java httpclient 连接池 代码

很好，我明白你的要求了。以下是一个简单的Java HTTPClient连接池代码示例：

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.methods.HttpRequestBase;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
import org.apache.http.util.EntityUtils;

import java.io.IOException;

public class HttpUtils {

    private static final int MAX_TOTAL_CONNECTIONS = 200;
    private static final int MAX_ROUTE_CONNECTIONS = 20;
    private static final int TIMEOUT = 3000;

    private static CloseableHttpClient httpClient;

    static {
        PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
        cm.setMaxTotal(MAX_TOTAL_CONNECTIONS);
        cm.setDefaultMaxPerRoute(MAX_ROUTE_CONNECTIONS);

        RequestConfig requestConfig = RequestConfig.custom()
                .setSocketTimeout(TIMEOUT)
                .setConnectTimeout(TIMEOUT)
                .setConnectionRequestTimeout(TIMEOUT)
                .build();

        httpClient = HttpClientBuilder.create()
                .setDefaultRequestConfig(requestConfig)
                .setConnectionManager(cm)
                .build();
    }

    public static String doGet(String url) throws IOException {
        HttpGet httpGet = new HttpGet(url);
        return execute(httpClient, httpGet);
    }

    public static String doPost(String url, String body, ContentType contentType) throws IOException {
        HttpPost httpPost = new HttpPost(url);
        httpPost.setEntity(new StringEntity(body, contentType));
        return execute(httpClient, httpPost);
    }

    private static String execute(CloseableHttpClient client, HttpRequestBase request) throws IOException {
        HttpResponse response = client.execute(request);
        HttpEntity entity = response.getEntity();
        String result = EntityUtils.toString(entity);
        EntityUtils.consume(entity);
        return result;
    }
}

这里使用了Apache HttpComponents实现的Http客户端，并使用连接池技术来维护连接，以提高性能和可靠性。其中，最大连接数设置为200，每个路由最大连接数设置为20，超时时间设置为3秒。提供了简单的GET和POST请求方法，并支持指定内容类型。