Java网络编程核心实战详解
你提供的代码清单展示了 Java 网络编程的核心类和方法。以下是这些方法的分类、对比和关键代码示例。一、核心操作分类与对比操作类型核心类/接口关键方法/特性适用场景IP地址与主机名解析InetAddressgetLocalHost(),getByName(),getAllByName()获取本地或远程主机的IP地址信息TCP Socket通信Socket,ServerSocketSocket(String host, int port),getInputStream(),getOutputStream()面向连接的、可靠的、基于流的网络通信如HTTP、FTPURL 解析与访问URL,URLConnection,HttpURLConnectionURL(String spec),openConnection(),getHeaderFields()解析URL结构建立HTTP/HTTPS连接并获取资源UDP 数据报通信DatagramSocket,DatagramPacketDatagramSocket(int port),send(DatagramPacket p),receive(DatagramPacket p)无连接的、不可靠的、基于数据包的网络通信如DNS、音视频流二、关键代码示例1. 使用 InetAddress 获取网络地址信息InetAddress类用于表示IP地址IPv4或IPv6并提供了获取主机名和IP地址的方法。// 对应 listing 1 import java.net.InetAddress; import java.net.UnknownHostException; public class InetAddressExample { public static void main(String[] args) throws UnknownHostException { // 获取本机地址 InetAddress localAddress InetAddress.getLocalHost(); System.out.println(Local Host: localAddress); // 通过主机名获取单个IP地址 InetAddress remoteAddress InetAddress.getByName(www.example.com); System.out.println(Single Address for www.example.com: remoteAddress); // 通过主机名获取所有IP地址适用于有多个IP的主机如负载均衡 InetAddress[] allAddresses InetAddress.getAllByName(www.google.com); System.out.println(All Addresses for www.google.com:); for (InetAddress addr : allAddresses) { System.out.println( addr); } } }2. 使用 Socket 进行 TCP 客户端通信Socket类用于建立到服务器的TCP连接并通过流进行数据读写。// 对应 listing 2 (TCP客户端示例) import java.io.*; import java.net.*; public class TcpClientExample { public static void main(String[] args) throws Exception { String host whois.internic.net; int port 43; // Whois服务标准端口 String query (args.length 0) ? example.com : args[0]; // 1. 创建Socket连接到服务器 try (Socket socket new Socket(host, port)) { // 2. 获取输入输出流 InputStream in socket.getInputStream(); OutputStream out socket.getOutputStream(); // 3. 发送请求数据 String request query ; out.write(request.getBytes()); out.flush(); // 确保数据发送 // 4. 读取服务器响应 BufferedReader reader new BufferedReader(new InputStreamReader(in)); String line; while ((line reader.readLine()) ! null) { System.out.println(line); } } // try-with-resources 自动关闭Socket } }3. 使用 URL 和 URLConnection 访问网络资源URL类用于解析URLURLConnection用于建立连接并获取元数据和内容。// 综合 listing 3, 4, 5 的要点 import java.net.*; import java.io.*; import java.util.Date; import java.util.Map; import java.util.List; public class UrlConnectionExample { public static void main(String[] args) throws Exception { URL url new URL(https://httpbin.org/get); // 打开连接 (通用URLConnection) URLConnection connection url.openConnection(); // 如果是HTTP/HTTPS可以转换为HttpURLConnection以使用HTTP特有方法 if (connection instanceof HttpURLConnection) { HttpURLConnection httpConn (HttpURLConnection) connection; httpConn.setRequestMethod(GET); httpConn.setConnectTimeout(5000); // 设置连接超时 httpConn.setReadTimeout(5000); // 设置读取超时 // 获取HTTP响应信息 System.out.println(Response Code: httpConn.getResponseCode()); System.out.println(Response Message: httpConn.getResponseMessage()); // 获取所有响应头 MapString, ListString headers httpConn.getHeaderFields(); for (Map.EntryString, ListString entry : headers.entrySet()) { System.out.println(entry.getKey() : entry.getValue()); } } // 获取连接通用信息 (listing 4) System.out.println(Content-Type: connection.getContentType()); System.out.println(Content-Length: connection.getContentLengthLong()); long lastModified connection.getLastModified(); if (lastModified ! 