Having some troubles communicating with a Express REST api through Java.
A simple route which is online at: http://localhost:5555/test
router.post('/test', function (req, res, next) {
console.log("recived request");
res.sendStatus(200);
});
As you can see, this route doesn't do much tho, only for connection testing purpose.
Spending like hours searching but didn't find a good example yet.
Still got this peace of code but got exception.
URL url = new URL("http://localhost:5555/test");
HttpURLConnection connection = (HttpURLConnection)url.openConnection();
connection.setRequestMethod("POST");
connection.setDoOutput(true);
OutputStreamWriter writer = new OutputStreamWriter(connection.getOutputStream());
writer.write("test");
If someone knows a peace of code I could work, that would be great!
Thanks
Edit
Server is running:
> node index.js
server running on port: 5555
connection open
Exception from Java:
System.err: null
Your Express route is expecting a POST and your code does a GET request (openConnection). Try to change it to get an retry your operation.
Because your route accepts POST method, you may have 2 options.
Change your request method in Java code to POST
connection.setRequestMethod("POST");
Change your route accepts GET
Related
i'm running a simple java program to get HttpResponse codes, however for some reason not all codes happen to be 200. I find this odd because when checking the network tab for certain URLs like www.reddit.com, the Response is 200, but my program is returning a different value.
The code below...
try{
String urlName = "http://www.reddit.com";
URL url = new URL(urlName);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
connection.connect();
String message = connection.getResponseMessage();
System.out.println("Message: " + message);
int code = connection.getResponseCode();
System.out.println(Integer.toString(code));
}
catch(Exception e){
e.printStackTrace();
}
Lastly, is there a reason to set the RequestMethod to GET and connection again? I get the response code whether or not I have that code because the connection executes openConnection();
Goal - make all valid connections return 200
You said that you're seeing a 301 for Reddit and a 302 for Facebook. Those status codes mean that you're getting redirected. Your browser's following them; your code isn't.
Java's built-in HTTP support is not great for end-users. I strongly recommend using a better HTTP client library, such as Apache's HttpClient, or Horizon, which is built on top of Apache (for synchronous requests) and Ning (for async).
Full disclosure: I work for HubSpot; Horizon is one of our open-source libraries.
It would be nice if you posted the error code it did give...
I ran your code myself and the error was 301, meaning moved permanently.
If you go to http://www.reddit.com yourself, you will see that you get redirected to the httpS version of reddit. Changing this in the urlName will fix your problem.
Edit: same goes for facebook as i saw in comments to your question, google does not require https always so that does work.
I have the following code:
HttpURLConnection conn = null;
BufferedReader in = null;
StringBuilder sb = null;
InputStream is = null;
conn = (HttpURLConnection) url.openConnection();
// Break-point A
conn.setDoInput(true);
conn.setDoOutput(true);
conn.setRequestMethod("POST");
// Break-point B
conn.setRequestProperty("X-TP-APP", Constants.X_TP_APP);
conn.setRequestProperty("X-TP-DEVICE", Constants.X_TP_DEVICE);
conn.setRequestProperty("X-TP-LOCALE", Constants.X_TP_LOCALE);
conn.setRequestProperty("Content-Type", contentType);
conn.setRequestProperty("Accept", accept);
conn.setRequestProperty("Authorization", SystemApi.TOKEN_STR);
conn.setUseCaches(false);
conn.setConnectTimeout(30000);
conn.getOutputStream().write(req.getBytes("UTF-8"));
conn.getOutputStream().flush();
conn.getOutputStream().close();
is = conn.getInputStream();
in = new BufferedReader(new InputStreamReader(is));
int statusCode = conn.getResponseCode();
// Break-point C
The code is running fine without problem (when breakpoint(A,B) is disabled)
I tried to find out when does HttpURLConnection really call the request and place breakpoint(A) after conn = getConnection(strURL);
and continue the code, but then at the end, at breakpoint(C), server would return me 401 - Unauthorized, which mean my Authorization header is not in the request.
It seem like that we are trying to open a connection first, and then set the header as fast as we can. If we are not fast enough, then the request is called anyway, which doesn't seem right.
My question and concern:
When does HttpURLConnection really call the request?
Is this what is actually happening? Is this the correct way to do so?
Is there a better way to make sure the header is set before calling the request?
Per the docs, the actual connection is made when the connect() method is invoked on the [Http]UrlConnection. That may be done manually, or it may be done implicitly by certain other methods. The Javadocs for UrlConnection.connect() say, in part:
URLConnection objects go through two phases: first they are created, then they are connected. After being created, and before being connected, various options can be specified (e.g., doInput and UseCaches). After connecting, it is an error to try to set them. Operations that depend on being connected, like getContentLength, will implicitly perform the connection, if necessary.
