Apache HttpClient 4.3.3 如何查找请求站点的目标IP

Question

我读过这个：

http://httpcomponents.10934.n7.nabble.com/get-InetAddress-for-the-HTTP-TARGET-HOST-td18332.html

而且我不知道如何使用最新的 Apache HttpClient 4.3.3 做同样的事情。我想要做的是获取请求站点的IP。我知道使用最小的 httpclient 是不可能的，但是应该如何使用它？

由于最小的 httpclient 将 PoolingHttpClientConnectionManager(HttpClientConnectionManager) 作为参数而不是 ClientConnectionManager 我不知道要覆盖哪些方法以及要设置哪些属性。上面的示例可以直接访问套接字，而新的则不是这种情况。

所以问题是如何使用新的 (4.3.3) API 做到这一点。以及如何正确地防止已解析的 IP 被重定向，例如避免二次 DNS 解析。

还有一个代码片段，它近似于链接中所写的内容，并且两行输出都是 NULL：

 public static void main(String[] args) throws ClientProtocolException,
            IOException {

        String s = "http://google.com";

        PoolingHttpClientConnectionManager m = new PoolingHttpClientConnectionManager(
                RegistryBuilder.<ConnectionSocketFactory> create()
                        .register("http", new PlainConnectionSocketFactory() {

                            @Override
                            public Socket createSocket(HttpContext context)
                                    throws IOException {
                                Socket s = super.createSocket(context);
                                context.setAttribute("sock-address",
                                        s.getRemoteSocketAddress());
                                return s;
                            }
                        }).build(), new SystemDefaultDnsResolver());

        CloseableHttpClient minimal = HttpClients.createMinimal(m);

        HttpGet get = new HttpGet(s);

        HttpClientContext context = HttpClientContext.create();

        CloseableHttpResponse response = minimal.execute(get, context);

        InetSocketAddress addr = (InetSocketAddress) context
                .getAttribute("sock-address");

        HttpHost target = (HttpHost) context
                .getAttribute(ExecutionContext.HTTP_TARGET_HOST);

        System.out.println(addr);
        System.out.println(target.getAddress());

    }

以及唯一的 Maven 依赖项：

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.3.3</version>
</dependency>       

Answer 1

由于Socket s = super.createSocket(context); 在抽象中创建简单的 java Socket，我尝试覆盖 connectSocket 方法，这次它有效。这是工作示例：

  public static void main(String[] args) throws ClientProtocolException,
            IOException {

        String s = "http://google.com";

        PoolingHttpClientConnectionManager m = new PoolingHttpClientConnectionManager(
                RegistryBuilder.<ConnectionSocketFactory> create()
                        .register("http", new PlainConnectionSocketFactory() {

                            @Override
                            public Socket connectSocket(int connectTimeout,
                                    Socket socket, HttpHost host,
                                    InetSocketAddress remoteAddress,
                                    InetSocketAddress localAddress,
                                    HttpContext context) throws IOException {
                                context.setAttribute("sock-address",
                                        remoteAddress);
                                return super.connectSocket(connectTimeout,
                                        socket, host, remoteAddress,
                                        localAddress, context);
                            }
                        }).build(), new SystemDefaultDnsResolver());

        CloseableHttpClient minimal = HttpClients.custom()
                .setConnectionManager(m).build();

        HttpGet get = new HttpGet(s);

        HttpClientContext context = HttpClientContext.create();

        CloseableHttpResponse response = minimal.execute(get, context);

        InetSocketAddress addr = (InetSocketAddress) context
                .getAttribute("sock-address");

        System.out.println(addr.getAddress().getHostAddress());

    }

此外，一个站点可以有多个可以解析的 IP，上层解决方案将只选择它连接的第一个。如果您想要其他 IP，您必须自己解决它们：

SystemDefaultDnsResolver r = new SystemDefaultDnsResolver();
InetAddress[] resolve = r.resolve("google.com");

这可能会导致额外的 dns 检查和糟糕的性能。我读到的是设置nscd服务来缓存 dns 检查并加速请求。