springboot发送post请求带json参数如何写

在Spring Boot中发送POST请求并携带JSON参数，通常需要使用`RestTemplate`、`Feign`、`Retrofit`或者`HttpClient`等库。以下是使用`RestTemplate`的一个简单示例：

import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.web.client.RestTemplate;

public class ExampleService {

    private RestTemplate restTemplate = new RestTemplate();

    public void sendPostRequest(String url, Object requestBody) {
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_JSON);
        
        // 将对象转换为JSON字符串
        String json = new ObjectMapper()..writeValueAsString(requestBody);

        // 发送POST请求
        ResponseEntity<String> response = restTemplate.postForEntity(url, json, String.class);
        System.out.println("Response Status: " + response.getStatusCode());
        System.out.println("Response Body: " + response.getBody());
    }
}

在这个例子中，`requestBody`是你想要发送的JSON对象，`ObjectMapper`来自Jackson库，用于序列化Java对象为JSON。

如果你想使用HTTP客户端直接操作，可以使用`httpclient4.x`库：

import org.apache.http.entity.ContentType;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

CloseableHttpClient httpClient = HttpClients.createDefault();
HttpPost httpPost = new HttpPost("http://example.com/api");
httpPost.setHeader(HttpHeaders.CONTENT_TYPE, ContentType.APPLICATION_JSON_VALUE);
StringEntity requestJson = new StringEntity(json, ContentType.APPLICATION_JSON);
httpPost.setEntity(requestJson);

CloseableHttpResponse response = httpClient.execute(httpPost);
try {
    System.out.println("Response Status: " + response.getStatusLine());
    System.out.println("Response Body: " + EntityUtils.toString(response.getEntity()));
} finally {
    response.close();
    httpClient.close();
}