RUBY_PLATFORM == "java"
+  require 'spec_helper'
+  require 'heroku/forward/backends/thin'
 
-describe Heroku::Forward::Backends::Thin do
-
-  describe "without ssl" do
-    let(:backend) do
-      Heroku::Forward::Backends::Thin.new
-    end
-    
-    after do
-      backend.terminate!
-    end
-
-    it "#spawned?" do
-      backend.spawned?.should be_false
-    end
-    
-    it "doesn't generate socket file" do
-      File.exists?(backend.socket).should_not be_true
-    end
+  describe Heroku::Forward::Backends::Thin do
+    describe "without ssl" do
+      let(:backend) do
+        Heroku::Forward::Backends::Thin.new
+      end
 
-    context "checks" do
-      it "checks for application" do
-        expect {
-          backend.spawn!
-        }.to raise_error Heroku::Forward::Errors::MissingBackendOptionError
+      after do
+        backend.terminate!
       end
 
-      it "checks that the application file exists" do
-        expect {
-          backend.application = 'spec/foobar'
-          backend.spawn!
-        }.to raise_error Heroku::Forward::Errors::MissingBackendApplicationError
+      it "#spawned?" do
+        backend.spawned?.should be_false
       end
 
-    end
-    
-    describe "#spawn!" do
-      before do
-        backend.application = "spec/support/app.ru"
+      it "doesn't generate socket file" do
+        File.exists?(backend.socket).should_not be_true
       end
-      
-      it "starts successfully" do
-        backend.spawn!.should_not == 0
-        sleep 2
-        backend.terminate!.should be_true
+
+      context "checks" do
+        it "checks for application" do
+          expect {
+            backend.spawn!
+          }.to raise_error Heroku::Forward::Errors::MissingBackendOptionError
+        end
+
+        it "checks that the application file exists" do
+          expect {
+            backend.application = 'spec/foobar'
+            backend.spawn!
+          }.to raise_error Heroku::Forward::Errors::MissingBackendApplicationError
+        end
+
       end
-      
-      it "generates socket file that outlives garbage-collection" do
-        backend.spawn!
-        sleep 2
-        lambda { GC.start }.should_not raise_error
-        File.exists?(backend.socket).should be_true
+
+      describe "#spawn!" do
+        before do
+          backend.application = "spec/support/app.ru"
+        end
+
+        it "starts successfully" do
+          backend.spawn!.should_not == 0
+          sleep 2
+          backend.terminate!.should be_true
+        end
+
+        it "generates socket file that outlives garbage-collection" do
+          backend.spawn!
+          sleep 2
+          lambda { GC.start }.should_not raise_error
+          File.exists?(backend.socket).should be_true
+        end
       end
+
     end
-    
-  end
 
-  describe "with SSL" do
-    let(:application) { "spec/support/app.ru" }
-    let(:mock_ssl_cert_file) { "foo" }
-    let(:mock_ssl_key_file) { "bar" }
-    let(:socket) { "foobar" }
+    describe "with SSL" do
+      let(:application) { "spec/support/app.ru" }
+      let(:mock_ssl_cert_file) { "foo" }
+      let(:mock_ssl_key_file) { "bar" }
+      let(:socket) { "foobar" }
 
-    let(:backend) do
-      Heroku::Forward::Backends::Thin.new({
-        :application => application,
-        :socket => socket,
-        :ssl => true,
-        :ssl_verify => true,
-        :ssl_key_file => mock_ssl_key_file,
-        :ssl_cert_file => mock_ssl_cert_file
-      })
-    end
+      let(:backend) do
+        Heroku::Forward::Backends::Thin.new({
+          :application => application,
+          :socket => socket,
+          :ssl => true,
+          :ssl_verify => true,
+          :ssl_key_file => mock_ssl_key_file,
+          :ssl_cert_file => mock_ssl_cert_file
+        })
+      end
 
-    it "forward SSL arguments on spawning" do
-      cmd = []
-      cmd.push "thin"
-      cmd.push "start"
-      cmd.push "-R", application
-      cmd.push "--socket", socket
-      cmd.push "-e", "development"
-      cmd.push "--ssl"
-      cmd.push "--ssl-key-file", mock_ssl_key_file
-      cmd.push "--ssl-cert-file", mock_ssl_cert_file
-      cmd.push "--ssl-verify"
-      Spoon.should_receive(:spawnp).with(* cmd).and_return(0)
-      backend.spawn!
+      it "forward SSL arguments on spawning" do
+        cmd = []
+        cmd.push "thin"
+        cmd.push "start"
+        cmd.push "-R", application
+        cmd.push "--socket", socket
+        cmd.push "-e", "development"
+        cmd.push "--ssl"
+        cmd.push "--ssl-key-file", mock_ssl_key_file
+        cmd.push "--ssl-cert-file", mock_ssl_cert_file
+        cmd.push "--ssl-verify"
+        Spoon.should_receive(:spawnp).with(* cmd).and_return(0)
+        backend.spawn!
+      end
     end
-
   end
-end
-
+end
\ No newline at end of file
diff --git a/spec/lib/heroku/forward/backends/unicorn_spec.rb b/spec/lib/heroku/forward/backends/unicorn_spec.rb
index a57831b..9c99390 100644
--- a/spec/lib/heroku/forward/backends/unicorn_spec.rb
+++ b/spec/lib/heroku/forward/backends/unicorn_spec.rb
@@ -1,61 +1,61 @@
-require 'spec_helper'
-require 'heroku/forward/backends/unicorn'
+unless RUBY_PLATFORM == "java"
+  require 'spec_helper'
+  require 'heroku/forward/backends/unicorn'
 
