I am trying to use core Java to read HTTP request data from an inputstream, using the following code:
BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
String inputLine;
while ((inputLine = in.readLine()) != null)
System.out.println(inputLine);
in.close();
I receive the header fine, but then the client just hangs forever because the server never finds "EOF" of the request. How do I handle this? I've seen this question asked quite a bit, and most solutions involve something like the above, however it's not working for me. I've tried using both curl and a web browser as the client, just sending a get request
Thanks for any ideas
An HTTP request ends with a blank line (optionally followed by request data such as form data or a file upload), not an EOF. You want something like this:
BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
String inputLine;
while (!(inputLine = in.readLine()).equals(""))
System.out.println(inputLine);
in.close();
In addition to the answer above (as I am not able to post comments yet), I'd like to add that some browsers like Opera (I guess it was what did it, or it was my ssl setup, I don't know) send an EOF. Even if not the case, you would like to prevent that in order for your server not to crash because of a NullPointerException.
To avoid that, just add the null test to your condition, like this:
while ((inputLine = in.readLine()) != null && !inputLine.equals(""));
Related
I have a rest http URL from which I have to extract the XML response. When I browse the URL using a browser, it returns html content. My code also sees the same html content instead of XML content.
Is there a way to get the XML content instead of html content? In the below code, I am getting only the html response. But if I check with postman plugin in chrome it shows a nice XML response. How do I get the same response using my code.
public static void sendURL(String urlValue)throws Exception{
URL oracle = new URL("https://whois.arin.net/rest/asn/AS2639");
URLConnection yc = oracle.openConnection();
yc.setRequestProperty("content-type", "application/xml");
BufferedReader in = new BufferedReader(new InputStreamReader(
yc.getInputStream()));
String inputLine;
while ((inputLine = in.readLine()) != null)
System.out.println(inputLine);
in.close();
}
Try to replace this:
yc.setRequestProperty("content-type", "application/xml");
with this:
yc.setRequestProperty("Accept", "application/xml");
Indeed the main purpose is totally different, Content-Type describes what you have in the body of your request while Accept indicates to the server what kind of content the client can manage which is what you want to do.
Content-Type:
The MIME type of the body of the request (used with POST and PUT
requests)
Accept:
Content-Types that are acceptable for the response.
So you already have a stream. What you need to do next is to pass that stream to a library that can decode and parse XML. Try https://docs.oracle.com/javase/7/docs/api/javax/xml/parsers/DocumentBuilder.html#parse(org.xml.sax.InputSource)
UPDATE
Sorry, your initial question was not very clear. If your java invocation of the HTTP request is yielding HTML and the one you want is an XML response, there must be some difference between the HTTP requests you make through the browser and through Java. You can use a tool like TCPMON to sit between your backend and your Java program to capture the raw HTTP request and then compare that with the one you make through the browser.
Since HTTP is a request/response pair, equivalent HTTP requests should always send back the same response.
I found the answer. Updated code. We just need to accept only the xml response.
public static void sendURL(String urlValue)throws Exception{
URL oracle = new URL("https://whois.arin.net/rest/asn/AS2639");
URLConnection yc = oracle.openConnection();
yc.setRequestProperty("accept", "application/xml");
BufferedReader in = new BufferedReader(new InputStreamReader(
yc.getInputStream()));
String inputLine;
while ((inputLine = in.readLine()) != null)
System.out.println(inputLine);
in.close();
}
I have found quite a lot of other posts on this topic but none seem to have the answer I need.
I have written a Bukkit plugin for Minecraft that can send post data to a PHP page and get a return from the page.
Now the one thing I can't figure out. I would like to have a button on the page, and when the button is clicked, send data to the Java plugin and have the plugin print the message.
I have seen something about sockets. But after reading about them I can't figure out how to set them up.
Pretty much at any time you should be able to click the button and it sends data to the Java plugin and I can use that data however I like.
Does anyone know how I can have the Java plugin constantly waiting for data from the page?
My current code:
(This sends the players name to the website.)
