Java http请求json数据

public static String sendJson(String url, String json) {
    String returnValue = "调用接口失败";
    CloseableHttpClient httpClient = HttpClients.createDefault();
    ResponseHandler<String> responseHandler = new BasicResponseHandler();
    try{
        //第一步：创建HttpClient对象
        httpClient = HttpClients.createDefault();

        //第二步：创建httpPost对象
        HttpPost httpPost = new HttpPost(url);

        //第三步：给httpPost设置JSON格式的参数
        StringEntity requestEntity = new StringEntity(json,"utf-8");
        requestEntity.setContentEncoding("UTF-8");
        httpPost.setHeader("Content-type", "application/json");
        httpPost.setEntity(requestEntity);

        //第四步：发送HttpPost请求，获取返回值
        returnValue = httpClient.execute(httpPost,responseHandler); //调接口获取返回值时，必须用此方法

    }
    catch(Exception e){
        e.printStackTrace();
    }finally {
        try {
            httpClient.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    //第五步：处理返回值
    return returnValue;
}