I have a file, sample.xml located at one web server. I want to access this file from a GWT application running at another server. I dont want to make RPC calls to the same server serving GWT application and access the required file on server side (like a proxy). I want to access the file directly from client side as my application is going to be hosted as static files in a web server.
Is there a way to do that?
Sure - you must issue a XHR (XmlHTTPRequest) from the browser, and then parse the data.
In GWT you can do it using the RequestBuilder class (see here).
Please note that some client side restrictions may apply (e.g. Single Origin Policy etc.)
You issue the request (GET or POST - GET in your case) and pass a callback instance.
The instance's onResponseReceived method receives a Response object, which by calling its getText method returns the received contents.
You're trying to have your website (a.com/index.html) reference b.com/sample.xml. I see a few options.
If you have access to b.com's servers:
Edit sample.xml into sample.js to contain the same information in JSON with a callback, and reference it with a script tag
Compile your website using the cross-site loader (see Controlling Compiler Output), put your index.html at b.com/index.html, put all the rest of your files on a.com. Then all your RPC calls can go to b.com, but this means the user would have to navigate to b.com instead of a.com
If you don't have access to b.com's servers:
- Simply provide a link for people to download sample.xml
- Host a.com on a server with some kind of script support (PHP, Python, Ruby, Java, anything) and put a proxy to b.com/sample.xml
Related
I am wondering if the server can initiate the connection to the client after it has served ordinary html file via GET request?
More specifically I have set up webpack development server and all browser refresh after I change files work, but I cannot find any bootstrapping in the client. I see there are no special embedded script tags or any inline script or anything that can trigger the communication, yet I get the web socket in my network tab. Maybe I just got it all wrong and there is some trigger that I cannot find?
According to the comment it's not possible to initiate the web-scoket connection from the server and I have managed to figure out what happens with the webpack-dev-server.
It injects a special module (or rather a lot of them) and calls it during the initialization right before your entry point is executed.
webpackJsonp([1],{
/***/ 1:
function(module, exports, __webpack_require__) {
// Here is the module that connects to the dev-server
__webpack_require__("./node_modules/webpack-dev-server/client/index.js?http:/localhost:8080");
// This is your entry point
module.exports = __webpack_require__("./Source/main.ts");
}
},[1]);
P.S. I have used webpack.NamedModulesPlugin() to get the proper names for the modueles instead of numbers to understand what's going on.
I know how to use JSON in dart also communicating with a server using the HttpRequest API from the dart:html library and parsing JSON data using the dart:convert !!https://www.dartlang.org/articles/json-web-service/
I am looking for Dynamic content loading using Ajax asynchronous methods or calls in DART! ..
like .. the web page need to load content dynamically if there is any change or update in JSON files in server! ..
And how to do this in Angular Dart!?
There's no way to be notified when something changes on the server without either a) polling for changes (this can be pretty wasteful) or b) having the server notify you.
For (a), you could create a periodic timer that fetches the JSON or checks whether it's been updated (you'd need some way of checking this with the server).
A better fit would be something like Web Sockets, with the server able to push your JSON to the client whenever it changes. However, this is quite an architecture change from pulling JSON from the server, because you would need to be holding web sockets open between the server and all clients that have the page loaded, so the server can send the data to them all whenever it changes.
There are some samples of using Web Sockets on the Dart site; but bear in mind you'll need something on the server, this won't work if you only have access to the client.
I have an application which at one point wants to launch a particular URL in the default browser. This is pretty simple and can be achieved using ShellExecute on Windows. However the catch is that the server expects some additional custom header information (for authentication/identification purposes) to be sent along with the GET request.
Is there any way by which this (additional header) information could be passed to the browser while launching it?
Note:- I want to launch the default browser and not use a Web browser control
As I understand you have only one option: add intermidiate page (in internet or on localhost).
You have to create yoursite.com/sendHeaders.php or localhost/sendHeaders.php (or any another extension; choose language what do you prefer), which does following:
Unpack parameters (URL and headers),
Connect to the URL, send the headers,
Print the answer in browser.
So you will open in your browser intermediate page yoursite.com/sendHeaders.php?url=realUrl&headers=packedHeaders, but browser will show you a page realUrl, which received proper headers.
