从网址获取域/主​​机名的最快方式是什么？

Question

我需要浏览一大串字符串url并从中提取域名。

例如：

http://www.stackoverflow.com/questions将提取www.stackoverflow.com

我本来使用new URL(theUrlString).getHost()但URL对象初始化增添了不少时间的过程，似乎不需要。

有没有更快速的方法来提取主机名称将是可靠的？

感谢

编辑：我的错，是万维网。将包含在上面的域名示例中。此外，这些URL可以是HTTP或HTTPS

Answer 1

如果你想处理https等，我建议你做这样的事情：

int slashslash = url.indexOf("//") + 2; 
domain = url.substring(slashslash, url.indexOf('/', slashslash)); 

注意，这是包括www部分（就像URL.getHost()会做）这实际上是域名的一部分。

编辑通过意见要求

这里有两种方法可能会有所帮助：

/** 
* Will take a url such as http://www.stackoverflow.com and return www.stackoverflow.com 
* 
* @param url 
* @return 
*/ 
public static String getHost(String url){ 
    if(url == null || url.length() == 0) 
     return ""; 

    int doubleslash = url.indexOf("//"); 
    if(doubleslash == -1) 
     doubleslash = 0; 
    else 
     doubleslash += 2; 

    int end = url.indexOf('/', doubleslash); 
    end = end >= 0 ? end : url.length(); 

    int port = url.indexOf(':', doubleslash); 
    end = (port > 0 && port < end) ? port : end; 

    return url.substring(doubleslash, end); 
} 


/** Based on : http://grepcode.com/file/repository.grepcode.com/java/ext/com.google.android/android/2.3.3_r1/android/webkit/CookieManager.java#CookieManager.getBaseDomain%28java.lang.String%29 
* Get the base domain for a given host or url. E.g. mail.google.com will return google.com 
* @param host 
* @return 
*/ 
public static String getBaseDomain(String url) { 
    String host = getHost(url); 

    int startIndex = 0; 
    int nextIndex = host.indexOf('.'); 
    int lastIndex = host.lastIndexOf('.'); 
    while (nextIndex < lastIndex) { 
     startIndex = nextIndex + 1; 
     nextIndex = host.indexOf('.', startIndex); 
    } 
    if (startIndex > 0) { 
     return host.substring(startIndex); 
    } else { 
     return host; 
    } 
} 

Answer 2

你可以写一个正则表达式？ http：//总是相同的，然后匹配所有内容，直到获得第一个'/'。

Answer 3

假设他们都是很好形成的网址，但你不”知道他们是否会为http：//，https：//开头，等

 

int start = theUrlString.indexOf('/'); 
int start = theUrlString.indexOf('/', start+1); 
int end = theUrlString.indexOf('/', start+1); 
String domain = theUrlString.subString(start, end); 
 

Answer 4

你可以尝试使用正规表达式。

http://download.oracle.com/javase/6/docs/api/java/util/regex/Pattern.html

这是一个关于Java中使用正则表达式提取域名问题：

Regular expression to retrieve domain.tld

Answer 5

你要相当小心，实现“快”​​的方式unpicking网址。网址中存在很多可能导致“快速”方法失败的可能性。例如：

• 方案（协议）部分可以写成大写和小写字母的任意组合;例如“http”，“Http”和“HTTP”是等价的。

• 权威部分可以选择性地包含用户名和/或端口号，如“http://you@example.com:8080/index.html”中所述。

• 由于DNS不区分大小写，URL的主机名部分也是（有效）不区分大小写。

• 这是合法的（虽然非常不规范）％ - 编码URL的方案或权威组件中未预留的字符。在匹配（或剥离）方案或解释主机名时，您需要考虑这一点。具有％编码字符的主机名定义为等同于解码％编码序列的主机名。

现在，如果您完全控制生成要剥离的URL的过程，那么您可能会忽略这些细微差别。但是，如果它们是从文档或网页收集的，或者是由人类输入的，则最好建议考虑如果您的代码遇到“不寻常”URL时可能发生的情况。

---

如果您关心的是构建URL对象所需的时间，请考虑使用URI对象。除此之外，URI对象不会尝试DNS查找主机名部分。

Answer 6

我写了一个方法（见下文），它提取一个url的域名，并使用简单的字符串匹配。它实际上做的是提取第一个"://"（或索引0，如果没有包含"://"）和第一个后续"/"（或索引String.length()，如果没有后续"/"）之间的位。其余的，前面的"www(_)*."位被切断。我相信会有这样的情况发生，但这在很多情况下应该足够好！

我读here的java.net.URI类可以做到这一点（并优先于java.net.URL类），但我遇到了与URI类的问题。值得注意的是，如果URL不包含该方案，即"http(s)"位，则URI.getHost()给出空值。

/** 
* Extracts the domain name from {@code url} 
* by means of String manipulation 
* rather than using the {@link URI} or {@link URL} class. 
* 
* @param url is non-null. 
* @return the domain name within {@code url}. 
*/ 
public String getUrlDomainName(String url) { 
    String domainName = new String(url); 

    int index = domainName.indexOf("://"); 

    if (index != -1) { 
    // keep everything after the "://" 
    domainName = domainName.substring(index + 3); 
    } 

    index = domainName.indexOf('/'); 

    if (index != -1) { 
    // keep everything before the '/' 
    domainName = domainName.substring(0, index); 
    } 

