java中post推送json格式字符串

最近项目中遇到post推送json格式字符串，之前写过推送json数据，调用失败，才发现是直接推送字符串，只不过字符串是json的格式。

在postman中调用如下：

Java中代码如下：

 /**
     * 发送POST方法的请求
     * @param url 发送请求的 URL
     * @param jsonData 请求参数是Json格式字符串
     * @return 响应结果
     */
    public static String sendPostJsonStr(String url, String jsonData) {
        PrintWriter out = null;
        BufferedReader in = null;
        String result = "";
        try {
            HttpClient client = new HttpClient();
            PostMethod postMethod = new PostMethod(url);
            postMethod.addRequestHeader("Content-type", "application/json; charset=utf-8");
            byte[] requestBytes = jsonData.getBytes("utf-8"); // 将参数转为二进制流
            InputStream inputStream = new ByteArrayInputStream(requestBytes, 0, requestBytes.length);
            // 请求体
            RequestEntity requestEntity = new InputStreamRequestEntity(inputStream, requestBytes.length, "application/json; charset=utf-8");
            postMethod.setRequestEntity(requestEntity); // 将参数放入请求体
            client.executeMethod(postMethod);
            inputStream = postMethod.getResponseBodyAsStream();
            BufferedReader br = new BufferedReader(new InputStreamReader(inputStream));
            StringBuffer stringBuffer = new StringBuffer();
            String str= "";
            while((str = br.readLine()) != null){
                stringBuffer.append(str);
            }
            result=stringBuffer.toString();
        } catch (Exception e) {
            e.printStackTrace();
        }
        finally {
            try {
                if (out != null) {
                    out.close();
                }
                if (in != null) {
                    in.close();
                }
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
        return result;
    }

　　引用的jar包：commons-httpclient-3.1.jar、commons-logging-1.2.jar、commons-codec-1.9.jar