本文介紹了使用HttpURLConnection執行cURL命令的Java返回204(HTTP_NO_CONTENT)的處理方法，對大家解決問題具有一定的參考價值，需要的朋友們下面隨著小編來一起學習吧！
問題描述
我使用的是Java 11。在命令行上執行時，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'
返回以下內容：
{errorMessage: 'PaperTrail API only available in enterprise edition'}
但是，當我嘗試使用HttpURLConnection在Java應用程序中執行相同的URL時，它返回空白響應。
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;
}
以空白響應輸出以下內容：
204 Response: ''.
問題
如何使Java應用程序也返回與命令行調用相同的結果？
更新
我有一個不同的POST URL，我也需要調用它，我可以成功地調用它。所以我的Get調用有問題。
private static final String USER_AGENT = "Mozilla/5.0";
例如，Get調用返回204，沒有內容。
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;
}
返回200的POST調用和預期內容。
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調用起作用了，我想我一定是GET調用出了什么問題。
推薦答案
您是否嘗試在您的Java代碼中設置cURL將使用的相同用戶代理？類似curl/7.37.0的內容？
就我所知，這應該就是所有的不同之處。在重定向之后，撇開卷曲。但由于沒有重定向，我猜可能是用戶代理起了作用。
有很多服務器應用程序在被瀏覽器調用時表現不同(就像您通過將User-Agent設置為Mozilla/5.0來使其思考一樣)，而不是像cURL這樣的其他應用程序。
這篇關于使用HttpURLConnection執行cURL命令的Java返回204(HTTP_NO_CONTENT)的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，