String re = "";
URL url = new URL("address here");
URLConnection con = url.openConnection();
con.setDoOutput(true);
PrintStream ps = new PrintStream(con.getOutputStream());
ps.print("player=" + player.getName());
con.getInputStream();
BufferedReader rd = new BufferedReader(new InputStreamReader(con.getInputStream()));
String line;
while ((line = rd.readLine()) != null) {
re += line + "\n";
}
rd.close();
ps.close();
And my php just returns any post data it gets.
It works fine, but I would like to listen in my java plugin for data from the php page.
There are many ways to make communication between two servers. I'd use one of them:
Sockets
JMS - Java Message Service such as ActiveMQ
Both of them have tutorials available, just google.
You could use a database, or setup a json/xml api on the PHP end, and access the database, or access the json/xml from Java with this example code to open the url.
URL url = new URL("site.com/api/foo.json");
try (BufferedReader reader = new BufferedReader(new InputStreamReader(url.openStream(), "UTF-8"))) {
for (String line; (line = reader.readLine()) != null;) {
System.out.println(line);
}
}
You can look at this tutorial to parse JSON with Java.
I am sending commands to a server using http, and I currently need to parse a response that the server sends back (I am sending the command via the command line, and the servers response appears in my browser).
There are a lot of resources such as this: Saving a web page to a file in Java, that clearly illustrate how to scrape a page such as cnn.com. However, since this is a response page that is only generated when the camera receives a specific command, my attempts to use the method described by Mike Deck (in the link above) have met with failure. (Specifically, when my program requests the page again the server returns a 401 error.)
The response from the server opens a new tab in my browser. Essentially, I need to know how to save the current web page using java, since reading in a file is probably the most simple way to approach this. Do any of you know how to do this?
TL;DR How do you save the current webpage to a webpage.html or webpage.txt file using java?
EDIT: I used Base64 from the Apache commons codec, which solved my 401 authentication issue. However, I am still getting a 400 error when I attempt to connect my InputStream (see below). Does this mean a connection isn't being established in the first place?
URL url = new URL ("http://"+ipAddress+"/axis-cgi/record/record.cgi?diskid=SD_DISK");
byte[] encodedBytes = Base64.encodeBase64("root:pass".getBytes());
String encoding = new String (encodedBytes);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("POST");
connection.setDoInput (true);
connection.setRequestProperty ("Authorization", "Basic " + encoding);
connection.connect();
InputStream content = (InputStream)connection.getInputStream();
BufferedReader in = new BufferedReader (new InputStreamReader (content));
String line;
while ((line = in.readLine()) != null) {
System.out.println(line);
}
EDIT 2: Changing the request to a GET resolved the issue.
So while scrutinizing my code above, I decided to change
connection.setRequestMethod("POST");
to
connection.setRequestMethod("GET");
This solved my problem. In hindsight, I think the server was not recognizing the HTTP because it is not set up to handle the various trappings that come along with post.
I am trying to send a request to a server using GET that will respond with XML. I am told that I need to set the "Accept" property, code follows:
StringBuffer url = new StringBuffer(BASE_URL);
url.append(DRS_SERVICE_RELATIVE_URL);
url.append("?").append(DOC_PARAM_NAME).append("=").append(docId);
url.append("&").append(DOB_PARAM_NAME).append("=").append(dob);
try
{
this.server = new URL(url.toString());
URLConnection urlCon = this.server.openConnection();
HttpURLConnection con = (HttpURLConnection)urlCon;
con.addRequestProperty("Accept", "text/xml, application/*+xml, application/xml, text/xml, application/*+xml");
con.connect();
input = new BufferedReader(new InputStreamReader(con.getInputStream()));
String line = null;
while((line = input.readLine()) != null)
System.out.println(line);
I get response code 500. When I talk to the developers of the URL I am trying to access they say I am not setting the "Accept" property to XML? What am I doing wrong? How are you supposed to set that property?
EDIT:
OK this is embarassing. The problem had to do with my development enviroment, specifically the way I set up a TCP/IP monitoring tool. When I stopped monitoring the network messages it worked as expected.