Can anyone guide me for setting up suffix proxy server , so that user can access some specific sites cached in our campus server without doing any configuration in their browsers.
by suffix proxy i mean that if user wants to open http: //en.wikipedia.org/wiki/Proxy_server page then he should enter link:
http ://en.wikipedia.org.CAMPUSPROXY.NET/wiki/Proxy_server (where campusproxy.net is our proxy server) and this requested page can be retrived from our proxy server in place of wikipedia.org
It's a redirect really - your server needs to have a url check that will catch the prefix portion of the url and for this you obviously need unlimited prefix's available from the registered domain URI then it just reforms the uri of the prefix makes the request for the page and then presents it as content to the user - normally you'll also inject a banner at the top of the page also.
so it goes
User - http-get en.wikipedia.org.CAMPUSPROXY.NET/wiki/Proxy_server
your server takes this and creates "en.wikipedia.org/wiki/Proxy_server" via a script or what have you.
CAMPUSPROXY.NET http-get en.wikipedia.org/wiki/Proxy_server
inject the banner code into the webpage via a script or what have you.
probably also modify the html tags and headers to include your prefix proxy info
some knowledge of python - perl or whatever is all you need together with apache or similar server, their are of course scripts out there already but if you do that you'll learn nothing.
I'm new and just developing on J2EE.
I am modifying an existing application (an OpenSource project).
I need to save an image on a client sent by the server, but I do not know how.
This activity must be done in a transparent manner without affecting the existing operation of the application.
From the tests done I get this error:
java.lang.IllegalStateException: getWriter () has Already Been Called for this response.
How should carry out this task, according to your own opinion?
How do I save on the client, locally, the image?
Update:
Thanks for the answers.
My problem is that:
the image is generated on the server, but not for direct client request (there is no link to click on web page), the picture is composed using other services on the Internet.
reconstruct the image on the server.
This image must be sent to the client to be saved locally.
so I'd like it to appear a window where you assign the destination image
plus I'd like the rest of the application were not affected by this activity.
The application is yet on production.
Thank you very much for your response.
From the tests done I get this error: java.lang.IllegalStateException: getWriter () has Already Been Called for this response.
In other words, you were trying to mix the binary data of the image with the character data of the HTML output, or you were trying to do this in a JSP instead of a Servlet. This is indeed not going to work. You need to send either the image or the HTML page exclusively in response to fully separate requests.
In your JSP/HTML page just have a link to the image, like so:
click to download image
Then, in a servlet listening on an url-pattern of /imageservlet/*, you just get the image as InputStream from some datasource (e.g. from local disk file system as FileInputStream) and then write it to the OutputStream of the response the usual Java IO way.
You only need to set at least the Content-Disposition response header to attachment to make sure that the client get a Save As popup dialogue, else it will be displayed straight in the browser. Setting the Content-Type and Content-Length are also important so that the browser knows what the server is sending and can predict how long the download may take.
response.setHeader("Content-Type", getServletContext().getMimeType(file.getName()));
response.setHeader("Content-Length", String.valueOf(file.length()));
response.setHeader("Content-Disposition", "attachment;filename=\"" + file.getName() + "\"");
You can find complete basic servlet example in this article.
Note: you cannot control where the client would save the image, this would be a security hole. This way websites would be able to write malicious files on client's disk unaskingly.
Update: as per your update, there are two options:
You need to let the client itself fire two HTTP requests (I've answered this in your subsequent question)
Create a client side application which does all the task directly at the client side and then embed this in your webpage, for example a Java Applet. With an applet you have full control over the client environment. You can execute almost all Java code you'd like to execute and you can write files to disk directly without asking client for the location to save. You only need to sign the applet by a 3rd party company or the client needs to confirm a security warning before running.
Its up to the browser how all types of output are handled. Web pages are given a content type of html which the browser understands and ends up rendering ass a page that we can see. Images are given content type of image/jpeg etc which are rendered as images when in a page etc. To force a download prompt one needs to use a content type of a binary file rather than that of an image so the browser forces the download rather than shows the image. To ensure this use something like "application/octetstream"... i cant recall exactly but its easy to google for.