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Java post http request (express) REST api

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

HttpResponse code not 200

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.

When does HttpURLConnection on Android really call the request

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 )

How to know if HttpURLConnection actually sent the request out on the underlying socket?

AFAIK HttpURLConnection doesn't actually send the request out until we attempt to read the input. However, if an exception happens here I can't differentiate between the case where the request was not sent, and the case where the request was sent but some other sort of error occurred (maybe we entered a tunnel so couldn't receive the response).
Is there a way to query and find out if the request was actually sent or not?

You might have some luck with
URL url = new URL(serverUrl);
connection = (HttpURLConnection) url.openConnection();
// write to connection output stream (don't forget to flush())
connection.getResponseCode();
You can get a full list of response codes at http://download.oracle.com/javase/1,5.0/docs/api/java/net/HttpURLConnection.html
Having said that I can imagine your data going out completely an instant before you enter a tunnel and the connection not having a response code set, in which case you would try to send again (perhaps using a unique 'send id') so that the listener knows to ignore you resend but can still let you know that it was received.

java.io.IOException: Server returned HTTP response code: 500

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");