有什么方法可以在Jsoup中使用连接池吗？

在Jsoup中，可以通过使用连接池来提高爬取网页的效率和性能。连接池可以重复使用已经建立好的网络连接，避免频繁地创建和关闭连接，从而减少资源消耗和网络延迟。

要在Jsoup中使用连接池，可以借助第三方库如Apache HttpClient来实现。下面是一种实现方式：

导入所需的依赖：

<dependencies>
    <dependency>
        <groupId>org.apache.httpcomponents</groupId>
        <artifactId>httpclient</artifactId>
        <version>4.5.13</version>
    </dependency>
</dependencies>

创建连接池管理器：

import org.apache.http.HttpHost;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.config.ConnectionConfig;
import org.apache.http.config.RegistryBuilder;
import org.apache.http.conn.ConnectionKeepAliveStrategy;
import org.apache.http.conn.DnsResolver;
import org.apache.http.conn.HttpConnectionFactory;
import org.apache.http.conn.ManagedHttpClientConnectionFactory;
import org.apache.http.conn.routing.HttpRoutePlanner;
import org.apache.http.conn.socket.ConnectionSocketFactory;
import org.apache.http.conn.socket.LayeredConnectionSocketFactory;
import org.apache.http.conn.ssl.NoopHostnameVerifier;
import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
import org.apache.http.conn.ssl.TrustSelfSignedStrategy;
import org.apache.http.impl.DefaultConnectionReuseStrategy;
import org.apache.http.impl.NoConnectionReuseStrategy;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.DefaultHttpRequestRetryHandler;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.impl.conn.DefaultHttpResponseParserFactory;
import org.apache.http.impl.conn.DefaultHttpResponseParserFactory;
import org.apache.http.impl.conn.ManagedHttpClientConnectionFactory;
import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
import org.apache.http.protocol.HttpContext;
import org.apache.http.ssl.SSLContextBuilder;

import javax.net.ssl.HostnameVerifier;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLException;
import javax.net.ssl.SSLSession;
import java.io.IOException;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.nio.charset.StandardCharsets;
import java.security.KeyManagementException;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import java.util.concurrent.TimeUnit;

public class JsoupConnectionPoolManager {

    private static final int DEFAULT_MAX_TOTAL_CONNECTIONS = 200; // 最大连接数
    private static final int DEFAULT_MAX_PER_ROUTE_CONNECTIONS = 20; // 每个路由的最大连接数
    private static final int DEFAULT_CONNECT_TIMEOUT = 5000; // 连接超时时间
    private static final int DEFAULT_READ_TIMEOUT = 10000; // 读取超时时间

    private PoolingHttpClientConnectionManager connectionManager;
    private CloseableHttpClient httpClient;

    public JsoupConnectionPoolManager() {
        ConnectionSocketFactory plainsf = PlainConnectionSocketFactory.getSocketFactory();
        LayeredConnectionSocketFactory sslsf = null;
        try {
            sslsf = new SSLConnectionSocketFactory(SSLContextBuilder.create().loadTrustMaterial(new TrustSelfSignedStrategy()).build(), NoopHostnameVerifier.INSTANCE);
        } catch (NoSuchAlgorithmException | KeyStoreException | KeyManagementException e) {
            e.printStackTrace();
        }

        Registry<ConnectionSocketFactory> registry = RegistryBuilder.<ConnectionSocketFactory>create()
                .register("http", plainsf)
                .register("https", sslsf)
                .build();

        connectionManager = new PoolingHttpClientConnectionManager(registry);
        connectionManager.setMaxTotal(DEFAULT_MAX_TOTAL_CONNECTIONS);
        connectionManager.setDefaultMaxPerRoute(DEFAULT_MAX_PER_ROUTE_CONNECTIONS);
        connectionManager.setValidateAfterInactivity(1000);

        ConnectionConfig connectionConfig = ConnectionConfig.custom()
                .setCharset(StandardCharsets.UTF_8)
                .build();
        connectionManager.setDefaultConnectionConfig(connectionConfig);

        RequestConfig defaultRequestConfig = RequestConfig.custom()
                .setConnectTimeout(DEFAULT_CONNECT_TIMEOUT)
                .setSocketTimeout(DEFAULT_READ_TIMEOUT)
                .setConnectionRequestTimeout(DEFAULT_CONNECT_TIMEOUT)
                .build();

        httpClient = HttpClients.custom()
                .setConnectionManager(connectionManager)
                .setConnectionManagerShared(true)
                .evictIdleConnections(60, TimeUnit.SECONDS)
                .evictExpiredConnections()
                .setConnectionTimeToLive(60, TimeUnit.SECONDS)
                .setDefaultRequestConfig(defaultRequestConfig)
                .setConnectionReuseStrategy(DefaultConnectionReuseStrategy.INSTANCE)
                .setKeepAliveStrategy(DefaultConnectionKeepAliveStrategy.INSTANCE)
                .setRetryHandler(new DefaultHttpRequestRetryHandler(3, true))
                .build();
    }

    public CloseableHttpClient getHttpClient() {
        return httpClient;
    }

}

使用连接池进行网络请求：

import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;

import java.io.IOException;

public class Main {

    public static void main(String[] args) {
        String url = "https://example.com";
        JsoupConnectionPoolManager connectionPoolManager = new JsoupConnectionPoolManager();
        try {
            Document doc = Jsoup.connect(url)
                    .userAgent("Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.54 Safari/537.36")
                    .timeout(5000)
                    .get();
            System.out.println(doc.title());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

以上代码示例中，通过JsoupConnectionPoolManager创建了一个连接池管理器，并通过getHttpClient()方法获取了一个可重用的HttpClient实例。然后可以使用Jsoup.connect(url)来构建Jsoup连接，并在连接上设置一些参数（如User-Agent、超时时间等）。最后调用.get()方法来获取网页内容。

使用连接池可以提高爬取网页的效率和性能，同时也能避免对目标网站产生过大的访问压力。在使用连接池时，需要注意合理配置连接池的最大连接数和每个路由的最大连接数，以及适当设置超时时间等参数，根据实际情况调整。