I am writing a java client-server application where some clients have the right to put html files to serve as login pages on the server and the server will provide those pages to the rest of the users when they try to log. To this purpose I have added a preview button , that allows the admin set of clients to visualize the page when they upload it or afterwords . The problem I need to figure it out is how to open the browser to preview the file when the resource is not locally (it was uploaded by another admin and therefore it is remote).
Any suggestion and reference will be greatly appreciated !
Depends on the client; my first choice would be to use the Desktop class to make things simple, if you can guarantee Java 6.
If not, the Bare Bones Browser Launch plays some games on JRE < 6.
See this SO post for a bit more info.
If neither of those suits your purposes, you may need to provide some more info.
Related
I'm trying to code in a download in my java application. Basically, the user inputs their personal information, which is sent through file i/o to a text document. Then the next step is to have a series of buttons or links that corresponds to a certain download. For instance, button1=file1, button2=file2, and so on. I need it to download a picture. Is this possible through a dialog box? I'm running the application through a website. Any help is appreciated!
You can download a file from a URL using URLConnection. You can have your dialog box display the choices then choose a URL depending on what button they pressed, and use the URLConnection (via .connect() and .getInputStream()) to read the data, which you can then write out to a file or do whatever you want with.
You say you are running it through a web site, so I assume this is an applet. Bear in mind that if it is an unsigned applet you can only download files from the server that the applet is on. If you need to download from anywhere, you will need to sign your applet, or use something that isn't an applet.
Also, since you are running it through a web site, if it's appropriate perhaps a different approach is to just redirect the user to the URL of the file and let their browser take care of the download.
I would like to write a web application (in django) which scans the client/remote computers (assumption is windows) and retrieve the list of software's(mainly browsers) installed. Looking for suggestions to implement it.
Is this possible without asking the user to download any scritps/exe's?
If so, is it possible via java script?
I am planning to use python/django to write the entire app. Any input would be much appreciated.
EDIT : Comments on feasibility in java also much appreciated
Short answer: No, it is not possible
Long answer: This is something that any sane (operating) system designer / administrator would try to prevent - scanning of local system by a web page. However, you could use a plug-in component, such as a java applet, to do so - but in practice you probably would need to handle each client platform (OS) separately, since each of them has a different way of storing the information of installed software
You want to access the data from the client side so from the conceptual/logically its not good to access the client system. You have to use some medium which run on client side on behalf of server.
JavaScript and JavaApplet is good in this. You can get the data by JavaScript or Applet and in backend you can send data to the server.
You cannot do this unless you have some signed control installed on the client computer; or have them download a program which runs (separate from a browser) and sends the information to your server, where your django app can access it.
This is not possible using javascript (as it runs in a sandbox).
"Scanning" a client from a server may be possible if you break their security or get them to break it for you through some extension (see windows udate, for example). Either way, it's evil.
I have a need to "pop up" operating system folders from my web app, mostly to locate files in them. My users don’t want to use a conventional web upload/download paradigm. I have 7 or 8 static folders that need to be opened in explorer on a PC or in Finder on a mac. These folders are all network available, but are buried, and for convenience need to be shown on a web page.
There are IE tricks to do this, and I've written a sample flash app that only allows the browser to open, but I know most browsers sandbox this, and keep me from calling these folders. I am aware that some Java libraries deal with the opening of folders, does anyone have any thoughts or samples for this?
The only way I can imagine is to create a Signed Java Applet.
Applets cannot access the filesystem (and a lot of other ressources) if they are not valid signed. Maybe you can also grant the permission by a policyfile.
There ist a tutorial at JavaRanch.
But I am not sure, if this solution will be very helpful, because the JavaPlugin will be removed from a lott of browsers in near future. (I think FireFox already removed it).
I think there is actually NO solution to this problem.
There may be some workarrounds:
Put a Batch-File onto the server, which opens the folder, if executed
Can you create a local service, which handles requests from you webpage and opens the folder.
Create a webapplication, which opens the folder at serverside, and create a webpage, which displays the content in you website.
Wondering if anyone knows if there is a way to "return" something from a java web start application into the code on the website. For example say the user needed to select a location in the java application. This would then pass the location value back to the code on the webpage (which is php and javascript). I have figured out how to pass arguments into a program, but so far cannot figure out any way to get them out after much googling. Any help would be much appreciated, thanks.
In principle no, since the Webstart application can be running without any Website open at all.
But if your clients use the Java-plugin from 1.6.0_10 or later (and not Safari and some other browsers with special Java-handling), you can use a JNLP-enabled applet, which is able to do the same things as a Webstart application (i.e. loading files and such), and is always bound to a webpage. It then can use the Javascript-bridge, or simply a loadDocument with the right parameters to feed back information.
You can use URL or sockets to connect back to the "same-origin" host. You can also use BasicService to open a web page, possibly from a different server, in a browser (although this shouldn't be used to send information back, as it'll be a GET not a POST).
