3.1.1.Evolution of REST/JSON API

• Web service

  • This is used for easy communication over a network between two electronic devices

  • RPC, XML-RPC -> 2003 SOAP (XML-base) -> Google & Yahoo offered JSON/RPC, REST in 2006

• RPC

  • 遠程調用框架

  • 從一台機器 (客戶端)上通過參數傳遞調用另一台機器 (服務器)上的一個函數或方法

  • 使用形式上像調用本地函數 (或方法)一樣調用遠程函數 (或方法)

  • RPC風格的web service跨語言性不佳

• XML-RPC, JSON-RPC

  • XML-RPC透過向裝置了這個協定的伺服器發出HTTP請求。發出請求的用戶端一般都是需要向遠端系統要求呼叫的軟體

  • 數據格式範例 (請求)

    <?xml version="1.0"?>
    <methodCall>
    <methodName>examples.getStateName</methodName>
    <params>
      <param>
          <value><i4>40</i4></value>
      </param>
    </params>
    </methodCall>

  • 使用範例 (Python)

    • 服務器端

      from xmlrpc.server import SimpleXMLRPCServer
      
      class KeyValueServer:
        _rpc_methods_ = ['get', 'set', 'delete', 'exists', 'keys']
        def __init__(self, address):
            self._data = {}
            self._serv = SimpleXMLRPCServer(address, allow_none=True)
            for name in self._rpc_methods_:
            self._serv.register_function(getattr(self, name))
      
      def get(self, name):
        return self._data[name]
      
      def set(self, name, value):
        self._data[name] = value
      
      def delete(self, name):
        del self._data[name]
      
      def exists(self, name):
        return name in self._data
      
      def keys(self):
        return list(self._data)
      
      def serve_forever(self):
        self._serv.serve_forever()
      
      # Example
      if __name__ == '__main__':
        kvserv = KeyValueServer(('', 15000))
        kvserv.serve_forever()

    • 客戶端

      >>> from xmlrpc.client import ServerProxy
      >>> s = ServerProxy('http://localhost:15000', allow_none=True)
      >>> s.set('foo', 'bar')
      >>> s.set('spam', [1, 2, 3])
      >>> s.keys()
      ['spam', 'foo']
      >>> s.get('foo')
      'bar'
      >>> s.get('spam')
      [1, 2, 3]
      >>> s.delete('spam')
      >>> s.exists('spam')
      False
      >>>

• SOAP (Simple Object Access Protocol)

  • 數據交換協議規範

  • XML based standard, Document風格的web service有以下問題:

    • Issues of XML based Protocol

    • XML is heavy in terms of network traffic, large payload

    • Parsing of XML is CPU & memory intensive

    • Slow performance of XML on browser front end not desired

    • Mobile devices battery performance reduced due to XML

    • Standards & versions of standards caused confusion and complexity

    • Mobile and Single page application developers were not happy

  • 跨平台, 跨語言

  • Defined:

    • structure of the messages exchanged, security, transaction, other standards

  • SOAP請求範例

    POST /WebServices/WeatherWebService.asmx HTTP/1.1
    
    User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; MS Web Services Client Protocol 2.0.50727.3603)
    Content-Type: text/xml; charset=utf-8
    SOAPAction: "http://WebXml.com.cn/getSupportCity"
    Host: www.webxml.com.cn
    Content-Length: 348
    Expect: 100-continue
    Connection: Keep-Alive
    
    <?xml version="1.0" encoding="utf-8"?><soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
      <soap:Body>
          <getSupportCity xmlns="http://WebXml.com.cn/">
              <byProvinceName>广东</byProvinceName>
          </getSupportCity>
      </soap:Body>        
    </soap:Envelope>

  • 使用範例

    • WSDL: http://www.cnblogs.com/JeffreySun/archive/2009/12/14/1623766.html

• JSON (JavaScript Object Notation)

  • HTTP://JSON.ORG launch in 2002

  • Google & Yahoo offered JSON/RPC, REST in 2006