import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.conn.ClientConnectionOperator;
import org.apache.http.conn.DnsResolver;
import org.apache.http.conn.scheme.SchemeRegistry;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.impl.conn.BasicClientConnectionManager;
import org.apache.http.impl.conn.DefaultClientConnectionOperator;

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.HashMap;
import java.util.Map;

/**
 * 在 httpclient 4.2 中使用自定义的 DNS 解析
 */
public class CustomDnsResolverDemo {

    public static void main(String[] args) throws Exception {

        // 创建自定义的 ConnectionManager
        BasicClientConnectionManager connectionManager = new BasicClientConnectionManager() {

            @Override
            protected ClientConnectionOperator createConnectionOperator(SchemeRegistry schreg) {
                return new DefaultClientConnectionOperator(schreg, new MyDnsResolver());
            }
        };

        // 创建 HttpClient 对象
        DefaultHttpClient httpclient = new DefaultHttpClient(connectionManager);

        // 构造请求
        HttpGet httpget = new HttpGet("https://www.google.com/");
        System.out.println(httpget.getRequestLine());

        // 发送请求并返回结果
        HttpResponse response = httpclient.execute(httpget);
        System.out.println(response.getEntity().getContentType());
        System.out.println(response.getStatusLine());

        // 这句不是必须的，只是让程序结束更快点
        httpclient.getConnectionManager().shutdown();
    }

    // 自定义的 DNS 解析类
    private static class MyDnsResolver implements DnsResolver {

        private static final Map<String, InetAddress[]> MAPPINGS = new HashMap<String, InetAddress[]>();

        static {
            addResolve("www.google.com", "74.125.134.138");
        }

        private static void addResolve(String host, String ip) {
            try {
                MAPPINGS.put(host, new InetAddress[]{InetAddress.getByName(ip)});
            } catch (UnknownHostException e) {
                e.printStackTrace();
            }
        }

        @Override
        public InetAddress[] resolve(String host) throws UnknownHostException {
            return MAPPINGS.containsKey(host) ? MAPPINGS.get(host) : new InetAddress[0];
        }
    }
}