    // check for and remove a preceding 'www' 
    // followed by any sequence of characters (non-greedy) 
    // followed by a '.' 
    // from the beginning of the string 
    domainName = domainName.replaceFirst("^www.*?\\.", ""); 

    return domainName; 
} 

Answer 7

尝试使用方法：getDomainFromUrl（）在类

package com.visc.mobilesecurity.childrencare.utils; 

import android.content.Context; 

import com.visc.mobilesecurity.antitheft.backwardcompatibility.FroyoSupport; 
import com.visc.mobilesecurity.antitheft.util.AntiTheftUtils; 
import com.visc.mobilesecurity.constant.Key; 
import com.visc.mobilesecurity.util.Prefs; 

import org.json.JSONObject; 

import java.io.File; 
import java.io.FileOutputStream; 
import java.io.InputStream; 

/** 
* Created by thongnv12 on 3/9/2018. 
*/ 

public class ChildcareUtils { 

    public static final String[] NATION_DOMAIN = {"af", "ax", "al", "dz", "as", "ad", "ao", "ai", "aq", "ag", "ar", "am", "aw", "ac", "au", "at", "az", "bs", "bh", "bd", "bb", "eus", 
      "by", "be", "bz", "bj", "bm", "bt", "bo", "bq", "ba", "bw", "bv", "br", "io", "vg", "bn", "bg", "bf", "mm", "bi", "kh", "cm", "ca", "cv", "cat", "ky", "cf", "td", "cl", 
      "cn", "cx", "cc", "co", "km", "cd", "cg", "ck", "cr", "ci", "hr", "cu", "cw", "cy", "cz", "dk", "dj", "dm", "do", "tl", "ec", "eg", "sv", "gq", "er", "ee", "et", "eu", 
      "fk", "fo", "fm", "fj", "fi", "fr", "gf", "pf", "tf", "ga", "gal", "gm", "ps", "ge", "de", "gh", "gi", "gr", "gl", "gd", "gp", "gu", "gt", "gg", "gn", "gw", "gy", "ht", 
      "hm", "hn", "hk", "hu", "is", "in", "id", "ir", "iq", "ie", "im", "il", "it", "jm", "jp", "je", "jo", "kz", "ke", "ki", "kw", "kg", "la", "lv", "lb", "ls", "lr", "ly", 
      "li", "lt", "lu", "mo", "mk", "mg", "mw", "my", "mv", "ml", "mt", "mh", "mq", "mr", "mu", "yt", "mx", "md", "mc", "mn", "me", "ms", "ma", "mz", "mm", "na", "nr", "np", 
      "nl", "nc", "nz", "ni", "ne", "ng", "nu", "nf", "kp", "mp", "no", "om", "pk", "pw", "ps", "pa", "pg", "py", "pe", "ph", "pn", "pl", "pt", "pr", "qa", "ro", "ru", "rw", 
      "re", "bq", "bl", "sh", "kn", "lc", "mf", "fr", "pm", "vc", "ws", "sm", "st", "sa", "sn", "rs", "sc", "sl", "sg", "bq", "sx", "sk", "si", "sb", "so", "so", "za", "gs", 
      "kr", "ss", "es", "lk", "sd", "sr", "sj", "sz", "se", "ch", "sy", "tw", "tj", "tz", "th", "tg", "tk", "to", "tt", "tn", "tr", "tm", "tc", "tv", "ug", "ua", "ae", "uk", 
      "us", "vi", "uy", "uz", "vu", "va", "ve", "vn", "wf", "eh", "zm", "zw"}; 


    public static boolean isInNationString(String str) { 
     for (int index = 0; index < NATION_DOMAIN.length; index++) { 
      if (NATION_DOMAIN[index].equals(str)) { 
       return true; 
      } 
     } 
     return false; 
    } 


    public static String getDomainFromUrl(String urlStr) { 
     try { 
      String result = null; 
//   URL url = new URL(urlStr); 
//   result = url.getHost(); 
//   return result; 
// 
      // for test 
      // check dau cach 
      if (urlStr.contains(" ")) { 
       return null; 
      } 
      // replace 
      urlStr = urlStr.replace("https://", ""); 
      urlStr = urlStr.replace("http://", ""); 
      urlStr = urlStr.replace("www.", ""); 
      // 
      String[] splitStr = urlStr.split("/"); 

      String domainFull = splitStr[0]; 

      String[] splitDot = domainFull.split("\\."); 

      if (splitDot.length < 2) { 
       return null; 
      } 

      String nationStr = splitDot[splitDot.length - 1]; 

      if (isInNationString(nationStr)) { 
       if (splitDot.length < 4) { 
        result = domainFull; 
       } else { 
        StringBuilder strResult = new StringBuilder(); 
        int lengthDot = splitDot.length; 
        strResult.append(splitDot[lengthDot - 3]).append("."); 
        strResult.append(splitDot[lengthDot - 2]).append("."); 
        strResult.append(splitDot[lengthDot - 1]); 
        result = strResult.toString(); 
       } 

      } else { 
       if (splitDot.length < 3) { 
        result = domainFull; 
       } else { 
        StringBuilder strResult = new StringBuilder(); 
        int lengthDot = splitDot.length; 
        strResult.append(splitDot[lengthDot - 2]).append("."); 
        strResult.append(splitDot[lengthDot - 1]); 
        result = strResult.toString(); 
       } 
      } 
      return result; 
     } catch (Exception ex) { 
      ex.printStackTrace(); 
      return null; 
     } 

    } 
}