Note in particular the last sentence. I don't see anything in your code that would require the connection to be established until the first conn.getOutputStream(), and I read the docs as saying that the connection object will not enter the "connected" state until some method is invoked on it that requires that. Until such a time, it is ok to set connection properties.
Moreover, the docs definitely state that methods that set properties on the connection (and setRequestProperty() in particular) will throw an IllegalStateException if invoked when the connection object is already connected.
It is possible that your Java library is buggy in the manner you describe, but that would certainly be in conflict with the API specification. I think it's more likely that the explanation for the behavior you observe is different, and I recommend you capture and analyze the actual HTTP traffic to determine what's really going on.
Actually what really happened is, in the debug mode, I used conn.getResponseCode() in the expressions, which force the conn.getResponseCode() to run.
When it is not connected yet, getResponseCode() would calls connect() before the request is prepared.
Hence it would return me 401.
Since Android using the same HttpURLConnection, I did some capture the packet exchange to see what is happening under the hood.
I detailed my experiment in this post Can you explain the HttpURLConnection connection process?
To outline the network activity for your program.
At Breakpoint A No physical connection is made to the remote server. You get a logical handle to a local connection object.
At Breakpoint B You just configure the local connection object, nothing more.
conn.getOutputStream() Network connection starts here, but no payload is transferred to the server.
conn.getInputStream() Payload (http headers, content) are sent to the server, and you get the response (buffered into input stream, and also the response code etc.)
To Answer your question
When does HttpURLConnection really call the request?
getInputStream() triggers network layer to send out application payload and got responses.
Is this what is actually happening? Is this the correct way to do so?
No. openConnection() does not initiate network activity. You are getting back a local handle for future connection, not an active connection.
Is there a better way to make sure the header is set before calling the request?
You don't need to make sure header is set. The header payload isn't sent to the server until you ask for response (such as getting the response code, or opening a inputStream )
I wrote some simple code in Java, the method should connect to the website and return the BufferedReader.
private BufferedReader getConnection(String url_a) {
URL url;
try {
System.out.println("getting connection");
url = new URL(url_a);
HttpURLConnection urlConnection = (HttpURLConnection)
url.openConnection();
urlConnection.addRequestProperty("User-Agent",
"Mozilla/5.0 (X11; U; Linux i586; en-US; rv:1.7.3) Gecko/20040924"
+ "Epiphany/1.4.4 (Ubuntu)");
inStream = new InputStreamReader(urlConnection.getInputStream());
return new BufferedReader(inStream);
} catch (Exception ex) {
Logger.getLogger(Reader.class.getName()).log(Level.SEVERE, null, ex);
}
return null;
}
When I use it on my PC, it works fine but when I put .jar file on the server I get this error:
java.net.SocketException: Unexpected end of file from server
at sun.net.www.http.HttpClient.parseHTTPHeader(HttpClient.java:718)
at sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:579)
at sun.net.www.http.HttpClient.parseHTTPHeader(HttpClient.java:715)
at sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:579)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1322)
at dataconverter.Reader.getConnection(Reader.java.260)
Problem is quite strange because the exception isn't thrown each time, sometimes everything is OK and program works fine.
Has anybody got any ideas?
"Unexpected end of file" implies that the remote server accepted and closed the connection without sending a response. It's possible that the remote system is too busy to handle the request, or that there's a network bug that randomly drops connections.
It's also possible there is a bug in the server: something in the request causes an internal error, and the server simply closes the connection instead of sending a HTTP error response like it should. Several people suggest this is caused by missing headers or invalid header values in the request.
With the information available it's impossible to say what's going wrong. If you have access to the servers in question you can use packet sniffing tools to find what exactly is sent and received, and look at logs to of the server process to see if there are any error messages.
Summary
This exception is encountered when you are expecting a response, but the socket has been abruptly closed.
Detailed Explanation
Java's HTTPClient, found here, throws a SocketException with message "Unexpected end of file from server" in a very specific circumstance.
After making a request, HTTPClient gets an InputStream tied to the socket associated with the request. It then polls that InputStream repeatedly until it either:
Finds the string "HTTP/1."
The end of the InputStream is reached before 8 characters are read
Finds a string other than "HTTP/1."
In case of number 2, HTTPClient will throw this SocketException if any of the following are true:
The HTTP method is CONNECT
The HTTP method is POST and the client is set to streaming mode
Why would this happen
This indicates that the TCP socket has been closed before the server was able to send a response. This could happen for any number of reasons, but some possibilities are:
Network connection was lost
The server decided to close the connection
Something in between the client and the server (nginx, router, etc) terminated the request
Note: When Nginx reloads its config, it forcefully closes any in-flight HTTP Keep-Alive connections (even POSTs), causing this exact error.
