URL 的具体分析

1. 创建 URL

 

URL(String spec)
URL(String protocol, String host, String file) 

 

创建URL 相对路径时，有一个构造方法
URLs at the Gamelan site:
 http://www.gamelan.com/pages/Gamelan.game.html
 http://www.gamelan.com/pages/Gamelan.net.html

 

java URL object 对象构造

 

URL gamelan = new URL("http://www.gamelan.com/pages/");
URL gamelanGames = new URL(gamelan, "Gamelan.game.html");
URL gamelanNetwork = new URL(gamelan, "Gamelan.net.html");

 

创建 URL 注意， 如果碰到特殊字符 如空格，可以依据一下方式转换. 

如果链接为:  http://foo.com/hello world/
则对应的java URL 对象为： URL url = new URL("http://foo.com/hello%20world");

注：如果不确定那些特殊字符需要编码, 可以使用 java.net.URI 类

 

URI uri = new URI("http", "foo.com", "/hello world/", "");
URL url = uri.toURL();

 

 

2. 解析 URL

 

URL url = new URL("http://java.sun.com:80/docs/books/tutorial/index.html?name=networking#DOWNLOADING";
 System.out.println("authority: " + url.getAuthority());
 System.out.println("host: " + url.getHost());
 System.out.println("port: " + url.getPort());
 System.out.println("query: " + url.getQuery());
 System.out.println("path: " + url.getPath());
 System.out.println("file: " + url.getFile());
 System.out.println("content: " + url.getContent());
 System.out.println("ref: " + url.getRef());

 

 

 

3. 读取 URL 里面的内容

URL url = null;
url = new URL("http://www.163.com");
  
BufferedReader reader = new BufferedReader(
    new InputStreamReader(url.openStream()));
  
String currentLine = null;
while((currentLine = reader.readLine()) != null) {
   System.out.println(currentLine);
}

 

4. 连接到 URL

当然，connect()方法不是必要的，如有些操作(getInputStream()等）会自动依赖于
connect() 方法，当然如果有必要，还是要显示调用

 

 try {
  URL yahoo = new URL("http://www.yahoo.com/");
  URLConnection yahooConnection = yahoo.openConnection();
  yahooConnection.connect();

 } catch (MalformedURLException e) {     // new URL() failed
  . . .
 } catch (IOException e) {               // openConnection() failed
  . . .
 }

 

 

 

注： 一般不只直接要url 得到InputStream等，用URLConnection 获得Steam 比较好.

 

5. 写入内容到URL 中

例如: 写入一个字符串到URL, 然后服务器得到后，反向字符串后返回.
一般按以下步骤执行

   1. Create a URL.
   2. Retrieve the URLConnection object.
   3. Set output capability on the URLConnection. urlConnection.setDoOutput(true);
   4. Open a connection to the resource.
   5. Get an output stream from the connection.
   6. Write to the output stream.
    7. Close the output stream.

 

URL url = new URL(args[0]);
URLConnection con = url.openConnection();
 
con.setDoOutput(true);
OutputStreamWriter out = new OutputStreamWriter(con.getOutputStream());
out.write("String =" + encodeStr);
out.flush();
out.close();

  

 

访问方式为
java TestURLConnectionWriter http://localhost:8080/urltest/reverse abc

服务器端用Servlet处理，具体见附件代码