当 java 中的请求失败时，如何获取 http 响应正文？

Question

I'm looking for a way to receive the response body when a request ends up with the status 400. I'm now using java.net to make http connection.

Here is the code I'm using:

InputStream response = new URL("http://localhost:8888/login?token=token").openStream();
try (Scanner scanner = new Scanner(response)) {
    String responseBody = scanner.useDelimiter("\\A").next();
    System.out.println(responseBody);
}

Right now, I end up with this error

java.io.IOException: Server returned HTTP response code: 400 for URL

When I open the url in my browser it shows me a json file representing what went wrong, but now, I can't receive that response in java.

Answer 1

Try the below code:

package com.abc.test;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class Test {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        try {
            String url = "http://localhost:8888/login?token=token";
            HttpURLConnection connection = (HttpURLConnection) new URL(url).openConnection();
            int responseCode = connection.getResponseCode();
            InputStream inputStream;
            if (200 <= responseCode && responseCode <= 299) {
                inputStream = connection.getInputStream();
            } else {
                inputStream = connection.getErrorStream();
            }

            BufferedReader in = new BufferedReader(new InputStreamReader(inputStream));

            StringBuilder response = new StringBuilder();
            String currentLine;

            while ((currentLine = in.readLine()) != null) 
                response.append(currentLine);

            System.out.println(response.toString());
            in.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }       
    }

}

Answer 2

I changed my approach and now it works.

URL obj = new URL("http://localhost:8888/login?token=token");
HttpURLConnection con = (HttpURLConnection) obj.openConnection();
con.setRequestMethod("GET");
con.setRequestProperty("User-Agent", USER_AGENT);
int responseCode = con.getResponseCode();
System.out.println("GET Response Code :: " + responseCode);

System.out.println("Status Code : " + con.getResponseMessage());
BufferedReader in = new BufferedReader(new InputStreamReader(
con.getErrorStream()));
String inputLine;
StringBuilder response = new StringBuilder();
while ((inputLine = in.readLine()) != null) {
    response.append(inputLine);
}
in.close();
System.out.println("Response Body:");
System.out.println(response.toString());