-describe Heroku::Forward::Backends::Unicorn do
+  describe Heroku::Forward::Backends::Unicorn do
 
-  describe "with defaults" do
-    let(:backend) do
-      Heroku::Forward::Backends::Unicorn.new
-    end
-  
-    after do
-      backend.terminate!
-    end
+    describe "with defaults" do
+      let(:backend) do
+        Heroku::Forward::Backends::Unicorn.new
+      end
 
-    it "#spawned?" do
-      backend.spawned?.should be_false
-    end
+      after do
+        backend.terminate!
+      end
 
-    context "checks" do
-      it "checks for application" do
-        expect {
-          backend.spawn!
-        }.to raise_error Heroku::Forward::Errors::MissingBackendOptionError
+      it "#spawned?" do
+        backend.spawned?.should be_false
       end
 
-      it "checks that the application file exists" do
-        expect {
-          backend.application = 'spec/foobar'
-          backend.spawn!
-        }.to raise_error Heroku::Forward::Errors::MissingBackendApplicationError
+      context "checks" do
+        it "checks for application" do
+          expect {
+            backend.spawn!
+          }.to raise_error Heroku::Forward::Errors::MissingBackendOptionError
+        end
+
+        it "checks that the application file exists" do
+          expect {
+            backend.application = 'spec/foobar'
+            backend.spawn!
+          }.to raise_error Heroku::Forward::Errors::MissingBackendApplicationError
+        end
+
       end
 
+      it "#spawn!" do
+        backend.application = "spec/support/app.ru"
+        backend.spawn!.should_not == 0
+        sleep 2
+        backend.terminate!.should be_true
+      end
     end
 
-    it "#spawn!" do
-      backend.application = "spec/support/app.ru"
-      backend.spawn!.should_not == 0
-      sleep 2
-      backend.terminate!.should be_true
-    end
-  end
-  
-  context "constructs command" do
-    
-    let(:backend) do
-      Heroku::Forward::Backends::Unicorn.new(
-        :application => 'spec/support/app.ru',
-        :env => 'test',
-        :socket => '/tmp/unicorn.sock',
-        :config_file => 'spec/support/unicorn.rb'
-      )
-    end
+    context "constructs command" do
 
-    it "forwards arguments to spawner" do
-      Spoon.should_receive(:spawnp).with(*%w{unicorn --env test --config-file spec/support/unicorn.rb --listen /tmp/unicorn.sock spec/support/app.ru}).and_return(0)
-      backend.spawn!
-    end
+      let(:backend) do
+        Heroku::Forward::Backends::Unicorn.new(
+          :application => 'spec/support/app.ru',
+          :env => 'test',
+          :socket => '/tmp/unicorn.sock',
+          :config_file => 'spec/support/unicorn.rb'
+        )
+      end
 
+      it "forwards arguments to spawner" do
+        Spoon.should_receive(:spawnp).with(*%w{unicorn --env test --config-file spec/support/unicorn.rb --listen /tmp/unicorn.sock spec/support/app.ru}).and_return(0)
+        backend.spawn!
+      end
+    end
   end
-end
-
+end
\ No newline at end of file
diff --git a/spec/lib/heroku/forward/proxy/server_spec.rb b/spec/lib/heroku/forward/proxy/server_spec.rb
index 19528c5..872a611 100644
--- a/spec/lib/heroku/forward/proxy/server_spec.rb
+++ b/spec/lib/heroku/forward/proxy/server_spec.rb
@@ -5,14 +5,15 @@
 
 describe Heroku::Forward::Proxy::Server do
 
-  [
-    Heroku::Forward::Backends::Thin,
-    Heroku::Forward::Backends::Unicorn,
-    Heroku::Forward::Backends::Puma
-  ].each do |backend_type|
+  backends = [Heroku::Forward::Backends::Puma]
 
-    context "with #{backend_type.name} backend" do
+  unless RUBY_PLATFORM == "java"
+    backends << Heroku::Forward::Backends::Thin
+    backends << Heroku::Forward::Backends::Unicorn
+  end
 
+  backends.each do |backend_type|
+    context "with #{backend_type.name} backend" do
       let(:backend) do
         backend_type.new(:application => 'spec/support/app.ru')
       end
@@ -22,7 +23,6 @@
       end
 
       context "spawned backend" do
-
         before :each do
           server.logger = Logger.new(STDOUT)
         end
@@ -44,9 +44,6 @@
           end
         end
       end
-
     end
   end
-
-end
-
+end
\ No newline at end of file