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.
Related
I am loading model in apache jena using function FileManager.get().loadModel(url).And I also know that there may be some URLs in HTTP Response Link Header .I want to load model also from the links(URLs) in link header.How to do that ? Is there any inbuilt fuctionality to get access to header and process link header in Response header?
FileManager.get().loadModel(url) packages up reading a URL and parsing the results into a model. It is packing up a common thing to do; it is not claiming to be comprehensive. It is quite an old interface.
If you wanted detailed control over the HTTP handling, see if HttpOp (a lower level) mechanism helps, otherwise do the handling in the application and hand the input stream for the response directly to the parser.
You may also find it useful to look at the code in RDFDataMgr.process for help with content negotiation.
I don't think that this is supported by Jena. I don't see any reason in doing so. The HTTP request is done to get the data and maybe also to get the response type. If you want to get the URLs in some header fields, why not simply use plain old Java:
URL url = new URL("http://your_ontology.owl");
URLConnection conn = url.openConnection();
Map<String, List<String>> map = conn.getHeaderFields();
i need to send a xml request in java and catch the response.
How can i do this ?
I search in the google but nothing solid until now.
Best regards,
Valter Henrique.
If you are looking to do an HTTP POST, then you could use the java.net.* APIs in Java SE:
try {
URL url = new URL(URI);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setDoOutput(true);
connection.setInstanceFollowRedirects(false);
connection.setRequestMethod("POST");
connection.setRequestProperty("Content-Type", "application/xml");
OutputStream os = connection.getOutputStream();
// Write your XML to the OutputStream (JAXB is used in this example)
jaxbContext.createMarshaller().marshal(customer, os);
os.flush();
connection.getResponseCode();
connection.disconnect();
} catch(Exception e) {
throw new RuntimeException(e);
}
XML is a data format. If you talk about requests/responses, you need to know the protocol.
My guess is that the protocol you are using is HTTP(S) and you have to do a POST with your XML request, but this is just an educated(?) guess.
You can use playframework. It is the easiest web framework I have ever used in Java. It is resembles to rails but in java. Give it a try.
http://www.playframework.org/
It has a nice and easy to use template engine based on groovy. You can set a request format as described here.
http://www.playframework.org/documentation/1.1/routes
Go for documentation for details. You will implement your first website that can send and get requests in just hours.
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.
I am decoding http packets.
And I faced a problem that chunk problem.
When I get a http packet it has a header and body.
When transefer-encoding is chunked I don't know what to do ?
Is there a useful API or class for dechunk the data in JAVA ?
And if someone , experienced about http decoding , please show me a way how to do this ?
Use a fullworthy HTTP client like Apache HttpComponents Client or just the Java SE provided java.net.URLConnection (mini tutorial here). Both handles it fully transparently and gives you a "normal" InputStream back. HttpClient in turn also comes with a ChunkedInputStream which you just have to decorate your InputStream with.
If you really insist in homegrowing a library for this, then I'd suggest to create a class like ChunkedInputStream extends InputStream and write logic accordingly. You can find more detail how to parse it in this Wikipedia article.
Apache HttpComponents
Oh, and if we are talking about the client side, HttpUrlConnection does this as well.
If you are looking for a simple API try Jodd Http library (http://jodd.org/doc/http.html).
It handles Chunked transfer encoding for you and you get the whole body as a string back.
From the docs:
HttpRequest httpRequest = HttpRequest.get("http://jodd.org");
HttpResponse response = httpRequest.send();
System.out.println(response);
Here is quick-and-dirty alternative that requires no dependency except Oracle JRE:
private static byte[] unchunk(byte[] content) throws IOException {
ByteArrayInputStream bais = new ByteArrayInputStream(content);
ChunkedInputStream cis = new ChunkedInputStream(bais, new HttpClient() {}, null);
return readFully(cis);
}
It uses the same sun.net.www.http.ChunkedInputStream as java.net.HttpURLConnection does behind the scene.
This implementation doesn't provide detailed exceptions (line numbers) on wrong content format.
It works with Java 8 but could fail in with next release. You've been warned.
Could be useful for prototyping though.
You can choose any readFully implementation from Convert InputStream to byte array in Java.
I'm building an Eclipse plugin that talks to a REST interface which uses Basic Authentication. When the authentication fails I would like to popup my plugin's settings dialog and retry. Normally I could use the static Authenticator.setDefault() to setup an authenticator for all HttpURLConnection's for this, but since I am writing a plugin I don't want to overwrite Eclipse's default Authenticator (org.eclipse.ui.internal.net.auth);
I thought of setting my custom Authenticator before loading and putting Eclipse's default back afterwards, but I imagine this will cause all sorts of race issues with multithreading so I quickly lost that notion.
Google searches yield all sorts of results basically telling me it's not possible:
The Java URLConnection API should have a setAuthenticator(Authenticator) method for making it easier to use this class in multi-threaded context where authentication is required.
Source
If applications contains few third party plugins and each plugin use its own Authenticator what we should do? Each invocation of "Authenticator.setDefault()" method rewrite previously defined Authenticator...
Source
Are there any different approaches that might help me overcome this issue?
If it is not possible with HttpURLConnection I would suggest using the httpclient library from Apache.
A quick example:
HttpClient client = new HttpClient();
client.getState().setCredentials(AuthScope.ANY, new UsernamePasswordCredentials("test","test"));
GetMethod getMethod = new GetMethod("http://www.example.com/mylogin");
client.executeMethod(getMethod);
System.out.println(getMethod.getResponseBodyAsString());
Another approach would be to perform the basic authentication yourself on the connection.
final byte[] encodedBytes = Base64.encodeData((username + ':' + new String(password)).getBytes("iso-8859-1"));
final String encoded = new String(encodedBytes, "iso-8859-1");
connection.setRequestProperty("Authorization", "Basic " + encoded);
This would also have the advantage of not requiring an unauthenticated request to receive a 401 before providing the credential on a subsequent request. Similar behavior can be leveraged in the apache http-client by requesting preemptive authentication.