java httpclient发送请求

Java HttpClient是一个发送HTTP请求的开源库，可以用来发送GET、POST等请求。下面是使用HttpClient发送POST请求的示例代码：

import org.apache.http.HttpEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

public class HttpClientExample {
    public static void main(String[] args) {
        CloseableHttpClient httpClient = HttpClients.createDefault();
        try {
            HttpPost httpPost = new HttpPost("http://example.com/api/endpoint");
            httpPost.addHeader("Content-Type", "application/json");
            
            String jsonData = "{\"key1\":\"value1\", \"key2\":\"value2\"}";
            StringEntity entity = new StringEntity(jsonData);
            httpPost.setEntity(entity);
            
            CloseableHttpResponse response = httpClient.execute(httpPost);
            try {
                HttpEntity responseEntity = response.getEntity();
                String responseBody = EntityUtils.toString(responseEntity);
                System.out.println(responseBody);
            } finally {
                response.close();
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                httpClient.close();
            } catch (Exception e) {
                e.printStackTrace();            }
        }
    }
}

以上代码使用了Apache HttpClient库，它需要引入相关的jar包。首先创建一个CloseableHttpClient对象，然后创建一个HttpPost对象，并设置请求URL和请求头部信息。接着创建一个StringEntity对象，将请求参数转化为JSON格式，并将其设置为HttpPost的实体。最后执行HttpPost请求，获取响应实体，将其转化为字符串并打印出来。最后关闭HttpClient。