Java 从 URL 字符串中提取主机名/域名
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Extract host name/domain name from URL string
提问by Anand
I have a URL like http://hostname:port_no/control/login.jsp.
我有一个像http://hostname:port_no/control/login.jsp.
I have the above url stored in some String.Now, I need to extract hostnamefrom the String.
我将上面的 url 存储在一些hostname字符串中。现在，我需要从字符串中提取。
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。
采纳答案by KarelG
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，并且如果您的主机名确实以hostname.com/...或开头www.hostname.com/...，则它是万无一失的，它将以“主机名”返回。
If the given urlis invalid (undefined hostname), it returns with null.
如果给定url无效（未定义的主机名），则返回 null。
回答by PeterMmm
java.net.URL u = new URL("http://hostname:port_no/control/login.jsp");
System.err.println(u.getHost());
回答by niiraj874u
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();
}
回答by astack
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];
回答by luiscosta
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。
回答by Gregory Alan Bolcer
@KarelG's answer is the best answer, though I had specific issues with certain non-standard domains. The example issue is self contained below.
@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。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. This is the changed code.
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。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);
}
}
回答by Freddie
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。
