如果服务器返回502错误，如何读取HTTP响应？

Question

我使用URLConnection向服务器发送POST请求，我使用以下代码来读取响应：

String line;
BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));   
while ((line = reader.readLine()) != null) {
    response += line;
}
reader.close();

但是，服务器有时会在响应中返回502错误并显示有意义的错误消息，我想获取该消息。我的问题是，在这种情况下尝试创建BufferedReader会产生java.io.IOException：

Server returned HTTP response code: 502 for URL: <url>

如何绕过这个？

Answer 1

沿着这些行修改代码，以便您可以获取errorstream而不是抛出IOException

HttpURLConnection httpConn = (HttpURLConnection)connection;
InputStream is;
if (httpConn.getResponseCode() >= 400) {
    is = httpConn.getErrorStream();
} else {
    is = httpConn.getInputStream();
}

BufferedReader reader = new BufferedReader(new  InputStreamReader(is));   
while ((line = reader.readLine()) != null) {
     response += line;
}
reader.close();