获取本机外网IP的工具类

ExternalIpAddressFetcher.java

package com.tyust.common;
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;  
  
/** 
 * 获取本机外网IP地址 
 * 思想是访问网站http://checkip.dyndns.org/，得到返回的文本后解析出本机在外网的IP地址 
 * @author Administrator 
 * 
 */  
public class ExternalIpAddressFetcher {  
    // 外网IP提供者的网址  
    private String externalIpProviderUrl;  
  
    // 本机外网IP地址  
    private String myExternalIpAddress;  
  
    public ExternalIpAddressFetcher(String externalIpProviderUrl) {  
        this.externalIpProviderUrl = externalIpProviderUrl;  
  
        String returnedhtml = fetchExternalIpProviderHTML(externalIpProviderUrl);  
          
        parse(returnedhtml);  
    }  
  
    /** 
     * 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 Address: 123.147.226.222</body></html> 
     * @param externalIpProviderUrl 
     * @return 
     */  
    private String fetchExternalIpProviderHTML(String externalIpProviderUrl) {  
        // 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");  
              
            // 返回  
            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()){  
            myExternalIpAddress=matcher.group(0);  
        }      
    }      
  
    /** 
     * 得到本机外网地址,得不到则为空 
     * @return 
     */  
    public String getMyExternalIpAddress() {  
        return myExternalIpAddress;  
    }  
      
    public static void main(String[] args){  
        ExternalIpAddressFetcher fetcher=new ExternalIpAddressFetcher("http://checkip.dyndns.org/");  
          
        System.out.println(fetcher.getMyExternalIpAddress());  
    }  
}