轻松掌握：Java中获取请求IP地址的6种实用方法及实战案例

在Java开发中，获取请求的IP地址是一个常见的需求，无论是用于用户地理位置分析、安全控制还是其他业务逻辑。下面，我将详细介绍六种在Java中获取请求IP地址的实用方法，并结合实战案例进行说明。

方法一：使用HttpServletRequest对象

这是最直接的方法，通过HttpServletRequest对象获取IP地址。

import javax.servlet.http.HttpServletRequest;

public String getIpAddress(HttpServletRequest request) {
    String ip = request.getHeader("X-Forwarded-For");
    if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
        ip = request.getHeader("Proxy-Client-IP");
    }
    if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
        ip = request.getHeader("WL-Proxy-Client-IP");
    }
    if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
        ip = request.getHeader("HTTP_CLIENT_IP");
    }
    if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
        ip = request.getHeader("HTTP_X_FORWARDED_FOR");
    }
    if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
        ip = request.getRemoteAddr();
    }
    return ip;
}

实战案例：在Spring MVC的Controller中，使用上述方法获取用户IP地址。

@Controller
public class UserController {

    @RequestMapping("/user/ip")
    public String getUserIp(HttpServletRequest request) {
        String ip = getIpAddress(request);
        return "User IP: " + ip;
    }
}

方法二：使用RequestContextHolder

在Spring框架中，可以使用RequestContextHolder获取当前线程的HttpServletRequest对象。

import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;

public String getIpAddress() {
    ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
    HttpServletRequest request = attributes.getRequest();
    return getIpAddress(request);
}

方法三：使用Apache Commons HttpClient

Apache Commons HttpClient库提供了方便的API来处理HTTP请求，其中包括获取IP地址。

import org.apache.http.HttpEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

public String getIpAddress(String url) {
    CloseableHttpClient httpClient = HttpClients.createDefault();
    HttpGet httpGet = new HttpGet(url);
    try (CloseableHttpResponse response = httpClient.execute(httpGet)) {
        HttpEntity entity = response.getEntity();
        if (entity != null) {
            return EntityUtils.toString(entity, "UTF-8");
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
    return null;
}

方法四：使用Java网络API

Java的网络API也提供了获取IP地址的方法。

import java.net.InetAddress;
import java.net.UnknownHostException;

public String getIpAddress() {
    try {
        return InetAddress.getLocalHost().getHostAddress();
    } catch (UnknownHostException e) {
        e.printStackTrace();
        return null;
    }
}

方法五：使用Nginx反向代理

在Nginx中配置反向代理，并在Nginx服务器上获取真实IP地址。

location / {
    proxy_pass http://backend;
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}

方法六：使用第三方服务

可以使用第三方服务，如IP138、IPInfo等，通过API获取IP地址信息。

import java.net.HttpURLConnection;
import java.net.URL;
import java.io.BufferedReader;
import java.io.InputStreamReader;

public String getIpAddress(String ip) {
    try {
        URL url = new URL("http://ip138.com/ip.asp?ip=" + ip);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setRequestMethod("GET");
        BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream(), "UTF-8"));
        StringBuilder result = new StringBuilder();
        String line;
        while ((line = reader.readLine()) != null) {
            result.append(line);
        }
        reader.close();
        return result.toString();
    } catch (Exception e) {
        e.printStackTrace();
        return null;
    }
}

以上是Java中获取请求IP地址的六种实用方法及实战案例。在实际应用中，可以根据具体需求选择合适的方法。