Java 使用 HttpURLConnection 执行 curl 命令返回 204 (HTTP_NO_CONTENT)

Question

I am using Java 11. I have the the following curl command, when I execute on the command line:

curl --location --request GET 'http://xxx.xxx.co.za:8080/document/details/Select+docId+From+%27Workflow+Club%2FCustomer+Invoices%27+where+recursive+%3D+true+and+invoice_number+%3D%271221669023%27' --header 'Authorization: Basic xxx'

Returns the following:

{errorMessage: 'PaperTrail API only available in enterprise edition'}

However, when I try execute the same URL in a Java application using HttpURLConnection , it returns a blank response.

private static final String USER_AGENT = "Mozilla/5.0";

private static final String GET_URL = "http://xxx.xxx.co.za:8080/document/details/";
private static final String GET_URL_QRY = "Select docId From 'Workflow Club/Customer Invoices' where recursive = true and invoice_number =':1'";
private static final String GET_AUTH_ENC = "Basic xxx";

@Override
public String getDocId(Long invoiceNumber) {
    String get_url_qry = StringUtils.replace(GET_URL_QRY, ":1", Long.toString(invoiceNumber));
    get_url_qry = URLEncoder.encode(get_url_qry, StandardCharsets.UTF_8);
    final String get_url = GET_URL+get_url_qry;
    try {
        URL url = new URL(get_url);
        HttpURLConnection con = (HttpURLConnection) url.openConnection();
        con.setRequestProperty("Authorization", GET_AUTH_ENC);
        con.setRequestMethod("GET");
        con.setRequestProperty("User-Agent", USER_AGENT);
        int responseCode = con.getResponseCode();
        logger.info(get_url+" -> GET Response Code :: " + responseCode);
        if (responseCode == HttpURLConnection.HTTP_OK || responseCode == HttpURLConnection.HTTP_NO_CONTENT) { // success
            BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
            String inputLine;
            StringBuffer response = new StringBuffer();
            while ((inputLine = in.readLine()) != null) {
                response.append(inputLine);
            }
            in.close();
            String resp = response.toString();
            logger.info(responseCode+" Response: '"+resp+"'.");
        } else {
            logger.error("GET request did not work (responseCode: "+responseCode+").");
        }
    } catch (MalformedURLException e) {
        logger.error("MalformedURLException creating URL '"+get_url+"'. "+e.getMessage());
    } catch (IOException e) {
        logger.error("IOException creating connection from URL '"+get_url+"'. "+e.getMessage());
    }
    return null;
}

Outputs the following with a blank response:

204 Response: ''.

Question

How do I get the Java application to also return the same as the command line call?

UPDATE

I have a different POST url, that I need to call too, and I can call it successfully. So there's something wrong with my GET call.

private static final String USER_AGENT = "Mozilla/5.0";

Eg GET call that returns a 204, with no content.

private String getDocId(Long invoiceNumber) {
    String get_url_qry = StringUtils.replace(GET_URL_QRY, ":1", Long.toString(invoiceNumber));
    get_url_qry = URLEncoder.encode(get_url_qry, StandardCharsets.UTF_8);
    final String get_url = GET_URL+get_url_qry;
    try {
        URL url = new URL(get_url);
        HttpURLConnection con = (HttpURLConnection) url.openConnection();
        con.setRequestProperty("Authorization", GET_AUTH_ENC);
        con.setRequestMethod("GET");
        con.setRequestProperty("User-Agent", USER_AGENT);
        con.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
        Map<String,String> data = handleResponse(con);
        return data.get("docId");
    } catch (MalformedURLException e) {
        logger.error("MalformedURLException creating URL '"+get_url+"'. "+e.getMessage());
    } catch (IOException e) {
        logger.error("IOException creating connection from URL '"+get_url+"'. "+e.getMessage());
    }
    return null;
}

The POST call, that returns a 200, and the expected content.

private String getDocLink(String docId) {
    if (StringUtils.isNotBlank(docId)) {
        try {
            URL url = new URL(POST_URL);
            HttpURLConnection con = (HttpURLConnection) url.openConnection();
            con.setRequestProperty("Authorization", GET_AUTH_ENC);
            con.setRequestMethod("POST");
            con.setRequestProperty("User-Agent", USER_AGENT);
            con.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
            byte[] postDataBytes = getPostData(docId);
            con.setRequestProperty("Content-Length", String.valueOf(postDataBytes.length));
            con.setDoOutput(true);
            con.getOutputStream().write(postDataBytes);
            Map<String,String> data = handleResponse(con);
            return data.get("url");
        } catch (IOException e) {
            logger.error("IOException creating connection from URL '"+POST_URL+"'. "+e.getMessage());
        }
    } else {
        logger.error("No docId provided when trying to get a document link.");
    }
    return null;
}

So seeing the that POST call works, I think I must be doing something wrong with the GET call.

Answer 1

Did you try, setting the same user agent in your Java Code, cURL would use? something like curl/7.37.0 ? As far as I can tell, that should be all, what differs. Aside cURL following redirects. But as there is no redirect, I guess it might be the User Agent making a difference.

There are a lot of server applications, behaving differently, when they are called by a browser (Like you make it think by setting the User-Agent to Mozilla/5.0 ), instead of some other application, like cURL.

Answer 2

From what you describe, the original call produces an error.

Assuming that you are also getting some form of error in the java code of your GET, you will catch the exception and simply log it. Then you will return null instead of a string, which will cause your response to have no content, ie 204.