URL 的具体分析
1. 创建 URLURL(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);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
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