JAVA代码中访问外部接口传递JSON格式参数

/**
  * 访问指定的URL地址
  * urlStr url地址
  * json json格式字符串
  */
public static String getURLByPost(String urlStr, String json) {

        StringBuilder sb = new StringBuilder();
        String url = urlStr;
        // 创建连接对象
        HttpClient httpClient = new HttpClient();
        // 创建请求
        PostMethod method = new PostMethod(url);
        // 设置请求头格式为json格式
        RequestEntity entity = null;
        try {
            entity = new StringRequestEntity(json, "application/json", "UTF-8");
            // 设置请求体信息
            if (entity == null)
                return "";
            method.setRequestEntity(entity);
            // 设置请求头信息
            method.setRequestHeader("APPKEY", "C6C6E17AC153ED8DF8D61207");
            // 创建连接
            httpClient.executeMethod(method);
            // 获取返回信息
            InputStream in = method.getResponseBodyAsStream();
            InputStreamReader isr = new InputStreamReader(in, "UTF-8");
            char[] b = new char[4096];

            for (int n; (n = isr.read(b)) != -1;) {
                sb.append(new String(b, 0, n));
            }
        } catch (UnsupportedEncodingException e) {
            System.out.println("=====JSON数据转换有误。参数json数据：" + json + "END=====");
            e.printStackTrace();
        } catch (HttpException e) {
            System.out.println("=====URL连接失败。url：" + url + "END=====");
            e.printStackTrace();
        } catch (IOException e) {
            System.out.println("=====参数传递失败。END=====");
            e.printStackTrace();
        }
        return sb.toString();
    }