问Java调用API请求链接报错？

我的请求链接已经生成了，在浏览器的地址栏里输入可以得到返回结果，但是在Java代码里请求出现错误：

{"Response":{"Error":{"Code":"AuthFailure.SignatureFailure","Message":"The provided credentials could not be validated. Please check your signature is correct."},"RequestId":"230be362-1932-472c-90da-ee7c75b4502a"}}

附请求代码：

public String getTrans() throws Exception{

String url = getTransUrl();

URL realUrl = new URL(url);

HttpURLConnection conn = (HttpURLConnection) realUrl.openConnection();

conn.setRequestMethod("GET");

conn.setDoOutput(true);

conn.setDoInput(true);

conn.setUseCaches(false);

conn.connect();

BufferedReader in = new BufferedReader(new InputStreamReader(

conn.getInputStream()));

String result=in.readLine();

in.close();

return result;

}

上面的url字符串在浏览器输入可以得到返回结果