Rack::Builder

What is Rack::Builder ?

 

Rack::Builder是一种很小的，用来构件Rack应用程序的DSL语言

Rack::Builder将Rack middlewares和applications结合起来，转换成一个真正的rack application，可以把Rack::Builder比作是栈，底层是你的rack application，中间件在其上，而整个栈本身也是一个rack application。

 

切换到rails工程目录下，执行rack config.ru会在工程的根目录下生成一个config.ru的文件，修改文件内容如下

 

require ::File.expand_path('../config/environment',  __FILE__)
run Proc.new {|env| [200, {"Content-Type" => "text/html"}, ["Hello Rack!"]]}

 

重新启动服务器，rack config.ru，打开 http://localhost:9292 页面显示为 Hello，Rack！

 

Rack::Builder 的三个重要的实例方法

 

1. Rack::Builder#run

 

infinity = Proc.new {|env| [200, {"Content-Type" => "text/html"}, [env.inspect]]}
builder = Rack::Builder.new
builder.run infinity
Rack::Handler::WEBrick.run builder, :Port => 9292

 

Rack::Bulder#initialize同样支持代码块

 

 

infinity = Proc.new {|env| [200, {"Content-Type" => "text/html"}, [env.inspect]]}
builder = Rack::Builder.new do
  run infinity
end
Rack::Handler::WEBrick.run builder, :Port => 9292

 

2. Rack::Builder#use

Rack::Bulder#use将中间价加入到rack application中，rack 有很多有用的中间件，其中之一有Rack::CommonLogger

 

infinity = Proc.new {|env| [200, {"Content-Type" => "text/html"}, [env.inspect]]}
builder = Rack::Builder.new do
  use Rack::CommonLogger
  run infinity
end
Rack::Handler::WEBrick.run builder, :Port => 9292

 

3. Rack::Builder#map

Rack::Bulder#map 类似于rails中routes中的map，用来做路由

 

 

infinity = Proc.new {|env| [200, {"Content-Type" => "text/html"}, [env.inspect]]}
builder = Rack::Builder.new do
  use Rack::CommonLogger
  map '/' do
    run infinity
  end

  map '/version' do
    run Proc.new {|env| [200, {"Content-Type" => "text/html"}, ["infinity 0.1"]] }
  end

end
Rack::Handler::WEBrick.run builder, :Port => 9292

 

需要注意的是：当访问的url于version匹配上，则显示infinity 0.1，

比如： http://localhost:9292/version, http://localhost:9292/version/xxx

如果没有匹配上，则显示系统信息 ，比如  

http://localhost:9292/,  http://localhost:9292/versiontest,  http://localhost:9292/xxx

 

同样支持嵌套的格式，如下

 

 

require ::File.expand_path('../config/environment',  __FILE__)
infinity = Proc.new {|env| [200, {"Content-Type" => "text/html"}, [env.inspect]]}
builder = Rack::Builder.new do
  use Rack::CommonLogger

  map '/' do
    run infinity
  end

  map '/version' do
    map '/' do
      run Proc.new {|env| [200, {"Content-Type" => "text/html"}, ["infinity 0.1"]] }
    end

    map '/last' do
      run Proc.new {|env| [200, {"Content-Type" => "text/html"}, ["infinity beta 0.0"]] }
    end
  end
end
Rack::Handler::WEBrick.run builder, :Port => 9292

 

http://localhost:9292/version/last 返回：infinity beta 0.0

http://localhost:9292/version/lastxx 返回：infinity 0.1

http://localhost:9292/,http://localhost:9292/xxx  返回：系统信息

 

原文资料：http://m.onkey.org/ruby-on-rack-2-the-builder