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) ....

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