如何通过 java 代码在响应不是 200 的调用后捕获错误响应正文和错​​误代码？

Question

我正在编写下面的代码，但这只是在响应代码为 200 时捕获响应正文。对于所有其他情况，它都失败了。

图片 - postman post call and response where response code is not equal to 200

例如，当响应代码为 409 时，代码会抛出错误

线程“main”java.io.IOException 中的异常：服务器返回 HTTP 响应代码：409 用于 URL：http://fetch.product/v1/products/PD16798270/validate 在 java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1919) 在 java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1515) 在 com.Main.main(Main.java:58)

我在下面使用的代码 -

public static void main(String[] args) throws Exception {       
     
     String url = "http://fetch.product/v1/products/PD16798270/validate";    
     URL u = new URL(url);
    
     StringBuilder postData = new StringBuilder();
     byte[] postDataBytes = postData.toString().getBytes("UTF-8");
     
     HttpURLConnection conn = (HttpURLConnection)u.openConnection();
     conn.setRequestMethod("POST");      
     
     conn.setDoOutput(true);
     conn.getOutputStream().write(postDataBytes);
     
     Reader in = new BufferedReader(new InputStreamReader(conn.getInputStream(), "UTF-8"));
     StringBuilder sb = new StringBuilder();
     for (int c; (c = in.read()) >= 0;)
            sb.append((char)c);
     String response = sb.toString();
     System.out.println(response);
     
}

Answer 1

如果请求返回错误响应，您可以从连接的“错误流”中读取它。例如，无论请求返回成功还是错误，这都会读取正文：

InputStream input;
if (conn.getResponseCode() >= 400) {
    input = conn.getErrorStream();
} else {
    input = conn.getInputStream();
}

Reader in = new BufferedReader(new InputStreamReader(input, "UTF-8"));