Java 示例 - 查找代理设置

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  问题描述

  如何查找系统的代理设置？
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  解决方案

  以下示例显示了如何使用 systemSetting 的 put 方法和 HttpURLConnection 类的 getResponse 方法在系统上查找代理设置和创建代理连接。

  
  import java.net.HttpURLConnection;
  import java.net.URL;
  import java.util.Properties;
  import java.net.InetSocketAddress;
  import java.net.Proxy;
  import java.net.ProxySelector;
  import java.net.URI;
  public class Main{
     public static void main(String s[]) throws Exception {
        try {
           Properties systemSettings = System.getProperties();
           systemSettings.put("proxySet", "true");
           systemSettings.put("http.proxyHost", "proxy.mycompany1.local");
           systemSettings.put("http.proxyPort", "80");
           
           URL u = new URL("http://www.google.com");
           HttpURLConnection con = (HttpURLConnection)u.openConnection();
           System.out.println(con.getResponseCode() + " : " + con.getResponseMessage());
           System.out.println(con.getResponseCode() == HttpURLConnection.HTTP_OK);
        } catch (Exception e) {
           e.printStackTrace();
           System.out.println(false);
        }
        System.setProperty("java.net.useSystemProxies", "true");
        Proxy proxy = (Proxy) ProxySelector.getDefault().select(new URI(
           "http://www.yahoo.com/")).iterator().
        next();;
        System.out.println("proxy hostname : " + proxy.type());
        InetSocketAddress addr = (InetSocketAddress)proxy.address();
        
        if (addr == null) {
           System.out.println("No Proxy");
        } else {
           System.out.println("proxy hostname : " + addr.getHostName());
           System.out.println("proxy port : " + addr.getPort());
        }
     }
  }
  

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  结果

  上面的代码示例将产生以下结果。

  
  200 : OK
  true
  proxy hostname : HTTP
  proxy hostname : proxy.mycompany1.local
  proxy port : 80
  

  以下是查找系统代理设置的示例？

  
  import java.net.InetSocketAddress;
  import java.net.Proxy;
  import java.net.ProxySelector;
  import java.net.URI;
  import java.util.Iterator;
  import java.util.List;
  public class NewClass {
     public static void main(String[] args) {
        try {
           System.setProperty("java.net.useSystemProxies", "true");
           List<Proxy> l = ProxySelector.getDefault().select(
              new URI("http://www.google.com/"));
           
           for (Iterator<Proxy> iter = l.iterator(); iter.hasNext();) {
              Proxy proxy = iter.next();
              System.out.println("proxy hostname : " + proxy.type());
              InetSocketAddress addr = (InetSocketAddress) proxy.address();
              
              if (addr == null) {
                 System.out.println("No Proxy");
              } else {
                 System.out.println("proxy hostname : " + addr.getHostName());
                 System.out.println("proxy port : " + addr.getPort());
              } 
           }
        } catch (Exception e) {
           e.printStackTrace();
        }
     }
  }
  

  上面的代码示例将产生以下结果。

  
  proxy hostname : DIRECT
  No Proxy