Java端HTTPDNS+Apache HttpClient最佳實務 - HTTPDNS

本文檔介紹在 Java 應用中使用 Apache HttpClient 接入 HTTPDNS 的方案。

1. 背景說明

Apache HttpClient 是 Java 生態中廣泛使用的 HTTP 網路程式庫，支援 4.x 和 5.x 兩個主要版本。通過實現 DnsResolver 介面，可以將 HTTPDNS 整合到 HttpClient 中。

2. 實現自訂 DnsResolver

HttpClient 5.x

import org.apache.hc.client5.http.DnsResolver;
import com.alibaba.sdk.java.httpdns.HttpDnsClient;
import com.alibaba.sdk.java.httpdns.HTTPDNSResult;
import com.alibaba.sdk.java.httpdns.RequestIpType;

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.List;

public class HttpDnsResolver implements DnsResolver {
    
    private final HttpDnsClient httpDnsClient;
    
    public HttpDnsResolver(HttpDnsClient httpDnsClient) {
        this.httpDnsClient = httpDnsClient;
    }

    @Override
    public String resolveCanonicalHostname(String host) {
        return host;
    }

    @Override
    public InetAddress[] resolve(String host) throws UnknownHostException {
        HTTPDNSResult result = httpDnsClient.getHttpDnsResultForHostSyncNonBlocking(host, RequestIpType.both);

        List<InetAddress> addresses = new ArrayList<>();
        try {
            if (result != null && result.getIps() != null) {
                for (String ip : result.getIps()) {
                    addresses.add(InetAddress.getByName(ip));
                }
            }
            if (result != null && result.getIpv6s() != null) {
                for (String ip : result.getIpv6s()) {
                    addresses.add(InetAddress.getByName(ip));
                }
            }
        } catch (UnknownHostException e) {
            // 忽略單個 IP 解析失敗
        }
        
        if (!addresses.isEmpty()) {
            return addresses.toArray(new InetAddress[0]);
        }
        
        // 降級到系統 DNS
        return InetAddress.getAllByName(host);
    }
}

HttpClient 4.x

import org.apache.http.conn.DnsResolver;
import com.alibaba.sdk.java.httpdns.HttpDnsClient;
import com.alibaba.sdk.java.httpdns.HTTPDNSResult;
import com.alibaba.sdk.java.httpdns.RequestIpType;

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.List;

public class HttpDnsResolver4 implements DnsResolver {
    
    private final HttpDnsClient httpDnsClient;
    
    public HttpDnsResolver4(HttpDnsClient httpDnsClient) {
        this.httpDnsClient = httpDnsClient;
    }

    @Override
    public InetAddress[] resolve(String host) throws UnknownHostException {
        HTTPDNSResult result = httpDnsClient.getHttpDnsResultForHostSyncNonBlocking(host, RequestIpType.both);

        List<InetAddress> addresses = new ArrayList<>();
        try {
            if (result != null && result.getIps() != null) {
                for (String ip : result.getIps()) {
                    addresses.add(InetAddress.getByName(ip));
                }
            }
            if (result != null && result.getIpv6s() != null) {
                for (String ip : result.getIpv6s()) {
                    addresses.add(InetAddress.getByName(ip));
                }
            }
        } catch (UnknownHostException e) {
            // 忽略單個 IP 解析失敗
        }
        
        if (!addresses.isEmpty()) {
            return addresses.toArray(new InetAddress[0]);
        }
        
        // 降級到系統 DNS
        return InetAddress.getAllByName(host);
    }
}

說明

4.x 和 5.x 的 DnsResolver 來自不同的包，5.x 需額外實現 resolveCanonicalHostname() 方法。

3. 配置 HttpClient

HttpClient 5.x

import org.apache.hc.client5.http.impl.classic.CloseableHttpClient;
import org.apache.hc.client5.http.impl.classic.HttpClients;
import org.apache.hc.client5.http.impl.io.PoolingHttpClientConnectionManagerBuilder;
import org.apache.hc.client5.http.io.HttpClientConnectionManager;

HttpDnsClient httpDnsClient = HttpDnsClient.getClient(accountId);

HttpClientConnectionManager connectionManager = PoolingHttpClientConnectionManagerBuilder.create()
    .setDnsResolver(new HttpDnsResolver(httpDnsClient))
    .build();

CloseableHttpClient httpClient = HttpClients.custom()
    .setConnectionManager(connectionManager)
    .build();

HttpClient 4.x

import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;

HttpDnsClient httpDnsClient = HttpDnsClient.getClient(accountId);

CloseableHttpClient httpClient = HttpClients.custom()
    .setDnsResolver(new HttpDnsResolver4(httpDnsClient))
    .build();

4. 總結

Apache HttpClient + HTTPDNS 的主要優勢：

實現簡單：只需實現 DnsResolver 介面即可接入
通用性強：在 HTTPS、SNI 以及設定 Cookie 等情境均適用，無需額外處理認證校正、網域名稱檢查等環節
版本相容：同時支援 HttpClient 4.x 和 5.x