I'm implementing some simple java class in order to send an HTTP Request with POST method and also another java class in order to receive it.
The server works fine when I make a POST request by means of my browser(Chrome), or an application(I have used Postman in this case) but it ends up with problem when I send HTTP Request with java!
My sending HTTP class is "Sender.java", containing the following snippet:
String url = "http://localhost:8082/";
URL obj = new URL(url);
HttpURLConnection con = (HttpURLConnection) obj.openConnection();
// Setting basic post request
con.setRequestMethod("POST");
//con.setRequestProperty("Accept-Language", "en-US,en;q=0.5");
//con.setRequestProperty("Content-Type","text/plain");
// Send post request
con.setDoOutput(true);
OutputStream os = con.getOutputStream();
os.write("Just Some Text".getBytes("UTF-8"));
os.flush();
os.close();
//connect to the Server(resides at Server.java)
con.connect();
I have commented some lines of code setting Headers like "Accept-Language" and "Content-Type" because I don't know whether or not are these headers required for the java program to work out?
The server is another java program named "Server.java". Here is the snippet related to reading HTTP Request made by the Sender.java(if need be).
int servPort = 8082;
// Create a server socket to accept HTTP client connection requests
HttpServer server = HttpServer.create(new InetSocketAddress(servPort), 0);
System.out.println("server started at " + servPort);
server.createContext("/", new PostHandler());//PostHandler implements HttpHandler
server.setExecutor(null);
server.start();
All I want is to send a plaintext as the body of my HTTP Request with the Post method. I have read plenty of sites and even related questions at this site. But it still doesn't work out. In other words, whenever I create an HTTP Request from "Sender.java", nothing appears at "Server.java". I just want to know what's wrong with my snippets and how should I fix that?
I tested this and it's working:
//Sender.java
String url = "http://localhost:8082/";
URL obj = new URL(url);
HttpURLConnection con = (HttpURLConnection) obj.openConnection();
con.setRequestMethod("POST");
con.setDoOutput(true);
OutputStream os = con.getOutputStream();
os.write("Just Some Text".getBytes("UTF-8"));
os.flush();
int httpResult = con.getResponseCode();
con.disconnect();
As you can see, connect is not necessary. The key line is
int httpResult = con.getResponseCode();
When you send a POST form using the browser, it sends the form in a certain format, defined in RFC1866, you have to recreate this on Java when making a post request.
With this format, its important you set the Content-Type header to application/x-www-form-urlencoded, and pass the body as you would do in a url with a get request.
Borrowing some code of my previous answer to POST in Java:
URL obj = new URL(url);
HttpURLConnection con = (HttpURLConnection) obj.openConnection();
// Setting basic post request
con.setRequestMethod("POST");
Map<String,String> form = new HashMap<>();
// Define the fields
form.put("username", "root");
form.put("password", "sjh76HSn!"); // This is a fake password obviously
// Build the body
StringJoiner sj = new StringJoiner("&");
for(Map.Entry<String,String> entry : arguments.entrySet())
sj.add(URLEncoder.encode(entry.getKey(), "UTF-8") + "="
+ URLEncoder.encode(entry.getValue(), "UTF-8"));
byte[] out = sj.toString().getBytes(StandardCharsets.UTF_8);
int length = out.length;
// Prepare our `con` object
con.setFixedLengthStreamingMode(length);
con.setRequestProperty("Content-Type", "application/json; charset=UTF-8");
con.connect();
try (OutputStream os = con.getOutputStream()) {
os.write(out);
}
Maybe “localhost” in the sender url does not resolve to the same ip that the server binds to? Try changing to 127.0.0.1 or your actual IP address.
try with PrintStream
String url = "http://localhost:8082/";
URL obj = new URL(url);
HttpURLConnection con = (HttpURLConnection) obj.openConnection();
// Setting basic post request
con.setRequestMethod("POST");
//con.setRequestProperty("Accept-Language", "en-US,en;q=0.5");
//con.setRequestProperty("Content-Type","text/plain");
// Send post request
con.setDoOutput(true);
OutputStream os = con.getOutputStream();
java.io.PrintStream printStream = new java.io.PrintStream(os);
printStream.println("Just Some Text");
con.getInputStream();//Send request
os.flush();
os.close();
Related
I'm trying make a request with Java, when I call it using cURL like this, it works:
curl -X PUT http://serverurl.com/method/6eb276a2-5c79-4f6e-a4b5-a26b0e6848c7/action -H 'Content-Type: application/json' -H 'Token: cba5f12c-af55-480f-970e-525e446ef153' -H 'Content-Length : 0'
If I call the same request without passing header Content-Length param, I get 411 HTTP error, length required.
