InetAddress 类详解

`InetAddress` 类详解

一、核心作用

封装 IP 地址：同时支持 IPv4 和 IPv6 地址
域名解析：将域名转换为 IP 地址（DNS 查询）
地址验证：检查网络地址的有效性
无构造方法：通过静态工厂方法获取实例

二、核心方法

方法	作用描述
`static InetAddress getByName(String host)`	通过主机名/IP字符串获取实例（可能触发DNS查询）
`static InetAddress[] getAllByName(String host)`	获取主机的所有IP地址
`static InetAddress getLocalHost()`	获取本地主机地址
`String getHostName()`	获取主机名（可能触发反向DNS查询）
`String getHostAddress()`	获取IP地址字符串
`boolean isReachable(int timeout)`	测试地址可达性（ICMP ping）

三、基础使用示例

1. 获取单个地址

import java.net.InetAddress;
import java.net.UnknownHostException;public class InetAddressDemo {public static void main(String[] args) {try {// 通过域名获取InetAddress googleAddr = InetAddress.getByName("www.google.com");System.out.println("Google IP: " + googleAddr.getHostAddress());System.out.println("Host Name: " + googleAddr.getHostName());// 通过IP地址获取InetAddress ipAddr = InetAddress.getByName("142.250.179.196");System.out.println("Host for 142.250.179.196: " + ipAddr.getHostName());} catch (UnknownHostException e) {System.err.println("Address resolution failed: " + e.getMessage());}}
}

2. 获取所有地址（多IP场景）

// 获取某个域名的所有IP地址
try {InetAddress[] baiduAddrs = InetAddress.getAllByName("www.baidu.com");System.out.println("\nBaidu IPs:");for (InetAddress addr : baiduAddrs) {System.out.println(" - " + addr.getHostAddress());}
} catch (UnknownHostException e) {e.printStackTrace();
}

3. 获取本机地址

try {InetAddress localHost = InetAddress.getLocalHost();System.out.println("\nLocal Host:");System.out.println("Name: " + localHost.getHostName());System.out.println("IP: " + localHost.getHostAddress());
} catch (UnknownHostException e) {e.printStackTrace();
}

四、运行结果示例

Google IP: 142.250.179.196
Host Name: www.google.com
Host for 142.250.179.196: fra24s01-in-f4.1e100.netBaidu IPs:- 110.242.68.3- 110.242.68.4Local Host:
Name: My-Computer.local
IP: 192.168.1.100

五、特殊地址处理

1. 回环地址验证

InetAddress loopback = InetAddress.getByName("localhost");
System.out.println("Is loopback: " + loopback.isLoopbackAddress()); // true

2. IPv6 地址处理

InetAddress ipv6Addr = InetAddress.getByName("2001:4860:4860::8888");
System.out.println("IPv6 Address: " + ipv6Addr.getHostAddress());

3. 地址可达性测试

InetAddress target = InetAddress.getByName("www.github.com");
boolean reachable = target.isReachable(5000); // 5秒超时
System.out.println("Is reachable: " + reachable);

六、注意事项

DNS 查询开销：
- getHostName() 可能触发反向 DNS 查询
- 频繁调用需考虑性能影响
缓存机制：
- JVM 默认缓存 DNS 查询结果
- 缓存时间由 networkaddress.cache.ttl 属性控制
异常处理：
- 必须捕获 UnknownHostException
- 常见触发场景：
  - 无效域名
  - 无网络连接
  - DNS 服务器不可达
IPv4/IPv6 兼容性：
- 优先使用系统默认协议栈
- 可通过 JVM 参数控制：
```
-Djava.net.preferIPv4Stack=true
-Djava.net.preferIPv6Addresses=true
```

七、实际应用场景

1. 验证 IP 地址格式

public static boolean isValidIP(String ip) {try {InetAddress.getByName(ip);return true;} catch (UnknownHostException e) {return false;}
}

2. 获取本机真实 IP（非回环地址）

public static String getRealLocalIP() {try {return InetAddress.getLocalHost().getHostAddress();} catch (UnknownHostException e) {return "127.0.0.1";}
}

3. 批量地址解析

public static void resolveAddresses(List<String> hosts) {hosts.forEach(host -> {try {InetAddress[] addresses = InetAddress.getAllByName(host);System.out.println(host + " : " + Arrays.stream(addresses).map(InetAddress::getHostAddress).collect(Collectors.joining(", ")));} catch (UnknownHostException e) {System.err.println("Cannot resolve: " + host);}});
}

八、与 `NetworkInterface` 结合使用

import java.net.NetworkInterface;
import java.util.Enumeration;// 获取本机所有网络接口的IP地址
public static void listAllIPs() {try {Enumeration<NetworkInterface> interfaces = NetworkInterface.getNetworkInterfaces();while (interfaces.hasMoreElements()) {NetworkInterface ni = interfaces.nextElement();Enumeration<InetAddress> addresses = ni.getInetAddresses();while (addresses.hasMoreElements()) {InetAddress addr = addresses.nextElement();System.out.println(ni.getName() + " : " + addr.getHostAddress());}}} catch (Exception e) {e.printStackTrace();}
}