返回 2xx 以外的代码时，如何使用 HttpURLConnection 获取响应正文?

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问题描述

我在检索 Json 响应时遇到问题，以防服务器返回错误.请参阅下面的详细信息.

I have problem with retrieving Json response in case when server returns error. See details below.

我使用 java.net.HttpURLConnection.我设置请求属性，然后我做:

I use java.net.HttpURLConnection. I setup request properties, then I do:

conn = (HttpURLConnection) url.openConnection();

之后，当请求成功时，我得到响应 Json:

After that, when request is successful, I get response Json:

br = new BufferedReader(new InputStreamReader((conn.getInputStream())));
sb = new StringBuilder();
String output;
while ((output = br.readLine()) != null) {
  sb.append(output);
}
return sb.toString();

...问题是:

当服务器返回诸如 50x 或 40x 之类的错误时，我无法检索收到的 Json.以下行抛出 IOException:

... and the problem is:

I can't retrieve Json received when the server returns some error like 50x or 40x,. Following line throws IOException:

br = new BufferedReader(new InputStreamReader((conn.getInputStream())));
// throws java.io.IOException: Server returned HTTP response code: 401 for URL: www.example.com

服务器肯定会发送正文，我在外部工具 Burp Suite 中看到它:

The server sends body for sure, I see it in external tool Burp Suite:

HTTP/1.1 401 Unauthorized

{"type":"AuthApiException","message":"AuthApiException","errors":[{"field":"email","message":"Invalid username and/or password."}]}

我可以使用以下方法获取响应消息(即内部服务器错误")和代码(即500"):

I can get response message (i.e. "Internal Server Error") and code (i.e. "500") using following methods:

conn.getResponseMessage();
conn.getResponseCode();

但是我无法检索请求正文...也许图书馆中有一些我没有注意到的方法?

But I can't retrieve request body... maybe there is some method I didn't notice in the library?

推荐答案

错误的方法被用于错误，这里是工作代码:

Wrong method was used for errors, here is the working code:

BufferedReader br = null;
if (100 <= conn.getResponseCode() && conn.getResponseCode() <= 399) {
    br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
} else {
    br = new BufferedReader(new InputStreamReader(conn.getErrorStream()));
}

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