This is my code in Java:
URL url = new URL("http://serverurl.com/method/6eb276a2-5c79-4f6e-a4b5-a26b0e6848c7/action");
HttpURLConnection con = (HttpURLConnection) url.openConnection();
con.setRequestMethod("PUT");
con.addRequestProperty("Content-Type", "application/json");
con.addRequestProperty("Token", "cba5f12c-af55-480f-970e-525e446ef153");
con.connect();
This request is getting a 411 HTTP code response. So, I tryed to add:
con.addRequestProperty("Content-Length", "0");
But it doesn't work, so I changed to:
URL url = new URL("http://serverurl.com/method/6eb276a2-5c79-4f6e-a4b5-a26b0e6848c7/action");
HttpURLConnection con = (HttpURLConnection) url.openConnection();
con.setRequestMethod("PUT");
con.addRequestProperty("Content-Type", "application/json");
con.addRequestProperty("Token", "cba5f12c-af55-480f-970e-525e446ef153");
con.setDoOutput(true);
con.getOutputStream().close();
con.setFixedLengthStreamingMode(0);
con.connect();
But now I'm getting 400 HTTP code.
How can I do a PUT request with an empty body and setting content length to match the cURL call?
using the HttpUrlConnection, you should use the setRequestProperty method to add headers to your request. I can see your using the "addRequestProperty" which is probably why its not working. But refer to this link for more info https://juffalow.com/java/how-to-send-http-get-post-request-in-java and heres some code that i use to for a put request
URL url = new URL(BASE_URL+"/"+userID+".json");
urlRequest = (HttpURLConnection) url.openConnection();
urlRequest.setDoOutput(true);
urlRequest.setRequestMethod("PUT");
urlRequest.setRequestProperty("Content-Type", "application/json;
charset=UTF-8");
OutputStream os = urlRequest.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os, "UTF-8");
osw.write("{\"idToken\":\""+"token"+"\"}");
osw.flush();
osw.close();
urlRequest.connect();
JsonParser jp = new JsonParser(); //from gson
JsonElement root = jp.parse(new InputStreamReader((InputStream)
urlRequest.getContent()));//Convert the input stream to a json element
JsonObject rootobj = root.getAsJsonObject();//Maybe an array or object
well thats just sample what i use... and i hope this works for you. Happy coding.
My server sends a response to an HTTPUrlConnection in this manner:
ServerSocket servSok = new ServerSocket(portNmb);
Socket sok = servSok.accept();
processTheIncomingData(sok.getInputStream());
Writer wrtr = new OutputStreamWriter(sok.getOutputStream());
wrtr.write("<html><body>123 Hello World</body></html>"); // <------- format?
wrtr.flush();
the client
HttpURLConnection conn = (HttpUTLConnection) url.openConnection();
conn.setRequestMethod("GET");
conn.setDoOutput(true);
conn.setDoInput(true);
sendSomeData(conn.getOutputStream());
String mssg = conn.getResponseMessage(); // <----- Invalid Http Response
conn.getResponseCode() also gives the same "Invalid http response."
I agree with #JBNizet. HTTP is a very complex protocol. You should use a server.
But if you are writing this for a toy project, here is some code to get you started.
Do not use any of this in production :)
String content = "<html><body>123 Hello World</body></html>";
Writer wrtr = new OutputStreamWriter(sok.getOutputStream());
wrtr.write("HTTP/1.1 200 OK\n");
wrtr.write("Content-Type: text/html; charset=UTF-8\n");
//assuming content is pure ascii
wrtr.write("Content-Length: " + content.length() + "\n");
wrtr.write("Connection: close\n\n");
wrtr.write(content);
wrtr.flush();
//then close the connection, do not reuse the connection
//as you might not have consumed the full request content
I have a server that takes a POST request and answers with a data stream. I have seen that on URL I can open a connection or a stream. A stream, however, has no method for writing out data:
URL url = new URL("...");
url.openConnection(); //either I open a connection which has a output stream, but no input
url.openStream(); //or I open a stream, but I cannot write anything out
How can I solve this problem elegantly?
