java获取本机外网IP地址-优快云博客

本文链接：https://blog.youkuaiyun.com/seven_tao/article/details/9196485

本文介绍了一个Java程序，用于从特定网站抓取HTML内容并从中解析出本机的外网IP地址。通过发送HTTP请求获取包含IP信息的网页，再利用正则表达式提取IP。

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package ip.test;

import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class IPUtil {
	// 外网IP提供者的网址
	private String externalIpProviderUrl;
	// 本机外网IP地址
	private String IPAddress;

	public String getIPAddress() {
		return IPAddress;
	}

	public IPUtil(String externalIpProviderUrl) {
		this.externalIpProviderUrl = externalIpProviderUrl;
		String returnedhtml = fetchExternalIpProviderHTML();
		parse(returnedhtml);
	}

	public static void main(String[] args) {
		IPUtil fetcher = new IPUtil("http://checkip.dyndns.org/");
		System.out.println(fetcher.getIPAddress());
	}

	/**
	 * 从外网提供者处获得包含本机外网地址的字符串 从http://checkip.dyndns.org返回的字符串如下
	 * <html><head><title>Current IP Check</title></head><body>Current IP
	 * @return
	 */
	private String fetchExternalIpProviderHTML() {
		// 输入流
		InputStream in = null;
		// 到外网提供者的Http连接
		HttpURLConnection httpConn = null;
		try {
			// 打开连接
			URL url = new URL(externalIpProviderUrl);
			httpConn = (HttpURLConnection) url.openConnection();
			// 连接设置
			HttpURLConnection.setFollowRedirects(true);
			httpConn.setRequestMethod("GET");
			httpConn.setRequestProperty("User-Agent",
					"Mozilla/4.0 (compatible; MSIE 6.0; Windows 2000)");
			// 获取连接的输入流
			in = httpConn.getInputStream();
			byte[] bytes = new byte[1024];// 此大小可根据实际情况调整
			// 读取到数组中
			int offset = 0;
			int numRead = 0;
			while (offset < bytes.length
					&& (numRead = in.read(bytes, offset, bytes.length - offset)) >= 0) {
				offset += numRead;
			}
			// 将字节转化为为UTF-8的字符串
			String receivedString = new String(bytes, "UTF-8");
			System.out.println("xml的内容:" + receivedString);
			return receivedString;
		} catch (MalformedURLException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			try {
				in.close();
				httpConn.disconnect();
			} catch (Exception ex) {
				ex.printStackTrace();
			}
		}

		// 出现异常则返回空
		return null;
	}

	/**
	 * 使用正则表达式解析返回的HTML文本,得到本机外网地址
	 * 
	 * @param html
	 */
	private void parse(String html) {
		Pattern pattern = Pattern.compile(
				"(\\d{1,3})[.](\\d{1,3})[.](\\d{1,3})[.](\\d{1,3})",
				Pattern.CASE_INSENSITIVE);
		Matcher matcher = pattern.matcher(html);
		while (matcher.find()) {
			IPAddress = matcher.group(0);
		}
		System.out.println("解析得到的外网IP:" + IPAddress);
	}
}