# 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](https://zh.wikipedia.org/wiki/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)](https://zh.wikipedia.org/wiki/XML-RPC)

    ```
    <?xml version="1.0"?>
    <methodCall>
    <methodName>examples.getStateName</methodName>
    <params>
      <param>
          <value><i4>40</i4></value>
      </param>
    </params>
    </methodCall>
    ```
  * [使用範例 (Python)](http://python3-cookbook.readthedocs.io/zh_CN/latest/c11/p06_implement_simple_remote_procedure_call_with_xml_rpc.html)
    * 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](https://jenhsuan.gitbooks.io/asp-net/content/412introduction-of-soap.html))
  * 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](http://www.cnblogs.com/JeffreySun/archive/2009/12/14/1623766.html)

    ```
    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](https://jenhsuan.gitbooks.io/javascript-node-js/content/chapter1/1234json-yu-wu-jian-shi-ti.html))
  * <HTTP://JSON.ORG> launch in 2002
  * Google & Yahoo offered JSON/RPC, REST in 2006


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