java httpclient发送post请求

以下是使用Apache 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;

import java.io.IOException;

public class HttpClientExample {

    public static void main(String[] args) {

        // 创建HttpClient实例
        CloseableHttpClient httpClient = HttpClients.createDefault();

        // 创建HttpPost请求实例
        HttpPost httpPost = new HttpPost("http://example.com/api");

        // 设置请求头信息
        httpPost.setHeader("Content-Type", "application/json");

        // 设置请求体信息
        String requestBody = "{\"name\": \"John\", \"age\": 30}";
        StringEntity requestEntity = new StringEntity(requestBody, "UTF-8");
        httpPost.setEntity(requestEntity);

        // 发送POST请求并获取响应
        CloseableHttpResponse response = null;
        try {
            response = httpClient.execute(httpPost);

            // 获取响应实体
            HttpEntity responseEntity = response.getEntity();

            // 打印响应状态码
            System.out.println(response.getStatusLine().getStatusCode());

            // 打印响应内容
            System.out.println(EntityUtils.toString(responseEntity));

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (response != null) {
                    response.close();
                }
                httpClient.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

    }
}

注意：在使用HttpClient发送POST请求时，需要设置请求头信息和请求体信息。请求头信息可以根据实际情况设置，请求体信息一般为JSON格式的字符串。需要注意的是，请求体字符串需要使用StringEntity类进行包装。在发送POST请求后，需要关闭响应和HttpClient实例。