java.net--URL

URI：统计资源标示。
URL ：统计资源定位符
笼统地说，每个 URL 都是 URI，但不一定每个 URI 都是 URL。这是因为 URI 还包括一个子类，即统一资源名称 (URN)，它命名资源但不指定如何定位资源。

1. Converting Between a URL and a URI    URI与URL之间的转化

       URI uri = null;
       URL url = null;
       uri = new URI("file://F:/test.xml");
        // Convert a URI to a URL
       url = uri.toURL();
        // Convert a URL to a URI
       uri =url.toURI();

   2. Parsing a URL   解析一个url

      url = new URL("http://localhost:8080/pplive.htm#ppstream");
      String protocol = url.getProtocol(); //http
      String host = url.getHost();         //localhost
      int port = url.getPort();            //8080
      String file = url.getFile();         // /pplive
      String ref = url.getRef();           //ppstream

  3. Sending a POST Request Using a URL

      Client:

      String data = URLEncoder.encode("key1","UTF-8")+"="+URLEncoder.encode("value1","UTF-8");
            data += "&"+URLEncoder.encode("key2","UTF-8")+"="+URLEncoder.encode("value2","UTF-8");
            System.out.println(data);
            
            URL url = new URL("http://127.0.0.1:56231/test/test/");                //切忌不要把应用名称给忘记了
            URLConnection con = url.openConnection();
            
            //send data
            con.setDoOutput(true);
            con.setDoInput(true);
            
            OutputStreamWriter writer = new OutputStreamWriter(con.getOutputStream());
            writer.write(data);
            writer.flush();
            
            //get response
            BufferedReader br = new BufferedReader(new InputStreamReader(con.getInputStream()));
            String line = null;
            while((line = br.readLine()) != null){
                System.out.println(line);
            }
            writer.close();
            br.close();

    Service:

        request.setCharacterEncoding("UTF-8");
        response.setCharacterEncoding("UTF-8");
        
        BufferedReader br = new BufferedReader(new InputStreamReader(request.getInputStream()));        //这个例子还是有点问题的
        String line = null;
        StringBuilder sb = new StringBuilder();
        while((line = br.readLine()) != null){
            sb.append(line);
        }
        System.out.println(sb.toString());
        PrintWriter pw = new PrintWriter(response.getOutputStream(),true);
        String data = "i'am back !";
        pw.write(data);
        pw.flush();
        pw.close();
        br.close();