Sample code snippet to use OutputStream.
Note: You can set content types & send some URL parameters to the URL only.
URL obj = new URL(url);//some url
HttpURLConnection con = (HttpURLConnection) obj.openConnection();
con.setDoOutput(true);
DataOutputStream wr = new DataOutputStream(con.getOutputStream());
String urlParams = "fName=xyz&lname=ABC&pin=12345"; // some parameters
wr.writeBytes(urlParams);
wr.flush();
wr.close();
Have a look at detailed explanation in this article1 and article2
I am trying to use a for loop to send multiple POST requests through a DataOutputStream and then close it. At the moment, only the first index of the "trades" array list is sent to the website. Any other indexes are ignored and I'm assuming they are not being sent. I wonder if I am properly flushing the stream? Thank you!!!
Examples of trades values: "101841599", "101841801"
Example of code value: 85e4c22
Snippet of my code:
private ArrayList<String> trades = new ArrayList<String>();
private String code;
String url = "http://www.dota2lounge.com/ajax/bumpTrade.php";
URL obj = new URL(url);
HttpURLConnection con = (HttpURLConnection) obj.openConnection();
con.setRequestMethod("POST");
con.setRequestProperty("Accept-Language", "en-US,en;q=0.8");
con.setRequestProperty("Cookie", cookie);
con.setDoOutput(true);
DataOutputStream wr = new DataOutputStream(con.getOutputStream());
for(int i=0; i<trades.size(); i++){
wr = new DataOutputStream(con.getOutputStream());
wr.writeBytes("trade=" + trades.get(i) + "&code=" + code);
wr.flush();
System.out.println("again");
}
wr.flush();
wr.close();
It turns out I had to actually get the response for it to properly close the connection before I started a new one. Appending these lines to the end of the for loop fixed the issue:
int nothing = con.getResponseCode();
String morenothing = con.getResponseMessage();
From the HttpURLConnection javadoc:
"Each HttpURLConnection instance is used to make a single request but the underlying network connection to the HTTP server may be transparently shared by other instances."
So if you want to send multiple requests, then for each request call obj.openConnection(), set the connection settings, open the OutputStream, and write the data. Your Java runtime is permitted to keep the actual connection open to save time and bandwidth.
Here is my code:
String addr = "http://172.26.41.18:8080/domain/list";
URL url = new URL(addr);
HttpURLConnection httpCon = (HttpURLConnection) url.openConnection();
httpCon.setDoOutput(true);
httpCon.setDoInput(true);
httpCon.setUseCaches(false);
httpCon.setAllowUserInteraction(false);
httpCon.setRequestMethod("GET");
httpCon.addRequestProperty("Authorization", "Basic YWRtaW4fYFgjkl5463");
httpCon.connect();
OutputStreamWriter out = new OutputStreamWriter(httpCon.getOutputStream());
System.out.println(httpCon.getResponseCode());
System.out.println(httpCon.getResponseMessage());
out.close();
What I see in response:
500 Server error
I open my httpCon var, and what I see:
POST /rest/platform/domain/list HTTP/1.1
Why is it set to POST even though I have used httpCon.setRequestMethod("GET"); to set it to GET?
The httpCon.setDoOutput(true); implicitly set the request method to POST because that's the default method whenever you want to send a request body.
If you want to use GET, remove that line and remove the OutputStreamWriter out = new OutputStreamWriter(httpCon.getOutputStream()); line. You don't need to send a request body for GET requests.
The following should do for a simple GET request:
String addr = "http://172.26.41.18:8080/domain/list";
URL url = new URL(addr);
HttpURLConnection httpCon = (HttpURLConnection) url.openConnection();
httpCon.setUseCaches(false);
httpCon.setAllowUserInteraction(false);
httpCon.addRequestProperty("Authorization", "Basic YWRtaW4fYFgjkl5463");
System.out.println(httpCon.getResponseCode());
System.out.println(httpCon.getResponseMessage());
See also:
Using java.net.URLConnection to fire and handle HTTP requests
Unrelated to the concrete problem, the password part of your Authorization header value doesn't seem to be properly Base64-encoded. Perhaps it's scrambled because it was examplary, but even if it wasn't I'd fix your Base64 encoding approach.