Rhythmk 一步一步学 JAVA (22) JAVA 网络编程

时间：2022-03-21 06:20

1、获取主机信息

@Test public void GetDomainInfo() throws UnknownHostException { String domain = "www.baidu.com"; InetAddress netAddress = InetAddress.getByName(domain); // 获取主机名 System.out.println(netAddress.getHostName()); // IP地址 System.out.println(netAddress.getCanonicalHostName()); InetAddress ip2domain = InetAddress.getByAddress(new byte[] { (byte) 115, (byte) 239, (byte) 210, (byte) 26 }); System.out.println(ip2domain.getCanonicalHostName()); System.out.println(ip2domain.getHostName()); /* * 输出： www.baidu.com 115.239.210.26 115.239.210.26 115.239.210.26 */ }

　　2、URLEncode 跟 URLDecoder

// URLDecoder和URLEncoder @SuppressWarnings("deprecation") @Test public void URLEncode() { String result = URLEncoder.encode("我是Rhythmk,你呢？"); System.out.println(result); // 输出： // %E6%88%91%E6%98%AFRhythmk%2C%E4%BD%A0%E5%91%A2%EF%BC%9F } @Test public void URLDecoder() { String result = java.net.URLDecoder .decode("%E6%88%91%E6%98%AFRhythmk%2C%E4%BD%A0%E5%91%A2%EF%BC%9F"); System.out.println(result); /* * 输出：我是Rhythmk,你呢？ */ }

3、POST GET 请求

@Test public void Get() throws IOException { URLConnection urlConnect; URL url = new URL("http://www.baidu.com"); urlConnect = url.openConnection(); BufferedReader biStream = null; try { urlConnect.connect(); Map<String, List<String>> map = urlConnect.getHeaderFields(); for (String key : map.keySet()) { List<String> listKey = map.get(key); for (String k : listKey) { System.out.println("*****************" + k); } } biStream = new BufferedReader(new InputStreamReader( urlConnect.getInputStream())); String html = ""; String line = null; while ((line = biStream.readLine()) != null) { html += line; } System.out .println("************************* HTML 内容 ***********************"); System.out.println(html); } catch (Exception e) { e.printStackTrace(); } finally { if (biStream != null) { biStream.close(); } } } @Test public void Post() throws IOException { BufferedReader biStream = null; try { URL url = new URL("http://passport.rhythmk.com/signin"); URLConnection urlConnect = url.openConnection(); // 设置通用的请求属性 urlConnect.setRequestProperty("accept", "*/*"); urlConnect.setRequestProperty("connection", "Keep-Alive"); urlConnect.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)"); // 发送POST请求必须设置如下两行 ,需要在connect 之前设定好 urlConnect.setDoOutput(true); urlConnect.setDoInput(true); urlConnect.connect(); // 获取URLConnection对象对应的输出流 PrintWriter out = new PrintWriter(urlConnect.getOutputStream()); // 发送请求参数 out.print("returnUrl=http%3A%2F%2Fwww.ciwong.com%2F&username=a&password=d"); // flush输出流的缓冲 out.flush(); biStream = new BufferedReader(new InputStreamReader( urlConnect.getInputStream())); String html = ""; String line = null; while ((line = biStream.readLine()) != null) { html += line; } System.out .println("************************POST* HTML 内容 ***********************"); System.out.println(html); } catch (Exception e) { e.printStackTrace(); } finally { if (biStream != null) { biStream.close(); } } }

　　注意：

如果先

urlConnect.connect();

然后如下设置

urlConnect.setDoOutput(true);
urlConnect.setDoInput(true);

导致异常：

java.lang.IllegalStateException: Already connected

at java.net.URLConnection.setDoOutput(URLConnection.java:849)
at com.rhythmk.filedemo.net_demo1.Post(net_demo1.java:126) ....

Rhythmk 一步一步学 JAVA (22) JAVA 网络编程,gxlsystem