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

Question

我使用的是 Java 11。当我在命令行上执行时，我有以下 curl 命令：

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'

返回以下内容：

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

但是，当我尝试使用 HttpURLConnection 在 Java 应用程序中执行相同的 URL 时，它返回一个空白响应。

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;
}

以空白响应输出以下内容：

204 Response: ''.

问题

如何让 Java 应用程序也返回与命令行调用相同的内容？

更新

我有一个不同的 POST url，我也需要调用它，我可以成功调用它。所以我的 GET 调用有问题。

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

例如GET 调用返回 204，没有内容。

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;
}

POST 调用，返回 200 和预期的内容。

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;
}

所以看到 POST 调用有效，我想我一定是对 GET 调用做错了。

Answer 1

根据您的描述，原始调用产生了错误。

假设您在 GET 的 java 代码中也遇到了某种形式的错误，您将捕获异常并简单地记录它。然后你会返回null而不是一个字符串，这会导致你的响应没有内容，即204。

Answer 2

您是否尝试过在您的 Java 代码中设置与 cURL 相同的用户代理？类似curl/7.37.0？ 据我所知，这应该是全部，有什么不同。除了重定向后的 cURL。但由于没有重定向，我想可能是用户代理有所作为。

有很多服务器应用程序在被浏览器调用时表现不同（就像您通过将 User-Agent 设置为 Mozilla/5.0 来想象的那样），而不是其他一些应用程序，例如 cURL。