I do get this error when I do not set the Authentication header or I set wrong credentials.
I would suggest using wire shark to trace packets. If you are using Ubuntu, sudo-apt get wireshark. Like Joni stated the only way to figure out whats going wrong is to follow the GET requests and their associated responses.
http://www.wireshark.org/download.html
In my case it was solved just passing proxy to connection. Thanks to #Andreas Panagiotidis.
Proxy proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress("<YOUR.HOST>", 80)));
HttpsURLConnection con = (HttpsURLConnection) url.openConnection(proxy);
In my case url contained wrong chars like spaces . Overall log your url and in some cases use browser.
Most likely the headers you are setting is incorrect or not acceptable.
Example:
connnection.setRequestProperty("content-type", "application/json");
I got this exception too. MY error code is below
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod(requestMethod);
connection.setRequestProperty("Content-type", "JSON");
I found "Content-type" should not be "JSON",is wrong!
I solved this exception by update this line to below
connection.setRequestProperty("Content-type", "application/json");
you can check up your "Content-type"
I'm facing this problem with Java. I want to get some HTML informations from a URL. This code was working for so long, but suddenly, it stopped working.
When I access this URL using the browser, it opens with no problem.
The code:
URL site = new URL(this.url);
java.net.URLConnection yc = site.openConnection();
BufferedReader in = new BufferedReader(new InputStreamReader(yc.getInputStream()));
String inputLine;
String objetivo = "<td height=\"28\" colspan=\"2\"";
while ((inputLine = in.readLine()) != null && !inputLine.contains(objetivo)) {
}
inputLine = in.readLine();
The Exception:
java.io.IOException: Server returned HTTP response code: 500 for URL: http://www.myurl.com
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
at Sites.websites.Site1.getData(Site1.java:53)
at util.Util.lerArquivo(Util.java:278)
at util.Util.main(Util.java:983)
What's wrong? Did the host block me?
HTTP status code 500 usually means that the webserver code has crashed. You need to determine the status code beforehand using HttpURLConnection#getResponseCode() and in case of errors, read the HttpURLConnection#getErrorStream() instead. It may namely contain information about the problem.
If the host has blocked you, you would rather have gotten a 4nn status code like 401 or 403.
See also:
How to use URLConnection to fire and handle HTTP requests?
This Status Code 500 is an Internal Server Error. This code indicates that a part of the server (for example, a CGI program) has crashed or encountered a configuration error.
i think the problem does'nt lie on your side, but rather on the side of the Http server.
the resources you used to access may have been moved or get corrupted, or its configuration just may have altered or spoiled
I had this problem i.e. works fine when pasted into browser but 505s when done through java. It was simply the spaces that needed to be escaped/encoded.
The problem must be with the parameters you are passing(You must be passing blank parameters). For example : http://www.myurl.com?id=5&name=
Check if you are handling this at the server you are calling.
Change the content-type to "application/x-www-form-urlencoded", i solved the problem.
You may look within the first server response and see if the server sent you a cookie.
To check if the server sent you a cookie, you can use HttpURLConnection#getHeaderFields() and look for headers named "Set-Cookie".
If existing, here's the solution for your problem. 100% Working for this case!
In my case, I had changed the Content-Type to Accept and it resolved the issue.
URL url = new URL(GET_URL);
HttpURLConnection con = (HttpURLConnection) url.openConnection();
con.setRequestMethod("GET");
con.setRequestProperty("Accept", "application/json; charset=utf-8");
If it's any help, there is also a similar class in C#'s WebRequest. Although I do not want it in java or .NET, i am wondering how to implement this in native C/C++ code (for windows).
for reference:
try {
URL url=new URL("http://google.ca");
HttpURLConnection con=(HttpURLConnection)url.openConnection();
con.connect();
int code = con.getResponseCode();
System.out.println(code);
} catch (MalformedURLException e) {
System.err.println("Error reading URL.");
}
prints out:
200
meaning "OK"
I understand I probably need to use sockets and send a User-Agent string, but I haven't a clue where to begin. Whenever I learn a new language the first thing I like to do is try porting my code to it, but this one has stumped me.
Any help is appreciated
There is no HTTP support in standard C library.
So you have two options - use 3rd-party HTTP library, such ar libcurl, or handle HTTP yourself:
open socket
resolve hostname
connect to server
build HTTP request
send request to server
receive HTTP response
parse response and get response code from it.