```ruby
# Copyright 2014 TIS inc.
#
# 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.
class SystemsController < Sinatra::Base
  configure :development do
    register Sinatra::Reloader
  end

  get '/' do
    json System.all
  end

  get '/:id' do
    json System.find(params[:id])
  end

  post '/' do
    system = System.new permit_params
    system.save

    json system
  end

  def permit_params
    ActionController::Parameters.new(params)
      .permit(:name, :template_body, :template_url, :parameters, :primary_cloud_id, :secondary_cloud_id)
  end
end
```

Switch status code and response body by validation result
user
```ruby
# Copyright 2014 TIS inc.
#
# 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.
class SystemsController < Sinatra::Base
  configure :development do
    register Sinatra::Reloader
  end

  get '/' do
    json System.all
  end

  get '/:id' do
    json System.find(params[:id])
  end

  post '/' do
    system = System.new permit_params
    unless system.save
      status 400
      return json system.errors
    end

    status 201
    json system
  end

  def permit_params
    ActionController::Parameters.new(params)
      .permit(:name, :template_body, :template_url, :parameters, :primary_cloud_id, :secondary_cloud_id)
  end
end
```
assistant