百度找java获取本机的外网IP地址都是以前的垃圾代码，别人页面都改了，怎么拿得到。

之前学过python的爬虫，拿外网ip简单就是通过 https://ip.chinaz.com/这个网站去得到。

百度习惯了，md ！还百度了半天。

//代码拿去，有一说一效率有点低
/**
 * 得到本机的外网的外网IP地址 作为该局域网的区分标志
 * @return
 */
public static String getIp() {
    Document document = null;
    try {
        document = Jsoup.connect("https://ip.chinaz.com/").get();
    } catch (IOException e) {
        e.printStackTrace();
    }
    Elements select = document.select("#leftinfo > div.IcpMain02.bor-t1s02 > div.WhoIpWrap.jspu > div.WhwtdWrap.bor-b1s.col-gray03 > span:nth-child(1)");
    String s = select.toString();
    String ip = s.substring(s.indexOf(">") + 1, s.lastIndexOf("<"));
    return ip;
}

//另一种方法，找到的有效：

 public static String getIP()  {
        String ip = "http://pv.sohu.com/cityjson?ie=utf-8";
        String inputLine = "";
        String read = "";
        String toIp="";
        try {
            URL url = new URL(ip);
            HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
            BufferedReader in = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
            while ((read = in.readLine()) != null) {
                inputLine += read;
            }
            String ObjJson=inputLine.substring(inputLine.indexOf("=")+1,inputLine.length()-1);
//            System.out.println(ObjJson);
            JSONObject jsonObj= JSON.parseObject(ObjJson);
            toIp=jsonObj.getString("cip");
//            throw new Exception();
        } catch (Exception e) {
            toIp="";
        }
        return toIp;
    }


 /**
     * 根据域名获取ip地址
     */
    public static String getIfIP() {
        String toIp="";
        try{
            String pathName="baidu.com";//这里没有进行支持https协议的，可以自行进行切割字符串
            InetAddress address =InetAddress.getAllByName(pathName)[0];
            toIp=address.getHostAddress();
        }catch (Exception e){
            toIp="";
        }
        return toIp;
    }

原理

通过 HTTP 访问第三方获取 IP 的服务接口获取本机的外网 IP，例如：

• http://checkip.amazonaws.com/
• https://ipv4.icanhazip.com/
• http://bot.whatismyipaddress.com/
• 等等…

考虑到这些第三方接口不一定 100% 稳定，例如可能出现下线、错误、访问超时或太慢的情况，所以不能仅依赖其中之一。

下面提供一种方案，并发访问这些服务接口，并返回第一个成功的结果，也就是其中最快的一个返回结果。

实现

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.*;
import java.util.regex.Pattern;

public class ExternalIPUtil {

    /**
     * IP 地址校验的正则表达式
     */
    private static final Pattern IPV4_PATTERN = Pattern.compile("^(([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.){3}([01]?\\d\\d?|2[0-4]\\d|25[0-5])$");

    /**
     * 获取 IP 地址的服务列表
     */
    private static final String[] IPV4_SERVICES = {
            "http://checkip.amazonaws.com/",
            "https://ipv4.icanhazip.com/",
            "http://bot.whatismyipaddress.com/"
            // and so on ...
    };

    public static String get() throws ExecutionException, InterruptedException {
        List<Callable<String>> callables = new ArrayList<>();
        for (String ipService : IPV4_SERVICES) {
            callables.add(() -> get(ipService));
        }

        ExecutorService executorService = Executors.newCachedThreadPool();
        try {
            // 返回第一个成功获取的 IP
            return executorService.invokeAny(callables);
        } finally {
            executorService.shutdown();
        }
    }

    private static String get(String url) throws IOException {
        try (BufferedReader in = new BufferedReader(new InputStreamReader(new URL(url).openStream()))) {
            String ip = in.readLine();
            if (IPV4_PATTERN.matcher(ip).matches()) {
                return ip;
            } else {
                throw new IOException("invalid IPv4 address: " + ip);
            }
        }
    }
}

线程池的 ExecutorService.invokeAny(callables) 方法用于并发执行多个线程，并拿到最快的执行成功的线程的返回值，只要有一个执行成功，其他失败的任务都会忽略。但是如果全部失败，例如本机根本就没有连外网，那么就会抛出 ExecutionException 异常。

Gist

https://gist.github.com/wucao/811e0bbe08f2dfab527a065d052d12a5

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获取本机的外网地址 

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package untils;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.*;
import java.util.Enumeration;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * @author CBeann
 * @create 2020-04-13 1:31
 */
public class IPUntils {

    public static void main(String[] args) throws Exception {
        System.out.println(IPUntils.getInterIP1());
        System.out.println(IPUntils.getInterIP2());
        System.out.println(IPUntils.getOutIPV4());
    }

    public static String getInterIP1() throws Exception {
        return InetAddress.getLocalHost().getHostAddress();
    }

    public static String getInterIP2() throws SocketException {
        String localip = null;// 本地IP，如果没有配置外网IP则返回它
        String netip = null;// 外网IP
        Enumeration<NetworkInterface> netInterfaces;
        netInterfaces = NetworkInterface.getNetworkInterfaces();
        InetAddress ip = null;
        boolean finded = false;// 是否找到外网IP
        while (netInterfaces.hasMoreElements() && !finded) {
            NetworkInterface ni = netInterfaces.nextElement();
            Enumeration<InetAddress> address = ni.getInetAddresses();
            while (address.hasMoreElements()) {
                ip = address.nextElement();
                if (!ip.isSiteLocalAddress() && !ip.isLoopbackAddress() && ip.getHostAddress().indexOf(":") == -1) {// 外网IP
                    netip = ip.getHostAddress();
                    finded = true;
                    break;
                } else if (ip.isSiteLocalAddress() && !ip.isLoopbackAddress() && ip.getHostAddress().indexOf(":") == -1) {// 内网IP
                    localip = ip.getHostAddress();
                }
            }
        }
        if (netip != null && !"".equals(netip)) {
            return netip;
        } else {
            return localip;
        }
    }

    public static String getOutIPV4() {
        String ip = "";
        String chinaz = "http://ip.chinaz.com";

        StringBuilder inputLine = new StringBuilder();
        String read = "";
        URL url = null;
        HttpURLConnection urlConnection = null;
        BufferedReader in = null;
        try {
            url = new URL(chinaz);
            urlConnection = (HttpURLConnection) url.openConnection();
            in = new BufferedReader(new InputStreamReader(urlConnection.getInputStream(), "UTF-8"));
            while ((read = in.readLine()) != null) {
                inputLine.append(read + "\r\n");
            }
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (in != null) {
                try {
                    in.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        Pattern p = Pattern.compile("\\<dd class\\=\"fz24\">(.*?)\\<\\/dd>");
        Matcher m = p.matcher(inputLine.toString());
        if (m.find()) {
            String ipstr = m.group(1);
            ip = ipstr;
        }
        return ip;
    }
}