I am really looking for implementation advice as I have entered a new realm that I am not familiar with.
At the simplest level, I would like to find a way that I can read/write to a users machine from my web server. For this to work, I think I will have to install some sort of "plugin" on the users machine which can receive (or poll?) the server for instructions.
The above is the line of thought that I currently have, maybe using JAVA to do this. This needs to work on Linux, Mac and Windows OS.
I am really looking for advice on the above, is it a good idea? Is there a better way of doing this? Is there something out there already that I can build on top of?
I really appreciate all input and advice as this is something I have not done before.
Thanks all
For Java, you could launch a client application via Java Web Start that will be able to perform a limited set of operations on the file system.
If this is too restrictive, then you would need to provide a link to a download of a client application that would be installed / executed on the user's desktop machine.
I'm assuming you want to read and write specific files on the users' machine that are not normally accessible (i.e. not temp files, or files in a sandbox). And you want to do this from your webserver.
As you looking for cross platform, I'd go with java. Given that your needs are simple (read/write files from remote commands) you could probably target JRE 1.4, which is now many years old, but is installed on ca. 98% of desktops (source).
Here's an overview of how you can approach this:
Create a java applet or Java Web Start application that fetches a list of commands from a URL. The URL can contain any specific identification that you need to identify the machine, such as the users ID (see below for alternatives.)
Your webserver generates the list of commands that the applet should execute - create file, read file, write file and sends these as the response.
Sign the applet/application, so that it can escape the restrictions of the sandbox. To do this, you need to obtain a certificate. More on this later.
Inform and educate your users about what the applet is doing. E.g. a page on your site about why they are being asked to trust your certificate and what the implications are.
You can implement this as an applet or an application, the bulk of the work is pretty much the same. I talk about applet, but remember it applies equally to application.
In more detail:
The applet requests a list of commands from a URL. To hamper attempts at using your applet on another malicious site, you should use HTTPS to fetch the list of commands so that the server is authenticated. The URL should be hard-coded into your applet, so that any attempts to change this will break the signing. How you communicate the commands to the applet via the URL is up to you, e.g. you can use XML or use RMI and simply send over the list of commands as an object.
I mentioned using the userid to identify the machine - using the machine's MAC address is also a possibility. See how to get the mac address of the host.
Once you have the list of commands, your applet executes these using java file I/O apis. See File, FileReader/FileWriter in the javadocs. You include appropriate logging so the applets actions can be audited later if necessary. Once the applet has executed the commands, it sends the result of the commands back to the server, either as a POST operation, or another RMI method call, if you settle on RMI.
If you want to continually send commands from the server, then the applet can poll the URL/invoke the RMI method regularly. A Timer can help with this.
With communciation errors, it will be necessary for the client to request the list of commands more than once. Thus each time you produce a list of commands from the server, it is given an id. The server gives out the same list with the same id until it receives acknowledgement from the applet that the commands have been executed.
To sign the applet, you should obtain an rsa certificate from a certficiate authority. You can self-sign, but then you are opening the door to others modifying your app and impersonating your certificate. Details on obtaining and using certificates are given here.
If you don't know java, then all of this may not make a huge amount of sense, and it's not a trivial project to get started on, particularly considering the implications for your users if your implementation has holes and defects.
It may be wise to exercise caution: although you can do this, doesn't necessarily mean you should. I imagine that most expert users would frown on the use of this app, and would not accept the certificate. And then there is culpability - if your app accidentally deletes a critical file through a bug, misconfiguration, human error etc, how will you be prepared for that?
For the user, a web browser plugin may be the easiest, since the user won't have to manage yet another running application, however it has its limitation such as having to develop a plugin for each browser. In addition, the user would need their browser running.
You could have the user install a desktop application, which they would have to keep running, so installing it as a service might be ideal.
You could also use a plugin as a wedge between the web browser and a desktop application, which is how Flash works.
To really know you will have to answer the "why" question, why do you wan tot do this.
If you are just trying to store some state on the user's machine that you need to have locally then for small things you can fall back on cookies, or for larger needs you can use the new Web Database features in HTML5 http://dev.w3.org/html5/webdatabase/
If you need to access specific files then you are actually going to have to circumvent the security sand boxing that Java does when run on a webpage. I will leave that for others to go into, I don't know how to do it off hand myself.
In my opinion, Applet will be a better solution. I have made one applet which downloads a zip file from the server on client machine into temp folder, extracts the zip file into a directory specified by client (browser user) and then deletes the zip file.
thanks.
The lowest hanging fruit might be to provide WebDAV access through your web server to a given set of files, as this allows the users to see the files as a part of their usual filesystem with all their usual tools. You then do not have to do all that functionality.
Looks like Slide can deploy on Tomcat, and JBoss has ModeShape.
Will that be useful enough?