0) { System.out.println(Last-Modified: new Date(lastModified)); } // 读取响应内容 try (BufferedReader reader new BufferedReader( new InputStreamReader(connection.getInputStream()))) { String line; System.out.println( Response Body ); while ((line reader.readLine()) ! null) { System.out.println(line); } } } }4. 使用 DatagramSocket 进行 UDP 通信DatagramSocket和DatagramPacket用于无连接的UDP通信数据以数据包形式发送和接收。// 对应 listing 6 (UDP 客户端/服务器示例) import java.net.*; public class UdpExample { // 服务器端方法 public static void startServer(int port) throws Exception { try (DatagramSocket socket new DatagramSocket(port)) { System.out.println(UDP Server started on port port); byte[] buffer new byte[1024]; while (true) { // 1. 创建数据包用于接收数据 DatagramPacket packet new DatagramPacket(buffer, buffer.length); // 2. 接收数据包 (阻塞方法) socket.receive(packet); // 3. 处理接收到的数据 String received new String(packet.getData(), 0, packet.getLength()); InetAddress clientAddress packet.getAddress(); int clientPort packet.getPort(); System.out.printf(Received from %s:%d - %s%n, clientAddress.getHostAddress(), clientPort, received); // 4. 准备响应数据 String response Echo: received; byte[] responseData response.getBytes(); DatagramPacket responsePacket new DatagramPacket( responseData, responseData.length, clientAddress, clientPort); // 5. 发送响应 socket.send(responsePacket); } } } // 客户端方法 public static void startClient(String serverHost, int serverPort) throws Exception { try (DatagramSocket socket new DatagramSocket()) { InetAddress serverAddress InetAddress.getByName(serverHost); String message Hello UDP Server!; byte[] sendData message.getBytes(); // 1. 创建并发送数据包 DatagramPacket sendPacket new DatagramPacket( sendData, sendData.length, serverAddress, serverPort); socket.send(sendPacket); System.out.println(Sent: message); // 2. 准备接收响应 byte[] receiveData new byte[1024]; DatagramPacket receivePacket new DatagramPacket(receiveData, receiveData.length); socket.receive(receivePacket); // 设置超时: socket.setSoTimeout(5000); // 3. 处理响应 String response new String(receivePacket.getData(), 0, receivePacket.getLength()); System.out.println(Received: response); } } public static void main(String[] args) throws Exception { if (args.length 0 args[0].equals(server)) { startServer(9876); } else { startClient(localhost, 9876); } } }三、核心要点总结InetAddress用于IP地址和主机名的相互解析不涉及网络连接本身。TCP vs UDPTCP (Socket/ServerSocket)面向连接、可靠、基于字节流。适用于需要可靠数据传输的场景如网页浏览(HTTP)、文件传输(FTP)、电子邮件(SMTP)。UDP (DatagramSocket/DatagramPacket)无连接、不可靠、基于数据报。适用于对实时性要求高、能容忍少量丢包的场景如视频流、DNS查询、在线游戏。URL 处理URL类ruchtig解析URL字符串URLConnection提供了建立连接、读取响应头和内容的通用方法。对于HTTP/HTTPS使用其子类HttpURLConnection可以访问HTTP特有的功能如请求方法、响应码等。资源管理网络连接Socket、URLConnection、流InputStream、OutputStream都是需要关闭的系统资源。务必使用try-with-resources语句或在finally块中确保它们被关闭以避免资源泄漏。异常处理网络操作可能抛出多种受检异常如UnknownHostException、SocketException、IOException、MalformedURLException等必须进行妥善处理。参考来源Java网络编程Socket、URLConnectionjava 网络编程基础_Java网络编程基础一java.net 包详解Java之网络编程Java基础——网络编程(Socket编程)
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