The problem had to do with my development enviroment, specifically the way I set up a TCP/IP monitoring tool. When I stopped monitoring the network messages it worked as expected.
I have started a small project in Java.
I have to create a client which will send xml to a url as a HTTP POST request.
I try it using java.net.* package (Following is the piece of code) but I am getting error as follows:
java.io.IOException: Server returned HTTP response code: 500 for URL: "target url"
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1441)
at newExample.main(newExample.java:36)
My code is as follows:
try {
URL url = new URL("target url");
URLConnection connection = url.openConnection();
if( connection instanceof HttpURLConnection )
((HttpURLConnection)connection).setRequestMethod("POST");
connection.setRequestProperty("Content-Length", Integer.toString(requestXml.length()) );
connection.setRequestProperty("Content-Type","text/xml; charset:ISO-8859-1;");
connection.setDoOutput(true);
connection.connect();
// Create a writer to the url
PrintWriter writer = new PrintWriter(new
OutputStreamWriter(connection.getOutputStream()));
// Get a reader from the url
BufferedReader reader = new BufferedReader(new
InputStreamReader(connection.getInputStream()));
writer.println();
writer.println(requestXml);
writer.println();
writer.flush();
String line = reader.readLine();
while( line != null ) {
System.out.println( line );
line = reader.readLine();
}
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Please help with suitable examples or any other ways of doing this.
Point errors/mistakes in above code or other possibilities.
My Web Service is in spring framework
xml to send is in the string format: requestXml
The problem lies in below code
// Get a reader from the url
BufferedReader reader = new BufferedReader(new
InputStreamReader(connection.getInputStream()));
As the service might not always return you the proper response... as you are calling a service through http, it can be possible that the server itself is not available or the service is not available. So you should always check for the response code before reading response from streams, based on the response code you've to decide whether to read it from inputStream for success response or from errorStream for failure or exception condition.
BufferedReader reader = null;
if(connection.getResponseCode() == 200)
{
reader = new BufferedReader(new
InputStreamReader(connection.getInputStream()));
}
else
{
reader = new BufferedReader(new
InputStreamReader(connection.getErrorStream()));
}
This would resolve the problem
The problem is inside your server code or the server configuration:
10.5.1 500 Internal Server Error
The server encountered an unexpected condition which prevented it from fulfilling the request.
(w3c.org/Protocols)
If the server is under your control (should be, if I look at the URL [before the edit]), then have a look at the server logs.
Well, you should close your streams and connections. Automatic resource maangement from Java 7 or http://projectlombok.org/ can help. However, this is probably not the main problem.
The main problem is that the server-side fails. HTTP code 500 means server-side error. I can't tell you the reason, because I don't know the server side part. Maybe you should look at the log of the server.
I think that your problem is that you are opening the input stream before you have written and closed the output stream. Certainly, the Sun Tutorial does it that way.
If you open the input stream too soon, it is possible that the output stream will be closed automatically, causing the server to see an empty POST request. This could be sufficient to cause it to get confused and send a 500 response.
Even if this is not what is causing the 500 errors, it is a good idea to do things in the order set out in the tutorial. For a start, if you accidentally read the response before you've finished writing the request, you are likely to (at least temporarily) lock up the connection. (In fact, it looks like your code is doing this because you are not closing the writer before reading from the reader.)
A separate issue is that your code does not close the connection in all circumstances, and is therefore liable to leak network connections. If it does this repeatedly, it is likely to lead to more IOExceptions.
If you are calling an External Webservice and passing a JSON in the REST call, check the datatype of the values passed.
Example:
{ "originalReference":"8535064088443985",
"modificationAmount":
{ "amount":"16.0",
"currency":"AUD"
},
"reference":"20170928113425183949",
"merchantAccount":"MOM1"
}
In this example, the value of amount was sent as a string and the webservice call failed with Server returned HTTP response code: 500.
But when the amount: 16.0 was sent, i.e an Integer was passed, the call went through. Though you have referred API documentation while calling such external APIs, small details like this could be missed.