I'm currently calling a local .json file in my Android app using the following line
InputStream inputStream = context.getAssets().open("cyclist.json");
I simply want to switch it to pull the .json from a webservice instead. What is the best way to do this?
Please, please, don't reinvent the wheel.
Use existing libraries Volley by Google (video from I/O talk), Retrofit by Square, RoboSpice and countless others are there to serve you. Further, search before posting
Supposing you already set up a server to respond to requests, I would try something like this:
URL url = new URL("http://www.mydomain.com/slug");
URLConnection urlConnection = url.openConnection();
InputStream in = new BufferedInputStream(urlConnection.getInputStream());
try {
readStream(in);
} finally {
in.close();
}
See URLConnection for details.
I know Android enforces limitations in downloading stuff from a server. You might have to execute the code in another thread, using the AsyncTask. Again, I'm not sure if this is required for your particular purpose.
Related
I am trying to append some information to a text file kept on webserver using java using:
public class Main {
public static void main(String[] args) {
try {
URL url = new URL("http://www.abcd.com/info.txt");
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
if (connection != null) {
System.out.println("Established URL connection");
}
connection.setDoOutput(true);
connection.setRequestMethod("PUT");
connection.setDoInput(true);
connection.setUseCaches(false);
connection.setRequestProperty("Content-Type", "text/html");
System.out.println(connection.getOutputStream().toString());
OutputStreamWriter writer = new OutputStreamWriter(connection.getOutputStream());
writer.write("This is a sample text");
writer.close();
}
catch (Exception ex) {
ex.printStackTrace();
}
}
}
Neither the text file is not being updated nor getting any error.. The reason for doing this is - I have developed a small software and the updates for this will be kept on web site. If any user updates the data, this code will update the text file. This way I will be able to get the information of user who have updated.
As far as I know, you first need to get the data written in the file, to client, Using a GET call , then append the data, and the finally do a POST call to rewrite the file with appended data
You would have to make the changes at server side to do that. You cannot acheive the same using HttpURLConnection.
You can try using FTP if its feasible for you. In case of FTP you should download the file, append the text and upload the same again.
I'm a bit confused - you're attempting to open an HTTP connection to a file and modify it on the fly?
I feel like I might be missing something - plain HTTP doesn't support this. Can you imagine the nightmare it would be if everybody could go around overwriting everybody else's websites (without authentication, even, as your code seems to suggest)?
What you're doing here is calling PUT on the /info.txt resource with your text as the entity body. I'm fairly sure that never has and never will overwrite the corresponding file.
What you need to do is either go through a protocol that supports file writing (WebDav, FTP...) or write server-side code that accepts a content submission (through, for example, a POST or PUT call with an entity body on a specific resource), analyses that input and modify its local file system.
Again, I might be misunderstanding your question entirely, in which case I apologise if I come off as somewhat patronising.
I am trying to download an vcalendar using a java application, but I can't download from a specific link.
My code is:
URL uri = new URL("http://codebits.eu/s/calendar.ics");
InputStream in = uri.openStream();
int r = in.read();
while(r != -1) {
System.out.print((char)r);
r = in.read();
}
When I try to download from another link it works (ex: http://www.mysportscal.com/Files_iCal_CSV/iCal_AUTO_2011/f1_2011.ics). Something don't allow me to download and I can't figure out why, when I try with the browser it works.
I'd follow this example. Basically, get the response code for the connection. If it's a redirect (e.g. 301 in this case), retrieve the header location and attempt to access the file using that.
Simplistic Example:
URL uri = new URL("http://codebits.eu/s/calendar.ics");
HttpURLConnection con = (HttpURLConnection)uri.openConnection();
System.out.println(con.getResponseCode());
System.out.println(con.getHeaderField("Location"));
uri = new URL(con.getHeaderField("Location"));
con = (HttpURLConnection)uri.openConnection();
InputStream in = con.getInputStream();
You should check what that link actually provides. For example, it might be a page that has moved, which gives you back an HTTP 301 code. Your browser will automatically know to go and fetch it from the new URL, but your program won't.
You might want to try, for example, wireshark to sniff the actual traffic when you do the browser request.
I think too that there is a redirect. The browser downloads from ssl secured https://codebits.eu/s/calendar.ics. Try using a HttpURLConnection, it should follow redirects automatically:
HttpURLConnection con = (HttpURLConnection)uri.openConnection();
InputStream in = con.getInputStream();
how do I search for existence of a word in a webpage given its url say "www.microsoft.com". Do I need to download this webpage to perform this search ?
You just need to make http request on web page and grab all its content after that you can search necessary words in it, below code might help you to do so.
public static void main(String[] args) {
try {
URL url;
URLConnection urlConnection;
DataOutputStream outStream;
DataInputStream inStream;
// Build request body
String body =
"fName=" + URLEncoder.encode("Atli", "UTF-8") +
"&lName=" + URLEncoder.encode("Þór", "UTF-8");
// Create connection
url = new URL("http://www.example.com");
urlConnection = url.openConnection();
((HttpURLConnection)urlConnection).setRequestMethod("POST");
urlConnection.setDoInput(true);
urlConnection.setDoOutput(true);
urlConnection.setUseCaches(false);
urlConnection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
urlConnection.setRequestProperty("Content-Length", ""+ body.length());
// Create I/O streams
outStream = new DataOutputStream(urlConnection.getOutputStream());
inStream = new DataInputStream(urlConnection.getInputStream());
// Send request
outStream.writeBytes(body);
outStream.flush();
outStream.close();
// Get Response
// - For debugging purposes only!
