获取 URL响应头的日期信息

以下实例演示了如何使用 HttpURLConnection 的 httpCon.getDate() 方法来获取 URL响应头的日期信息：

import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Date;
 
public class Main{
   public static void main(String args[]) 
   throws Exception {
      URL url = new URL("http://www.sanguo.com");
      HttpURLConnection httpCon = (HttpURLConnection) url.openConnection();
      long date = httpCon.getDate();
      if (date == 0)
          System.out.println("无法获取信息。");
      else
          System.out.println("Date: " + new Date(date));
   }
}

以上代码运行输出结果为：

Date: Mon May 04 11:57:06 CST 2015

获取 URL 响应头信息

以下实例演示了如何获取指定 URL 的响应头信息：

import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;
import java.util.Map;
import java.util.Set;
 
public class Main {
    public static void main(String[] args) throws IOException{
        URL url = new URL("http://www.sanguo.com");
        URLConnection conn = url.openConnection();
        
        Map headers = conn.getHeaderFields();
        Set<String> keys = headers.keySet();
        for( String key : keys ){
            String val = conn.getHeaderField(key);
            System.out.println(key+"    "+val);
        }
        System.out.println( conn.getLastModified() );
    }
}

以上代码运行输出结果为：

Transfer-Encoding    chunked
null    HTTP/1.1 200 OK
Server    Tengine/1.3.0
Connection    keep-alive
Vary    Cookie
Date    Mon, 04 May 2015 03:54:05 GMT
X-Pingback    http://www.sanguo.com/xmlrpc.php
X-Powered-By    PHP/5.3.15
Content-Type    text/html; charset=UTF-8

解析 URL

以下实例演示了如何使用 net.URL 类的 url.getProtocol() ,url.getFile() 等方法来解析 URL 地址：

import java.net.URL;
 
public class Main {
   public static void main(String[] args) 
   throws Exception {
      URL url = new URL("http://www.sanguo.com/html/html-tutorial.html");
      System.out.println("URL 是 " + url.toString());
      System.out.println("协议是 " + url.getProtocol());
      System.out.println("文件名是 " + url.getFile());
      System.out.println("主机是 " + url.getHost());
      System.out.println("路径是 " + url.getPath());
      System.out.println("端口号是 " + url.getPort());
      System.out.println("默认端口号是 " 
      + url.getDefaultPort());
   }
}

以上代码运行输出结果为：

URL 是 http://www.sanguo.com/html/html-tutorial.html
协议是 http
文件名是 /html/html-tutorial.html
主机是 www.sanguo.com
路径是 /html/html-tutorial.html
端口号是 -1
默认端口号是 80

ServerSocket 和 Socket 通信实例

1、建立服务器端

• 服务器建立通信ServerSocket
• 服务器建立Socket接收客户端连接
• 建立IO输入流读取客户端发送的数据
• 建立IO输出流向客户端发送数据消息

服务器端代码:

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.ServerSocket;
import java.net.Socket;
 
public class Server {
   public static void main(String[] args) {
      try {
         ServerSocket ss = new ServerSocket(8888);
         System.out.println("启动服务器....");
         Socket s = ss.accept();
         System.out.println("客户端:"+s.getInetAddress().getLocalHost()+"已连接到服务器");
         
         BufferedReader br = new BufferedReader(new InputStreamReader(s.getInputStream()));
         //读取客户端发送来的消息
         String mess = br.readLine();
         System.out.println("客户端："+mess);
         BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
         bw.write(mess+"\n");
         bw.flush();
      } catch (IOException e) {
         e.printStackTrace();
      }
   }
}

以上代码运行输出结果为：

启动服务器....

2、建立客户端

• 创建Socket通信，设置通信服务器的IP和Port
• 建立IO输出流向服务器发送数据消息
• 建立IO输入流读取服务器发送来的数据消息

客户端代码:

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.Socket;
import java.net.UnknownHostException;
 
public class Client {
   public static void main(String[] args) {
      try {
         Socket s = new Socket("127.0.0.1",8888);
         
         //构建IO
         InputStream is = s.getInputStream();
         OutputStream os = s.getOutputStream();
         
         BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(os));
         //向服务器端发送一条消息
         bw.write("测试客户端和服务器通信，服务器接收到消息返回到客户端\n");
         bw.flush();
         
         //读取服务器返回的消息
         BufferedReader br = new BufferedReader(new InputStreamReader(is));
         String mess = br.readLine();
         System.out.println("服务器："+mess);
      } catch (UnknownHostException e) {
         e.printStackTrace();
      } catch (IOException e) {
         e.printStackTrace();
      }
   }
}

以上代码运行输出结果为：

服务器：测试客户端和服务器通信，服务器接收到消息返回到客户端