[英]Extract host name/domain name from URL string
I have a URL like http://hostname:port_no/control/login.jsp
.我有一个像
http://hostname:port_no/control/login.jsp
这样的 URL。
I have the above url stored in some String.Now, I need to extract hostname
from the String.我将上面的 url 存储在一些字符串中。现在,我需要从字符串中提取
hostname
。
I am doing like this in my Java code我在我的 Java 代码中这样做
String domain = url.substring(url.indexOf('/') + 2, url.lastIndexOf(':'));
I want to know if there is any better way to do the same.我想知道是否有更好的方法来做同样的事情。
You can use the java.net.URI
-class to extract the hostname from the string.您可以使用
java.net.URI
-class 从字符串中提取主机名。
Here below is a method from which you can extract your hostname from a string.下面是一种可以从字符串中提取主机名的方法。
public String getHostName(String url) {
URI uri = new URI(url);
String hostname = uri.getHost();
// to provide faultproof result, check if not null then return only hostname, without www.
if (hostname != null) {
return hostname.startsWith("www.") ? hostname.substring(4) : hostname;
}
return hostname;
}
This above gives you the hostname, and is faultproof if your hostname does start with either hostname.com/...
or www.hostname.com/...
, which will return with 'hostname'.以上为您提供了主机名,如果您的主机名确实以
hostname.com/...
或www.hostname.com/...
开头,则会以“主机名”返回。
If the given url
is invalid (undefined hostname), it returns with null.如果给定的
url
无效(未定义的主机名),则返回 null。
java.net.URL aURL;
try {
aURL = new java.net.URL("http://example.com:80/docs/");
System.out.println("host = " + aURL.getHost()); //example.com
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
java.net.URL u = new URL("http://hostname:port_no/control/login.jsp");
System.err.println(u.getHost());
If you want string work, then try the following code sample,如果您想要字符串工作,请尝试以下代码示例,
String URL= "http://hostname:port_no/control/login.jsp";
String s_URL[] = ULR.split("//");
String s1 = s_URL[1];
String s2[] = s1.split(":");
String hostname = s2[0];
In Java:在 Java 中:
String hostname = url.split("://")[1].split(":")[0];
String portnumber = url.split("://")[1].split(":")[1].split("/")[0];
Hope this helps.希望这可以帮助。
@KarelG's answer is the best answer, though I had specific issues with certain non-standard domains. @KarelG 的答案是最好的答案,尽管我对某些非标准域有具体问题。 The example issue is self contained below.
示例问题在下面是自包含的。
For certain "real world" input values, I had to add a check to the URI scheme to avoid mis-parsing of some addresses.对于某些“真实世界”的输入值,我必须向 URI 方案添加一个检查,以避免错误解析某些地址。 This is the changed code.
这是更改后的代码。
import java.net.URI;
import java.net.*;
public class Domain {
public static String getDomainName(String url) {
try {
URI uri = new URI(url);
String domain = uri.getHost();
System.out.println("domain: " + domain);
if (uri.getScheme() != null) {
return domain.startsWith("www.") ? domain.substring(4) : domain;
} else {
return uri.getSchemeSpecificPart();
}
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
}
Below is the test case and value that was failing.下面是失败的测试用例和值。
Domain.java javac Domain.java java Domain域.java javac 域.java java 域
import java.net.URI;
import java.net.*;
import java.io.*;
public class Domain {
public static String longname = "https://www.3dprintingmedia.network/longform/page.html";
public static String name = "www.3dprintingmedia.network";
public static void getDomain(String url) {
try {
URI uri = new URI(url);
String domain = uri.getHost();
System.out.println("protocol: " + uri.getScheme());
System.out.println("path: " + uri.getPath());
System.out.println("name: " + name);
System.out.println("domain: " + domain);
System.out.println(domain.startsWith("www.") ? domain.substring(4) : domain);
} catch (Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
System.out.println("Parsing domain: " + name);
getDomain(longname);
getDomain(name);
System.exit(0);
}
}
A solution using Regular expression and group:使用正则表达式和组的解决方案:
String pattern = "(\\w*://)([\\w-_.]+)([:\\w\\W]*)";
Pattern r = Pattern.compile(pattern);
Matcher m = r.matcher(a);
if (m.find())
{
System.out.println(m.group(0));
System.out.println(m.group(1));
System.out.println(m.group(2));
System.out.println(m.group(3));
}
group(2) is the hostname. group(2) 是主机名。
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