String buffer;
while((buffer = inStream.readLine()) != null) {
System.out.println(buffer);
}
// Close I/O streams
inStream.close();
outStream.close();
}
catch(Exception ex) {
System.out.println("Exception cought:\n"+ ex.toString());
}
}
i know how i would do this in theory - use cURL or some application to download it, store the contents into a variable, then parse it for whatever you need
Yes, you need to download page content and search inside it for what you want. And if it happens that you want to search the whole microsoft.com website then you should either write your own web crawler, use an existing crawler or use some search engine API like Google's.
Yes, you'll have to download the page, and, to make sure to get the complete content, you'll want to execute scripts and include dynamic content - just like a browser.
We can't "search" something on a remote resource, that is not controlled by us and no webservers offers a "scan my content" method by default.
Most probably you'll want to load the page with a browser engine (webkit or something else) and perform the search on the internal DOM structure of that engine.
If you want to do the search yourself, then obviously you have to download the page.
If you're planning on this approach, i recommend Lucene (unless you want a simple substring search)
Or you could have a webservice that does it for you. You could request the webservice to grep the url and post back its results.
You could use a search engine's API. I believe Google and Bing (http://msdn.microsoft.com/en-us/library/dd251056.aspx) have ones you can use.
I am attempting to have my android phone connect to my servlet and send it a certain image. The way I figured I would do this, is to use the copyPixelsToBuffer() function and then attempt to send this to the servlet through some output stream(similar to how I would do it in a normal stand alone java application). Will this way work? If so, what kind of stream do I use exactly? Should I just use DataOutputStream and just do something like the following:
ByteBuffer imgbuff;
Bitmap bm = BitmapFactory.decodeResource(getResources(), R.drawable.icon);
bm.copyPixelsToBuffer(bm);
...code...
URLConnection sc = server.openConnection();
sc.setDoOutput(true);
DataOutputStream out = new DataOutputStream( sc.getOutputStream() );
out.write(imgbuff.array());
out.flush();
out.close();
Note: I understand that this may not be the proper way of connecting to a server using the Android OS but at the moment I'm working on just how to send the image, not the connection (unless this is relevant on how the image is sent).
If this is not a way you'd recommend sending the image to the servlet (I figured a byte buffer would be best but I could be wrong), how would you recommend this to be done?
Since a HttpServlet normally listens on HTTP requests, you'd like to use multipart/form-data encoding to send binary data over HTTP, instead of raw (unformatted) like that.
From the client side on, you can use URLConnection for this as outlined in this mini tutorial, but it's going to be pretty verbose. You can also use Apache HttpComponents Client for this. This adds however extra dependencies, I am not sure if you'd like to have that on Android.
Then, on the server side, you can use Apache Commons FileUpload to parse the items out of a multipart/form-data encoded request body. You can find a code example in this answer how the doPost() of the servlet should look like.
As to your code example: wrapping in the DataOutputStream is unnecessary. You aren't taking benefit of the DataOutputStream's facilities. You are just using write(byte[]) method which is already provided by the basic OutputStream as returned by URLConnection#getOutputStream(). Further, the Bitmap has a compress() method which you can use to compress it using a more standard and understandable format (PNG, JPG, etc) into an arbitrary OutputStream. E.g.
output = connection.getOutputStream();
// ...
bitmap.compress(CompressFormat.JPEG, 100, output);
Do this instead of output.write(bytes) as in your code.
How can I post a file to a php using java (as a html form would do) ?
If you simply need to generate an HTTP Post, check out HttpClient, and in particular the PostMethod. Since you're talking HTTP the implementing technology on the server (in your case, PHP) is immaterial.
There's an example here.
It is in fact possible to do a POST using only the classes that are in the JDK, but as others have pointed out it will probably be easier to use a library like HttpClient.
In addition to HttpClient you may also want to look at the client-side java libraries supplied by RESTful frameworks such as Restlet and Jersey. While primarily designed for interacting with web services they offer a very high-level abstraction for GETing and POSTing to just about anything.
Code NOT tested or even compiled (probably doesn't compile), but this is kinda sorta would you'd do if you wanted to roll your own:
URL url = new URL("http://hostname/foo.php");
URLConnection connection = url.openConnection();
connection.setDoInput(true);
connection.setDoOutput(true);
// ignoring possible encoding issues
byte[] body = "param=value¶m2=value2".getBytes();
connection.setRequestProperty("Content-type", "application/x-www-form-urlencoded" );
connection.setRequestProperty("Content-length", String.valueOf(body.length) );
// ignoring possible IOExceptions
OutputStream out = connection.getOutputStream();
out.write(body);
out.flush();
// use this to read back from server
InputStream in = connection.getInputStream();
As you can see, it's pretty low-level stuff. Which is why you want to use a library.
The httpclient library contains all the tools you need to talk to a web server.