Rhythmk 一步一步学 JAVA (22) JAVA 网络编程

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) ....