I need to make an HTTP request to a resource that looks like "xy:index.html" in Java.
The HTTP implementation does not have to be sophisticated. I just need to be able to do this to avoid same-origin violations when running in development mode for a GWT app by forwarding HTTP requests on the server-side to the "xy" protocol.
Any clues about how I may be able to do this would be extremely appreciated. I feel like I'm a bit out of my league on this one ;)
I'm not sure if I understand the question properly but perhaps you can register a URL handler. This link has some info about how to do that. Perhaps you can register a custom handler for the xy: protocol and re-use the HTTP URL handlder for the real work.
Related
I am not looking specific answer, just an idea or a tip.
I have following problem:
Android application is a client for web service. It has a thread, which sends events (XML form with request ID) through http protocol and for every request server sends confirmation, that he understand message right with granted event ID - server is a synchronizer for few clients. I want use websocket protocol to send events through websocket too but it is a little bit tricky - instead of http, I don't expect to get response for every request. Moreover, incoming websocket messages is parsed in other thread. Primary mechanism it's a little bit overgrown and I don't want to write everything from scratch.
I want to make this asynchronous websocket mechanism to pretend to be synchronous.
There is my idea for now - after send event through websocket I will wait no more for e.g 5 seconds for response which will processed in other thread (it's came as XML) and regarding too request ID it will notify proper paused thread. I worry Condition.await() and condition.signal isn't the best idea, what do you think?
According to this problem, I've realized that I have problems with project this kind of mechanism. Do you have an idea, where can I find information about good pattern and tips which good to now to avoid bad approach? Thanks in advance!
The only difference between websocket and HTTP requests is the lack of HTTP headers when a message comes in. In websocket, you have a heartbeat that keeps the connection alive and allows full duplex communication, and then you have pure payloads. It's your job to find which message headers you will use to route the requests properly in your server/client.
So, that doesn't stop you from communicating in a request/response manner by simply writing to the output stream right after receiving. I suggest you take a look at the RFC
https://www.rfc-editor.org/rfc/rfc6455
If you're a little more visual, this slideshow can help:
http://www.slideshare.net/sergialmar/websockets-with-spring-4
Or if you want some more serious implementations as an example, take a look at spring's docs:
http://docs.spring.io/spring/docs/current/spring-framework-reference/html/websocket.html
My task is to load web site in WebView over HTTPS with unsupported by vanilla Android TLS cipher.
Right now as proof of concept I have implemented apache http client capable of doing http requests to such resources.
What is the best approach to make WebView use my custom client implementation to do all network requests?
Actually, the accepted answer is wrong. You do not get full information; what's missing are request bodies.
So you can implement GET or HEAD requests just fine, but POST requests are trickier.
I haven't seen a good solution for that yet. One I've come across uses JavaScript inserted into the page to collect the POST data, hand it to Java via a binding https://developer.android.com/guide/webapps/webview.html#BindingJavaScript and then performs the request in Java.
Unfortunately, the WebView will try to perform the same request again, so you need to add more hackery to make it work.
Since Android 5.0 (API 21+) you can use WebViewClient.shouldInterceptRequest(WebView, WebResourceRequest) to intercept web requests with full information and perform them with custom HTTP client.
Thanks #Stan for the tip.
I'm a little unfamiliar both with the Servlet API and Apache Http Components.
I need to handle an incoming POST request with unknown data (although probably the result of a form submission) using HttpServlet.doPost() which I've implemented, and request the same posted information from another URL, effectively acting as a relay for the HTTP POST. I then need to convert the response to a String (it will be text/html) and process it further before returning it to the web browser that requested it from me.
Due to my unfamiliarity with these libraries, its not clear to me how to handle issues like the content-type of the posted data, and also avoiding any problems due to neglecting to release resources.
Can anyone provide any pointers on this?
You should start by having a look at HttpClient class from apache API.
It will handle both get and posts as needed and later you could feel its request with the data you receive in your own servlet.
How can I make a java-based application server reply with an empty-valued response header, like this?
content-length:\r\n
Unfortunately when I call
response.setHeader("Content-Length", len)
where len is either an empty string or null, the response will not include the header.
I've checked the HttpServletResponse and HttpServletResponseWrapper javadocs but couldn't figure out what could be overriden to provide my custom behaviour.
Background
I'm building a testing application that is supposed to emulate badly-behaved HTTP server scenarios. The application is supposed to reply to requests with preset pages and HTTP headers, including malformed ones like the above case.
The application is written in grails.
I'm building a testing application that is supposed to emulate badly-behaved HTTP server scenarios.
In such a case, attempting to get a well-behaving server to mimic such behavior is a bad idea. If you need to mimic a bad server, or a particular set of scenarios you wish to test, then you may do one of the following:
write a custom application that listens on a particular port (using the ServerSocket class) that will respond with malformed HTTP headers. Using HTTP libraries may not help, for libraries may have code to detect erroneous conditions and correct them automatically.
use a HTTP proxy that is capable of intercepting responses and allows for modifications of these responses. You will find several if you Google for "http debugging proxy", but if you haven't heard of any, I would suggest looking at Fiddler, WebScarab or Burp.
You can try a tool like SoapUI or Fiddler with it's Firefox extension. I havent tried setting a malformed header with them but I wouldn't be suprised if you could.
Something not clear for me: your application is written in Grails, but you are discussing of javadocs... Well, I suppose you try to create a bad server in JAVA...
As you said, answering with "Content-Length:\r\n" is not legal for HTTP. You must put an integer value or discard the header. I think setHeader() helps you to avoid to produce an illegal HTTP message.
You can workaround this way creating manually the headers (you can write directly to the socket without using the setHeader blocks).
Other solution is to create a filter (in addition of your servlet) with your own implementation of HttpServletResponse. You will pass this implementation to the servlet.
Is it possible to send "100 Continue" HTTP status code, and then later some other status code after processing entire request using Java Servlet API (HttpServletResponse)?
I can't find any definitive "No" answer, although API doesn't seem to support it.
I assume you mean "100 Continue".
The answer is: no, you can't (at least not the way it's intended, as provisional response). In general, the servlet engine will do it automatically, when the request requires it. Of course this makes it impossibe for the servlet to prevent sending the 100 status -- this issue is a known problem in the Servlet API, and has been known for what feels like eons now.
I know that Jetty will wait until getReader() or getInputStream() is called before it sends a 100. I think this is the behavior you are looking for. I don't know what Tomcat does.
Did you mean to ask How do I send a status code before the complete request is received, to interrupt an in-progress request due to a missing header field? It seems that's not possible with standard servlets.
What server are you using?
Some server's servlet extensions may allow this, e.g. Tomcat's Comet servlet might send EventType.BEGIN once the headers are available to process, which may allow you to interrupt a PUT that doesn't have the correct authentication.
Alternatively your server might have a plugin to reject requests based on headers.
Do you mean status code 100 ?
The API does support sending SC_CONTINUE.