java 调用http post请求传json过去

在Java中，通常会使用`HttpURLConnection`、`HttpClient`或第三方库如`Apache HttpClient`、`OkHttp`来进行HTTP POST请求并传递JSON数据。这里以常用的`HttpURLConnection`为例，展示如何发送POST请求并将JSON作为请求体：

import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import org.json.JSONObject;

public JSONObject sendPostJsonRequest(String url, JSONObject json) throws Exception {
    URL obj = new URL(url);
    HttpURLConnection con = (HttpURLConnection) obj.openConnection();
    
    // 设置请求方法为POST
    con.setRequestMethod("POST");
    con.setRequestProperty("Content-Type", "application/json; charset=UTF-8");

    // 将JSON转换为字节数组，并写入连接的输入流
    OutputStream os = con.getOutputStream();
    byte[] data = json.toString().getBytes("UTF-8");
    os.write(data);
    os.flush();
    os.close();

    // 获取响应状态码
    int responseCode = con.getResponseCode();
    if (responseCode == HttpURLConnection.HTTP_OK) {
        String response = readResponse(con.getInputStream());
        return new JSONObject(response); // 如果需要返回JSON对象，解析响应内容
    } else {
        throw new RuntimeException("Failed : HTTP error code : " + responseCode);
    }
}

private String readResponse(InputStream in) throws Exception {
    BufferedReader br = new BufferedReader(new InputStreamReader(in));
    StringBuilder response = new StringBuilder();
    String line;
    while ((line = br.readLine()) != null) {
        response.append(line);
    }
    br.close();
    return response.toString();
}