Java 带有 JSON 的 Http 415 不支持的媒体类型错误

我用一个JSON请求调用一个REST服务，它的响应是一个HTTP 415 "Unsupported Media Type"错误.

请求内容类型设置为("Content-Type", "application/json; charset=utf8").

如果我不在请求中包含JSON对象，它可以很好地工作.我正在使用JSON的google-gson-2.2.4库.

我试着使用了几个不同的库，但没有什么不同.

谁能帮我解决这个问题吗？

以下是我的代码:

public static void main(String[] args) throws Exception
{

    JsonObject requestJson = new JsonObject();
    String url = "xxx";

    //method call for generating json

    requestJson = generateJSON();
    URL myurl = new URL(url);
    HttpURLConnection con = (HttpURLConnection)myurl.openConnection();
    con.setDoOutput(true);
    con.setDoInput(true);

    con.setRequestProperty("Content-Type", "application/json; charset=utf8");
    con.setRequestProperty("Accept", "application/json");
    con.setRequestProperty("Method", "POST");
    OutputStream os = con.getOutputStream();
    os.write(requestJson.toString().getBytes("UTF-8"));
    os.close();


    StringBuilder sb = new StringBuilder();  
    int HttpResult =con.getResponseCode();
    if(HttpResult ==HttpURLConnection.HTTP_OK){
    BufferedReader br = new BufferedReader(new   InputStreamReader(con.getInputStream(),"utf-8"));  

        String line = null;
        while ((line = br.readLine()) != null) {  
        sb.append(line + "\n");  
        }
         br.close(); 
         System.out.println(""+sb.toString());  

    }else{
        System.out.println(con.getResponseCode());
        System.out.println(con.getResponseMessage());  
    }  

}
public static JsonObject generateJSON () throws MalformedURLException

{
   String s = "http://www.example.com";
        s.replaceAll("/", "\\/");
    JsonObject reqparam=new JsonObject();
    reqparam.addProperty("type", "arl");
    reqparam.addProperty("action", "remove");
    reqparam.addProperty("domain", "staging");
    reqparam.addProperty("objects", s);
    return reqparam;

}
}

requestJson.toString()的值为:

{"type":"arl","action":"remove","domain":"staging","objects":"http://www.example.com"}