httpclientAPI调用

HttpClient是Java的一个HTTP通讯库，可以用于发送HTTP请求和接收HTTP响应。

在使用HttpClient之前，需要先下载相关的jar包，比如httpclient、httpcore等，然后在代码中引入相关的类库。

以下是使用HttpClient发送一个HTTP GET请求的示例代码：

import java.io.IOException;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
 
public class HttpClientDemo {
 
    public static void main(String[] args) {
        CloseableHttpClient httpclient = HttpClients.createDefault();
        try {
            HttpGet httpget = new HttpGet("http://www.baidu.com/");
 
            System.out.println("Executing request " + httpget.getRequestLine());
 
            HttpResponse response = httpclient.execute(httpget);
            HttpEntity entity = response.getEntity();
 
            System.out.println("----------------------------------------");
 
            if (entity != null) {
                System.out.println(EntityUtils.toString(entity));
            }
 
            EntityUtils.consume(entity);
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                httpclient.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

该代码创建了一个CloseableHttpClient实例，然后构造一个HttpGet请求。使用httpclient.execute()方法发送该请求，并接收响应。最后使用EntityUtils.toString()方法将响应内容转换为字符串输出。最后，关闭HttpClient实例。